Fault protection circuits and methods

Abstract

In an embodiment, a device includes: a transistor having a first terminal and a control terminal; continuous operating loss (COL) fit circuitry (715, 735) having an input and an output; current sense circuitry (720, 740) having a first input, a second input, and an output, the first input of the current sense circuitry (720, 740) coupled to the first terminal of the transistor and the input of the COL fit circuitry (715, 735), the second input of the current sense circuitry (720. 740) coupled to the control terminal of the transistor; and comparator circuitry (725, 745) having a first input and a second input, the first input of the comparator circuitiy (725, 745) coupled to the output of the COL fit circuitry (715, 735), the second input of the comparator circuitry (725, 745) coupled of the output of the current sense circuitry (720, 740).

Description

FAULT PROTECTION CIRCUITS AND METHODS

[0001] The present description relates generally to an electronic system and method, and, in particular embodiments, to a fault protection circuit and method.BACKGROUND

[0002] Electronic systems utilize amplifiers for a wide range of operations. One example use for an amplifier is signal modulation. In modulation circuitry, the amplifier uses an input signal to drive transistors. The amplifier sequences the supply of power by the transistors to produce a relatively complex signal. For example, an amplifier produces a relatively high-power signal by using a relatively low power signal to drive transistors. Such transistors can drive relatively complex loads despite complex operating conditions, such as high switching speeds, voltages, etc.SUMMARY

[0003] In accordance to an embodiment, a device includes: a transistor having a first terminal and a control terminal; continuous operating loss (COL) fit circuitry' having an input and an output; current sense circuitry having a first input, a second input, and an output, the first input of the current sense circuitry coupled to the first terminal of the transistor and the input of the COL fit circuitry, the second input of the current sense circuitry coupled to the control terminal of the transistor; and comparator circuitry having a first input and a second input, the first input of the comparator circuitry coupled to the output of the COL fit circuitry, the second input of the comparator circuitry coupled of the output of the current sense circuitry.

[0004] In accordance to an embodiment, a device includes: a transistor; and load diagnostic circuitry coupled to the transistor, the load diagnostic circuitry configured to: determine a drain-to-source voltage of the transistor; determine a drain current of the transistor; determine a continuous operating loss (COL) current of the transistor using the drain-to-source voltage; compare the drain current to the COL current; and determine an operating condition of the transistor responsive to the comparison.

[0005] In accordance to an embodiment, a device includes: filter circuitry'; first amplifier circuitry coupled to the filter circuitry; second amplifier circuitry coupled to the filter circuitry and the first amplifier circuitry; and load diagnostic circuitry coupled to the second amplifier circuitry, the load diagnostic circuitry configured to determine a continuous operating loss(COL) current using voltages of the second amplifier circuitry.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] For a more complete understanding of the present description, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0008] FIG. 1 is a block diagram of example multi-class modulation circuitry’ including example class D amplifier circuitry and example class AB amplifier circuitry, according to an embodiment of the present description;

[0009] FIG. 2 is a block diagram of an example of the multi-class modulation circuitry’ including examples of the class D amplifier circuitry and the class AB amplifier circuitry of FIG. 1. according to an embodiment of the present description;

[0010] FIG. 3 is a schematic diagram of an example of the class AB amplifier circuitry’ of FIGs. 1 and 2 including example transistors and example load diagnostic circuitry', according to an embodiment of the present description;

[0011] FIG. 4 is a block diagram of an example of the load diagnostic circuitry’ of FIG. 3 including example continuous operating loss (COL) monitor circuitry for directly shutting down the amplifier circuitry of FIGS. 1, 2, and 3, according to an embodiment of the present description;

[0012] FIG. 5 is a flowchart representative of example machine-readable instructions or example operations that may be at least one of executed, instantiated, or performed using an example implementation of the COL monitor circuitry of FIG. 4 or more generally the load diagnostic circuitry of FIG. 3, according to an embodiment of the present description;

[0013] FIG. 6 is a plot of an example COL curve of the transistors of FIG. 3, according to an embodiment of the present description;

[0014] FIG. 7 is a block diagram of an example of the COL monitor circuitry of FIG. 4, according to an embodiment of the present description;

[0015] FIG. 8 is a flowchart representative of example machine-readable instructions or example operations that may be at least one of executed, instantiated, or performed using an example implementation of the COL monitor circuitry of FIGS. 4 and 7 or more generally the load diagnostic circuitry of FIGs. 3 and 4, according to an embodiment of the present description;

[0016] FIG. 9 is a timing diagram of an example operating conditions of the transistors of FIG. 3 or more generally the amplifier circuitry of FIGs. 1, 2, and 3, according to an embodiment of the present description;

[0017] FIG. 10 is a timing diagram of example temperatures of the transistors of FIG. 3 operating beyond the COL curve of FIG. 6, according to an embodiment of the present description;

[0018] FIG. 11 is a plot of an example temperature of the transistors of FIG. 3 during operations beyond the COL curve of FIG. 6, according to an embodiment of the present description;

[0019] FIG. 12 is a block diagram of example temperatures of an example integrated circuit (IC) implementing the transistors of FIG. 3 or more generally the amplifier circuitry of FIGS.1, 2, and 3 or even more generally the multi -class modulation circuitry of FIGs. 1 and 2, according to an embodiment of the present description;

[0020] FIG. 13 is a block diagram of another example of the load diagnostic circuitry’ of FIGs. 3 and 4 including example COL monitor circuitry’ for dynamically adjusting an overtemperature threshold, according to an embodiment of the present description;

[0021] FIG. 14 is a block diagram of the COL monitor circuitry' of FIG. 13 including example high-side detection circuitry, example low-side detection circuitry’, and example level monitor circuitry, according to an embodiment of the present description;

[0022] FIG. 15 is a schematic diagram of an example of the high-side detection circuitry of FIG. 14, according to an embodiment of the present description;

[0023] FIG. 16 is a schematic diagram of an example of the low-side detection circuitry of FIG. 14, according to an embodiment of the present description;

[0024] FIG. 17 is a schematic diagram of an example of the level monitor circuitry of FIG.14, according to an embodiment of the present description;

[0025] FIG. 18 is a plot of different levels of example COL curves corresponding to different operating conditions of the transistors of FIG. 3, according to an embodiment of the present description;

[0026] FIGS. 19A and 19B form a flowchart representative of example machine-readable instructions or example operations that may be at least one of executed, instantiated, or performed using an example implementation of the COL monitor circuitry of FIGS. 13 and 14 or more generally the load diagnostic circuitry of FIGs. 3 and 13, according to an embodiment of the present description;

[0027] FIG. 20 is a timing diagram of example operations of the COL monitor circuitry' of FIGs. 13 and 14, according to an embodiment of the present description; and

[0028] FIG. 21 is a block diagram of another example of the load diagnostic circuitry’ of FIGs. 3, 4, and 13 including example COL monitor circuitry for dynamically adjusting anovertemperature threshold and directly shutting down the transistors of FIG. 3, according to an embodiment of the present description.

[0029] Corresponding numerals and symbols in different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate relevant aspects of preferred embodiments and are not necessarily drawn to scale.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0030] The making and using of the embodiments are described in detail below. However, the present description provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments described are merely illustrative of specific ways to implement and use the description, and do not limit the scope of the description.

[0031] The description below' illustrates various specific details to provide an in-depth understanding of several examples according to the description. The embodiments may be obtained without one or more of the specific details, or with other methods, components, materials and the like. In some cases, known structures, materials or operations are not shown or described in detail so as not to obscure the different aspects of the embodiments. References to ‘'an embodiment” in this description indicate that a particular configuration, structure or feature described in relation to the embodiment is included in at least one embodiment. Consequently, phrases such as “in one embodiment” that may appear at different points of the present description do not necessarily refer exactly to the same embodiment. Furthermore, specific formations, structures or features may be combined in any appropriate manner in one or more embodiments.

[0032] Several aspects of the description are described below' with reference to example applications for illustration. Numerous specific details, relationships, and methods are set forth to provide an understanding of the description. The present description is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and / or concurrently with other acts or events.

[0033] Some embodiments relate to methods and apparatus to operate a transistor based on a continuous operating loss (COL).

[0034] Electronic systems utilize amplifiers for a wide range of operations. One example use for an amplifier is signal modulation. In modulation circuitry, the amplifier uses an input signal to drive transistors. The amplifier sequences the supply of power by the transistors to produce a relatively complex signal. For example, an amplifier produces a relatively high-power signal by using a relatively low power signal to drive transistors. Such transistors can drive relativelycomplex loads despite complex operating conditions, such as high switching speeds, voltages, etc.

[0035] One instance of modulation circuitry utilizes class AB amplifier circuitry to supply a signal to a load. Class AB amplifier circuitry may utilize a sinusoidal waveform to control transistors of power stage circuitry. In some class AB amplifier circuitry, positive amplitudes drive a first transistor while negative amplitudes drive a second transistor. The first and second transistors generate the output of the class AB amplifier circuitry at a shared terminal. In such examples, the output of the class AB amplifier circuitry is an amplified version of the input signal. The output of the class AB amplifier circuitry is considered a linear output. Such linear outputs have a relatively high electromagnetic interference (EMI) immunity and may drive a load without inductor capacitor (LC) filter circuitry. However, driving the transistors of the class AB amplifier circuitry to generate a linear output has a relatively low power efficiency compared to alternative methods of modulation.

[0036] In continuous operation of an amplifier operating in the linear region, such as a class AB amplifier, the temperature of the transistors continues to increase responsive to the relatively low power efficiency. In such operation, if the temperature of the transistors increases beyond an overtemperature threshold, the transistors can achieve a thermal runaway condition. Thermal runaway may result in silicon and metallization failures of the amplifier. Transistors undergoing thermal runaway (also referred to as positive thermal feedback) produce an increasing current and excessive heat. If left unchecked, thermal runaway can permanently damage a transistor.

[0037] In an attempt to reduce a likelihood of thermal runaway, some linear (e.g., class AB) amplifiers may include temperature monitor circuitry or current limiting circuitry. The temperature monitor circuitry disables the transistors or more generally the amplifier circuitry in response to sensing a temperature in excess to an over temperature threshold. The cunent limiting circuitry limits the current of transistors of the class AB amplifier circuitry. However, in some examples, a weak short across one of the transistors produces unintentional power consumption by the transistors. In some such examples, such as relatively low resistance shorts, the temperature monitor circuitry and the current limiting circuitry do not respond quick enough to prevent thermal runaway.

[0038] In some devices, such as in some audio devices, the current limiting circuitry may distort the output responsive to limiting the current through the transistors.

[0039] Some embodiments relate to operating a transistor based on a continuous operating loss (COL) using COL monitor circuitry. In some embodiments, load diagnostic circuitrymonitors operating conditions of transistor(s) or more generally amplifier circuitry to prevent thermal runaway. In some examples, the load diagnostic circuitry includes COL monitor circuitry and temperature monitor circuitry. The COL monitor circuitry senses the drain-to-source voltage (VDS) of a transistor. The COL monitor circuitry uses the drain-to-source voltage (VDS) and a COL curve to determine a COL current. The COL curve is a function representing safe operating conditions of the transistor. In some examples, the COL curve is a function of the drain-to-source voltage (VDS) and current (ID) of the transistor. In some such examples, the COL curve defines a threshold operating voltage and currents for the transistor to continue to safely operate. Advantageously, COL curves may be used to limit a load of the amplifier circuitry, e.g., by defining device specific operating voltage and current thresholds. Such COL curves can be below manufacturer recommended thresholds of the transistor to increase a likelihood of safely operating.

[0040] In some embodiments, the COL monitor circuitry determines the COL current as the corresponding current of the COL curve for the determined gate-to-source voltage (VGS). The COL monitor circuitry compares the determined COL cunent to the current (ID) flowing through the transistor. In some such example operations, if the current (ID) flowing through the transistor is less than the determined COL current, the COL monitor circuitry determines the transistor can continue to operate. However, if the current (ID) flowing through the transistor is greater than the determined COL current, the COL monitor circuitry determines the operations of the transistor need to be limited to prevent thermal runaway. For example, if the transistor continues to operate beyond the COL current, the COL monitor circuitry may disable the transistor or more generally the amplifier circuitry. In another example, if the transistor continues to operate beyond the COL current, the COL monitor circuitry may adjust the overtemperature threshold of the temperature monitor circuitry. In such examples, decreasing the overtemperature threshold, decreases the response time of temperature monitor circuitry to rising a temperature.

[0041] In some embodiments, the COL monitor circuitry advantageously uses the COL curve to detect adverse operating conditions of a transistor. In some embodiments, the COL monitor circuitry advantageously determines a COL current using voltages of a transistor. In some embodiments, the COL monitor circuitry may advantageously disable a transistor responsive to detecting a current exceeding the COL current for a given drain-to-source voltage (VDS). In some embodiments, the COL monitor circuitry may advantageously allow a transistor to continue to operate at a current exceeding the COL current for a duration of time. In some embodiments, the COL monitor circuitry advantageously considers the voltage, current, andduration of time, which are the factors that correspond to the temperature of a transistor, in monitoring the safe operations of a transistor. In some embodiments, the COL monitor circuitry advantageously detects shorts across the transistor as a current (ID) greater than the COL current. In some embodiments, the COL monitor circuitry advantageously improves the response time of overtemperature detection by dynamically changing the overtemperature threshold.

[0042] FIG. 1 is a block diagram of audio system 100, according to an embodiment of the present description. Audio system 100 includes an audio source 105, multi-class modulation circuitry 110, first conditioning circuitry 115, a first resistor 120, a second resistor 125, first amplifier circuitry 130. second conditioning circuitry' 135, second amplifier circuitry' 140, filter circuitry 150, a speaker 160. and aline out 170.

[0043] In example operations, the audio system 100 produces audible sound responsive to input signals (INP, INM) from the audio source 105. In such examples, the input signals (INP, INM) represent an audio signal. In other examples, the audio system 100 supplies the audio signal to an external device to produce audible sound. In such examples, the line out 170 may be coupled to an auxiliary (AUX) connector, driver circuitry, alternative audio connector, communication link, etc.

[0044] In some embodiments, the multi-class modulation circuitry' 110 receives the input signals (INP, INM) from the audio source 105. The example multi-class modulation circuitry 110 of FIG. 1 includes the conditioning circuitry 115, 135, the resistors 120, 125, the amplifier circuitry 130, and the amplifier circuitry 140. In the example of FIG. 1, the multi-class modulation circuitry 110 implements single inductor (IL) modulation. IL modulation utilizes different classes of amplifier to produce asymmetric outputs. In the example of FIG. 1, the amplifier circuitry 130 is a class-D amplifier and the amplifier circuitry 140 is a class- AB amplifier. Advantageously, IL modulation allows modulation circuitry to balance benefits of different amplifier classes.

[0045] The amplifier circuitry 130 (e.g., a class-D amplifier) receives the input signals (INP, INM) and the output signal (OUTM) of the amplifier circuitry 140. In some examples, the conditioning circuitry 115 filters relatively high frequencies from the input signals (INP. INM). The resistors 120, 125 provide a current feedback path to the output signals (OUTP, OUTM) of the amplifier circuitry' 130, 140. The output signal (OUTM) of the amplifier circuitry' 140 forms a feedforward path with the amplifier circuitry' 140. The feedforward path may allow the amplifier circuitry 130 to adjust the output signal (OUTP) based on the amplifier circuitry 140. The output signal (OUTP) of the amplifier circuitry 130 is a relatively high speed PWMrepresentative of the difference between the input signals (INP, INM) and the output signals (OUTP, OUTM) of the amplifier circuitry 130, 140. Advantageously, using class-D modulation for the amplifier circuitry 130 reduces noise, improves efficiency, improves total harmonic distortion, etc. An example of the amplifier circuitry 130 is further illustrated and described in connection with FIG. 2.

[0046] The amplifier circuitry 140 (e.g., a class AB amplifier) receives the input signals (INP, INM). The example amplifier circuitry 140 of FIG. 1 includes load diagnostic circuitry 175, which further includes COL monitor circuitry 180. In some examples, the conditioning circuitry 135 filters relatively high frequencies from the input signals (INP, INM). In the example of IL modulation, the amplifier circuitry 140 amplifies the input signals (INP, INM) by a relatively high gain. Such a relatively large gain saturates the output signal (OUTM) of the amplifier circuitry 140 for a relatively large range of input voltages. Advantageously, during saturation the output of the amplifier circuitry 140 is non-linear, which has a relatively high power efficiency. However, if the input voltage is relatively small, such as near a common potential, the relatively high gain may not saturate the output signal (OUTM) of the amplifier circuitry 140. In such examples, the output signal (OUTM) of the amplifier circuitry 140 may be linear. Advantageously, the relatively high gain of the amplifier circuitry 140 decreases the range of input voltages that produce a linear output. Advantageously, the amplifier circuitry 130 compensates for non-linear piece wise operations of the output signal (OUTM) of the amplifier circuitry 140 using the feedback and feedforward paths to the amplifier circuitry 130.

[0047] During linear operations, the load diagnostic circuitry 175 monitors currents of the amplifier circuitry 140. In some examples, the COL monitor circuitry 180 determines if a short has formed in the amplifier circuitry 140 responsive to an excursion from a COL curve. Example COL curves are further illustrated and described in connection with FIGs. 6 and 18. In some examples, the load diagnostic circuitry 175 shuts down the amplifier circuitry 140 responsive to a detection of an excursion from the COL curve. Advantageously, the load diagnostic circuitry 175 may reduce the likelihood of relatively high currents during the linear mode damaging the amplifier circuitry 140. Examples of the load diagnostic circuitry 175 and the COL monitor circuitry 180 are further illustrated and described in connection with FIGs.4, 7, 13, 14, and 21.

[0048] In some embodiments, the filter circuitry 150 receives the output signals (OUTP, OUTM) of the amplifier circuitry' 130, 140. The filter circuitry' 150 may average the relatively high speed switching of the output of the amplifier circuitry 130 to produce a filtered sinusoidal signal. The filter circuitry 150 differentially couples the average of the output signal (OUTP)of the amplifier circuitry 130 to the output signal (OUTM) of the amplifier circuitry 140. The filter circuitry’ 150 drives one ofthe speaker 160 orthe lineout 170 using the differential voltage of the filtered output signals (OUTP, OUTM) of the amplifier circuitry 130, 140. Advantageously, the multi-class modulation circuitry 110 receives the relatively simple output of a class AB amplifier, which does not need an inductor to filter like the relatively complex output of class D amplifiers.

[0049] FIG. 2 is a block diagram of an example of the multi-class modulation circuitry 110 of FIG. 1, according to an embodiment of the present description. Multi-class modulation circuitry’ 110 includes the conditioning circuitry’ 115, 135, the resistors 120, 125, the amplifier circuitry 130, 140, the load diagnostic circuitry' 175, and the COL monitor circuitry 180. In the example of FIG. 2. the multi-class modulation circuitry 110 includes the conditioning circuitry 115, 135, the resistors 120, 125, the amplifier circuitry 130, 140, modulator circuitry 220, combination circuitry 225, feedforward circuitry’ 230, PWM generation circuitry' 235, first output stage circuitry' 240, pre-amplifier circuitry 260, gate driver circuitry’ 265, and second output stage circuitry 270. Although in the example of FIG. 1. the multi-class modulation circuitry 110 is implemented in the audio system 100, the multi -class modulation circuitry 110 may be implemented in alternative implementations, such as driving loads that are not speakers. Advantageously, using the multi-class modulation circuitry’ 110 in such alternative implementations may use the filter circuitry 150, which may reduce system on chip size and cost by using a single inductor.

[0050] In the example of FIG. 2, the amplifier circuitry 130 includes the modulator circuitry 220, the combination circuitry' 225, the feedforward circuitry' 230, the PWM generation circuitry 235, and the first output stage circuitry' 240. In the example of FIG. 2, the amplifier circuitry 140 includes the load diagnostic circuitry 175, the COL monitor circuitry 180, the gate driver circuitry 265, and the second output stage circuitry 270. Another example of the amplifier circuitry 140 is illustrated in FIG. 3.

[0051] The example filter circuitry' 150 of FIG. 2 includes an example inductor 272, a first example capacitor 275, and a second example capacitor 280.

[0052] In example operations of the amplifier circuitry 130, resistances of the conditioning circuitry 115 and the resistors 120, 125 may combine the input signals (INP, INM) and feedback currents from the output signals (OUTP, OUTM) of the amplifier circuitry' 130, 140. The modulator circuitry 220 receives currents representing the difference between the input signals (INP. INM) and the output signals (OUTP. OUTM) of the amplifier circuitry 130. 140. The modulator circuitry 220 uses a transfer function to the currents representing the errorsbetween the input signals (INP, INM) and the output signals (OUTP, OUTM) of the amplifier circuitry 130, 140. In some examples, the modulator circuitry 220 implements a multi-order transfer function. In some such examples, the modulator circuitry 220 produces a series of outputs representing the error between the input signals (INP, INM) and the output signals (OUTP, OUTM) of the amplifier circuitry 130, 140 across the multiple orders of the transfer function. The combination circuitry 225 combines the outputs of the modulator circuitry 220 and the feedforward circuitry 230 to produce an error signal. The feedforward circuitry 230 combines the error signal with the output signal (OUTM) of the amplifier circuitry. Advantageously, the feedforward circuitry 230 accounts for linear operations of the output signal (OUTM) of the amplifier circuitry 140. Advantageously, the feedforward circuitry' 230 accounts for non-ideal linear operations by offsetting the combined error signals by the output signal (OUTM) of the amplifier circuitry 140.

[0053] In some such example operations of the amplifier circuitry 130, the PWM generation circuitry 235 compares the error signal from the combination circuitry 225 to a carrier signal. The PWM generation circuitry 235 generates a square waveform having a duty cycle that represents the comparison of the error signal to the carrier signal. In some examples, the carrier signal is a double edge symmetric triangular signal having a frequency referred to as a switching frequency. In some such examples, the switching frequency of the carrier signal is substantially greater than a resonant frequency of an LC filter of the inductor 272 and the capacitor 275. For example, if the error signal is greater than the triangular signal, the PWM generation circuitry 235 sets the output to a logic high (e g., logical one). In such examples, if the error signal is less than the triangular signal, the PWM generation circuitry 235 sets the output to a logic low (e.g., logical zero). The PWM generation circuitry 235 produces a square wave at the switching frequency having a duty cycle that represents the linear value of the error signal. The output stage circuitry 240 converts the logic levels of the square wave to produce the output signal (OUTP) of the amplifier circuitry 130. In some examples, the output stage circuitry' 240 sets the output signal (OUTP) of the amplifier circuitry' responsive to controlling transistors using the square wave from the PWM generation circuitry 235. Advantageously, driving transistors using a square wave reduces linear operations by setting the transistors to the triode region, which corresponds to being fully on, opposed to in the saturation region. Advantageously, driving transistors of the output stage circuitry 240 in the triode region has a relatively high power efficiency.

[0054] In example operations of the amplifier circuitry 140, the pre-amplifier circuitry 260 receives the input signals (INP, INM) from the conditioning circuitry 135. The pre-amplifiercircuitry 260 amplifies the input signals (INP, INM) by a relatively high gain. The gate driver circuitry 265 shifts the logic levels of the amplified input signals. Example operations of the pre-amplifier circuitry 260 and the gate driver circuitry 265 are further described in connection with FIG. 3.

[0055] In some embodiments, the output stage circuitry 270 sets the output signal (OUTM) of the amplifier circuitry 140 using the outputs of the gate driver circuitry 265. In some examples, the output stage circuitry 270 sets the output signal (OUTM) of the amplifier circuitry 140 responsive to controlling transistors using the outputs of the gate driver circuitry 265. An example of the output stage circuitry 270 is further illustrated and described in connection with FIG. 3.

[0056] In example operations of the amplifier circuitry 140, the load diagnostic circuitry 175 monitors currents of the output stage circuitry 270. In some examples, the COL monitor circuitry 180 determines if a short has formed in the output stage circuitry 270 responsive to an excursion from a COL curve. Example COL curves are further illustrated and described in connection with FIGs . 6 and 18.

[0057] In some examples, the load diagnostic circuitry 175 shuts down the output stage circuitry 270, the amplifier circuitry 140 and / or the audio system 100 responsive to a detection of an excursion from the COL curve. Advantageously, the load diagnostic circuitry 175 reduces the likelihood of relatively high currents and voltages or, more generally, energy consumption damaging the amplifier circuitry 140. Examples of the load diagnostic circuitry 175 and the COL monitor circuitry 180 are further illustrated and described in connection with FIGs . 4, 7, 13, 14, and 21.

[0058] In example operations of the filter circuitry 150, the inductor 272 receives the output signal (OUTP) of the amplifier circuitry 130, which is a relatively high frequency PWM signal. The inductor 272 and the capacitor 275 average the relatively high frequency switching of the output signal (OUTP) of the amplifier circuitry 130. The capacitor 275 couples the average of the output signal (OUTP) of the amplifier circuitry 130 to the output signal (OUTM) of the amplifier circuitry 140. The capacitor 280 filters relatively high frequency signals at the output signal (OUTM) of the amplifier circuitry 140. Advantageously, the capacitor 280 reduces total harmonic distortion (THD), electromagnetic interference (EMI), etc. Advantageously, the filter circuitry 150 does not have an intervening inductor between the output signal (OUTM) of the amplifier circuitry 140 and the speaker 160. Advantageously, decreasing the number of inductors in the filter circuitry 150 reduces the cost and size of the audio system 100.

[0059] FIG. 3 is a schematic diagram of an example of the amplifier circuitry 140 of FIGs.1 and 2, according to an embodiment of the present description. In the example of FIG. 3, the amplifier circuitry 140 includes the load diagnostic circuitry 175, the COL monitor circuitry 180, pre-amplifier circuitry 260, the gate driver circuitry 265, and the output stage circuitry 270. The gate driver circuitry 265 of FIG. 2 includes a first amplifier 305 and a second amplifier 310. The output stage circuitry 270 of FIG. 2 includes a first transistor 315 and a second transistor 320. In some examples, such as in FIG. 3, the amplifier circuitry 140 also includes a temperature sensor 330.

[0060] The amplifier circuitry 140 receives the input signals (INP, INM). In some examples, the amplifier circuitry 140 is a class AB amplifier. Class AB amplifiers are linear amplifiers that produce an output between a high and low side supply voltages. In example IL operations, as further described in connection with FIG. 1 , the amplifier circuitry 140 has a relatively high gain to saturate the output signal (OUTM). In such example operations, the amplifier circuitry 140 operates in a linear region during the transition between saturated output states. Advantageously, saturating the output signal (OUTM) of the amplifier circuitry 140 increase power efficiency.

[0061] The pre-amplifier circuitry 260 receives the input signals (INP, INM). The preamplifier circuitry 260 amplifies the input signals (INP, INM) by a relatively high gain. The pre-amplifier circuitry 260 provides the amplified input signals to the gate driver circuitry 265.

[0062] In example operations of the gate driver circuitry 265. the amplifier 305 receives the amplified plus input signal (INP) from the pre-amplifier circuitry 260. The amplifier 305 shifts the logic levels of the plus input signal (INP) to voltages in relation to the source voltage of the transistor 315. The amplifier 310 receives the amplified minus input signal (INM) from the pre-amplifier circuitry 260. The amplifier 310 shifts the logic levels of the minus input signal to voltages in relation to the source voltage of the transistor 320. Advantageously, the amplifiers 305, 310 allow the plus and minus input signals (INP, INM) to drive the transistors 315, 320.

[0063] In example operations of the output stage circuitry 270, the transistors 315, 320 have a first terminal (e.g., drain terminal), a second terminal (e.g., source terminal), and a control terminal (e.g., gate terminal). The transistor 315 regulates the supply of power from the output power supply (PVDD) based on the amplifier 305. The transistor 320 regulates the supply of power from the output signal (OUTM) of the amplifier circuitry 140 to the common terminal, which provides a common potential (e.g., ground. AVSS. etc.), based on the amplifier 310. In some examples, the transistors 315, 320 are referred to as a power stage. In such examples, thetransistor 315 may be referred to as a high-side transistor and the transistor 320 may be referred to as a low-side transistor.

[0064] In the example of FIG. 3, the transistors 315, 320 are n-channel metal-oxide semiconductor field-effect transistors (MOSFETs). Alternatively, the transistors 315, 320 may be n-channel field-effect transistors (FETs), n-channel insulated-gate bipolar transistors (IGBTs), n-channel junction field effect transistors (JFETs), NPN bipolar junction transistors (BJTs) or, with slight modifications, p-type equivalent devices. The transistors 315, 320 may be depletion mode devices, drain-extended devices, enhancement mode devices, natural transistors or other type of device structure transistors. Furthermore, the transistors 315, 320 may be implemented in / over a silicon substrate (Si), a silicon carbide substrate (SiC), a gallium nitride substrate (GaN) or a gallium arsenide substrate (GaAs).

[0065] In example operations, the load diagnostic circuitry 175 monitors of the transistors 315, 320. In some examples, the load diagnostic circuitry 175 detects unsafe operating conditions of the transistors 315, 320. In such examples, the load diagnostic circuitry 175 may shut down the transistors 315, 320, the amplifier circuitry 140. and / or the audio system 100, e.g., to prevent damage. For example, the load diagnostic circuitry 175 may shut down the amplifier circuitry 140 responsive to a determination that the current being supplied by either of the transistors 315, 320 exceeds a COL curve. In such examples, the COL curve represents the current and voltage conditions of the transistors 315, 320 likely to cause thermal runaway.

[0066] In some example operations, the load diagnostic circuitry 175 uses the temperature sensor 330 to sense adverse thermal conditions of the transistors 315, 320. For example, the load diagnostic circuitry 175 may compare a temperature from the temperature sensor 330 to an over temperature threshold to detect adverse operating temperatures of the transistors 315, 320. In some examples, as further illustrated and described in connection with FIG. 12, the temperature sensor 330 is positioned in proximity to components that tend to consume more power, such as the transistors 315, 320. In such examples, the placement of the temperature sensor 330 increases the response time of the load diagnostic circuitry 175 to dangerous operating temperatures. Advantageously, the load diagnostic circuitry 175 monitors the transistors 315, 320 for adverse operating conditions. Examples of the load diagnostic circuitry 175 are further illustrated and described in connection with FIGs. 4, 13, and 21.

[0067] FIG. 4 is a block diagram of an example implementation of the load diagnostic circuitry 175 of FIG. 3, e.g., to safely operate the transistors 315, 320 of FIG. 3, according to an embodiment of the present description.

[0068] In some embodiments, load diagnostic circuitry' 175 may be implemented using a processor or controller coupled to a memory and configured to execute instructions from such memory. Some embodiments may be implemented or include a central processor unit (CPU), a field programmable gate array (FPGA), a hardware accelerator, and / or a state machine. In some embodiments, load diagnostic circuitry 175 is implemented with synthesized logic. In some embodiments, load diagnostic circuitry 175 is implemented in hardware only. In some embodiments, load diagnostic circuitry 175 is configurable via registers. Other implementations may also be possible.

[0069] In the example of the FIG. 4, the load diagnostic circuitry 175 includes the COL monitor circuitry 180, temperature monitor circuitry 420, and shutdoyvn circuitry 430.

[0070] The load diagnostic circuitry 175 receives the gate, source, and drain voltages of the transistors 315, 320. In the example of FIG. 4, the load diagnostic circuitry 175 receives the output signal of the amplifier circuitry 140, the output supply voltage (PVDD), a first gate-to-source voltage (VGS i) of the transistor 315, and a second gate-to-source voltage (VGS 2) of the transistor 320. The load diagnostic circuitry’ 175 may receive a temperature voltage (VTEMP) from the temperature sensor 330. In such examples, the temperature voltage (VTEMP) represents the temperature of the transistors 315, 320 or the amplifier circuitry 140.

[0071] In some embodiments, the COL monitor circuitry' 180 receives the voltages of the transistors 315, 320. The COL monitor circuitry 180 determines the current flowing through the transistors 315. 320 using the gate, source, and drain voltages. The COL monitor circuitry 180 determines a COL current or voltage of the transistors 315, 320 using the source and drain voltages. The COL current may be a threshold current corresponding to conditions that lead to thermal runaway. For example, the transistor 315 experiences thermal runaway after continuing to supply a current greater than the COL current. The COL monitor circuitry’ 180 produces a direct shutdown indication (DIRECT SHUTDOWN) responsive to operations of the transistors 315, 320 exceeding safe operating conditions. Examples of the COL monitor circuitry’ 180 are further illustrated and described in connection with FIGs. 7 and 14. In some examples, the COL monitor circuitry 180 is instantiated by ASIC or programmable circuitry executing COL monitor instructions to perform operations such as those represented by the flowcharts of FIGs. 5 and 8.

[0072] The temperature monitor circuitry’ 420 receives the temperature voltage (VTEMP) from the temperature sensor 330. The temperature monitor circuitry 420 compares the temperature voltage (VTEMP) to an over temperature threshold. In example operations, the temperature monitor circuitry 420 determines the transistors 315, 320 operate at potentially harmfultemperatures responsive to the temperature voltage (VTEMP) exceeding the over temperature threshold. The temperature monitor circuitry’ 420 produces a temperature shutdown indication (TEMP_SHUTDOWN) responsive to detecting excessive temperatures. In some examples, the temperature monitor circuitry 420 is instantiated by ASIC or programmable circuitry executing temperature monitor instructions to perform operations such as those represented by the flowchart of FIG. 5.

[0073] The shutdown circuitry 430 receives the direct shutdown indication (DIRECT SHUTDOWN) from the COL monitor circuitry 180 and the temperature shutdown indication (TEMP SHUTDOWN) from the temperature monitor circuitry' 420. The shutdown circuitry 430 shuts down the transistors 315, 320, the amplifier circuitry' 140, and / or the audio system 100 responsive to receiving either of the direct shutdown indication (DIRECT SHUTDOWN) or temperature shutdown indication (TEMP SHUTDOWN). Advantageously, the COL monitor circuitry 180 can produce the direct shutdown indication (DIRECT SHUTDOWN) before the temperature monitor circuitry 420 can sense a temperature increase. In some examples, the shutdown circuitry 430 is instantiated by ASIC or programmable circuitry executing shutdown instructions to perform operations such as those represented by the flowchart of FIG. 5.

[0074] FIG. 5 is a flowchart of embodiment method 500, according to an embodiment of the present description. Method 500 may be performed by load diagnostic circuitry 175 of FIGs.1, 2, 3, and 4.

[0075] Method 500 begin at Block 505 at which the temperature sensor 330 determines a temperature of the transistor. In example operations, the temperature sensor 330 senses the temperature of the transistors 315, 320 or more generally the amplifier circuitry' 140. In some examples, the temperature sensor 330 produces the temperature voltage (VTEMP) proportional to a junction temperature of the transistors 315, 320. Example placement of the temperature sensor 330 is further illustrated and described in connection with FIG. 12.

[0076] The temperature monitor circuitry’ 420 determines if the temperature of the transistor is greater than a threshold. (Block 510). In example operations, the temperature monitor circuitry 420 compares the temperature of the transistors 315, 320 to an over temperature threshold. In some examples, the over temperature threshold represents a safe operating temperature of the transistors 315, 320. In some such examples, the temperature monitor circuitry 420 determines the transistors 315. 320 are at risk of thermal runaw ay responsive to the temperature sensor 330 sensing a temperature greater than the overtemperature threshold.

[0077] If the temperature monitor circuitry' 420 determines that the temperature of the transistor is greater than the threshold (e.g., Block 510 returns a result of NO), the COL monitor circuitry 180 determines a continuous operating loss (COL) current of the transistor using voltages of the transistor. (Block 515). In example operations, the COL monitor circuitry 180 receives gate, source, and drain voltages (VG, VS, VD) of the transistors 315, 320. The COL monitor circuitry 180 determines a COL current for the current drain-to-source voltage (VDS). The COL current is a threshold representing a safe load range to continue to operate the transistor. In some examples, the COL current is a function of the drain-to-source voltage that is set using a safe operating area (SOA) of the transistors 315, 320. In some examples, a function representing the COL current for different drain-to-source voltages is provided or integrated by design. Such functions may include considerations for a maximum load current, a soft short (e.g., a short across the transistors 315, 320), etc.

[0078] The COL monitor circuitry7180 determines current of the transistor. (Block 520). In some examples, the COL monitor circuitry 180 replicates the current of the transistors 315, 320 using the gate, source, and drain voltages (VG, VS. VD). In some examples, the COL monitor circuitry 180 senses the replica current to determine the current of the transistors 315, 320 without effecting the output signal (OUTM) of the amplifier circuitry 140. Also, the replicated current may be scaled down to reduce power consumption.

[0079] The COL monitor circuitry 180 determines if the current of the transistor is greater than the COL current. (Block 525). In example operations, the COL current represents a threshold operating condition of the transistors 315, 320. In some examples, if the current through either of the transistors 315, 320 is less than the COL current, the transistors 315, 320 can continue to safely operate. In such examples, if the current through either of the transistors 315, 320 is greater than the COL current, continuing to operate the transistors 315, 320 at the same conditions risks thermal runaway. In some example operations, as further illustrated and described in connection with FIGs. 14, 17, 19A, and 19B, the COL monitor circuitry 180 includes timer circuitry7to allow the transistors 315, 320 to briefly operate beyond the COL current. In such examples, the timer circuitry adds a consideration for the energy (Q) associated with the temperature of the transistors 315, 320 over time. For example, the energy (Q) consumed by the transistors 315, 320 is approximately equal to the drain-to-source voltage times the current and the duration of time. In such examples, the temperature of the transistor 315, 320 increases with the energy (Q). If the COL monitor circuitry 180 detennines that the current of the transistor is not greater than the COL current (e.g., Block 525 returns a result of NO), control proceeds to return to Block 505.

[0080] If the temperature monitor circuitry' 420 determines that the temperature of the transistor is greater than the threshold (e.g., Block 510 returns a result of YES) or the COL monitor circuitry 180 determines the current of the transistor is greater than the COL cunent (e.g., Block 525 returns a result of YES), the shutdown circuitry7430 shuts down the transistor. (Block 530). In example operations, the shutdown circuitry7430 disables the transistors 315, 320, the amplifier circuitry 140 and / or the audio system 100 responsive to receiving one of the direct shutdown indication (DIRECT SHUTDOWN) or the temperature shutdown indication (TEMP SHUTDOWN). The COL monitor circuitry 180 generates the direct shutdown indication (DIRECT SHUTDOWN) responsive to the current of either of the transistors 315, 320 exceeding the determined COL current. The temperature monitor circuitry 420 generates the temperature shutdown indication (TEMP SHUTDOWN) responsive to the temperature of the transistors 315, 320 exceeding the over temperature threshold. In such example operations, the shutdown circuitry 430 may disable the transistors 315, 320 by clamping the gate-to-source voltages, disabling the input to the amplifier circuitry 140, etc.

[0081] Control proceeds to End. Example methods are described with reference to the flowchart illustrated in FIG. 5. However, many other methods of implementing the load diagnostic circuitry' 175 of FIGs. 3 and 4 may also be used in this description. For example, the order of execution of the blocks may be changed, or some of the blocks described may be changed, eliminated, or combined. Similarly, additional operations may be included in the manufacturing process before, in between, or after the blocks shown in the illustrated examples.

[0082] FIG. 6 is a plot 600 of an example COL curve 610 of the transistors 315, 320, according to an embodiment of the present description. In the example of FIG. 6, the plot 600 illustrates the COL curve 610, an example linear COL curve 620, and an example clamp region 630. The COL curve 610 is a function of a drain current (ID_MX) across a range of drain-to-source voltages (VDS_MX) for a given transistor (MX). In some examples, as further illustrated and described in connection with FIG. 7, the COL curve 610 plots the drain- to-source voltage (VDS_MX) of a transistor in terms of current (I(VDS_MX)) and a COL current (COL_ID_MX) across a range of safe operating currents of the transistor in terms of a COL voltage (V(COL_ID_MX)). In such examples, the COL monitor circuitry 180 produces the current (I(VDS_MX)) by converting the drain-to-source voltage (VDS_MX) of the transistor to a current. Similarly, the COL monitor circuitry 180 produces the COL voltage (V(COL ID MX)) by generating a voltage representation of the COL current (COL ID MX) for the drain-to-source voltage (VDS_MX).

[0083] The linear COL curve 620 is a linear approximation of the COL curve 610. In some examples, implementing the curvature of the COL curve 610 substantially increases the complexity of a device. In such examples, designers may implement the linear COL curve 620 as an approximation of the COL curve 610. Advantageously, the linear COL curve 620 reduces the integration complexity of the COL monitor circuitry 180. Additional examples of the COL curves 610, 620 are further illustrated and described in connection with FIG. 18.

[0084] The clamp region 630 represents a range of gate-to-source voltages (VGS_MX) where a transistor operates in a linear mode, which corresponds to the triode region of operation. In some examples, such as the amplifier circuitry 140, the transistors 315, 320 operate in linear mode when the output signal (OUTM) of the amplifier circuitry 140 is saturated. In such examples, as illustrated by the exponential increase in the COL curve 610, the transistors 315, 320 are capable of continuing to safely operate with relatively large drain currents (ID_MX) as the drain-to-source voltage (VDS_MX) decreases and the gate-to-source voltage increases. Advantageously, the transistors 315, 320 are unlikely to experience positive thermal feedback across continuing operations in the clamp region 630. Advantageously, the COL monitor circuitry 180 may limit monitoring to saturation operations of the transistors 315, 320, such as a transition between saturated states of the output of the amplifier circuitry 140. Advantageously, the clamp region 630 reduces the complexity' of the COL monitor circuitry' 180 by limiting monitoring operations to during saturation operations of the transistors 315, 320.

[0085] FIG. 7 is a block diagram of an example of the COL monitor circuitry 180 of FIG. 4, according to an embodiment of the present description. In the example of FIG. 7, the COL monitor circuitry' 180 includes first voltage-to-current (V-I) circuitry' 705, combination circuitry 710, first COL fit circuitry 715, first current sense circuitry 720, first comparator circuitry 725, second V-I circuitry 730, second COL fit circuitry 735, second current sense circuitry 740, second comparator circuitry^ 745, a first logic device 750, gate-to-source voltage (VGS) detect circuitry' 755, a second logic device 760, deglitch circuitry 765, and timer circuitry 770.

[0086] The COL monitor circuitry 180 receives the gate, source, and drain voltages (VG, VS, VD) of the transistors 315, 320. In the example of FIG. 3, the drain voltage (VD) of the transistor 315 is the output supply voltage (PVDD) and the source voltage (Vs) of the transistor 315 is the output signal (OUTM) of the amplifier circuitry' 140. In the example of FIG. 3, the drain voltage (VD) of the transistor 320 is the output signal (OUTM) of the amplifier circuitry 140 and the source voltage (Vs) of the transistor 320 is the common potential (e.g., ground, AVSS,etc.). The COL monitor circuitry 180 produces a direct shutdown indication (DIRECT SHUTDOWN) responsive to operations of the transistors 315, 320 exceeding safe operating conditions.

[0087] The V-I circuitry 705 receives the output supply voltage (PVDD) as the source voltage ofthe transistor 315. The V-I circuitry7705 produces a current proportional to the output supply voltage (PVDD). Similarly, the V-I circuitry 730 receives the output signal (OUTM) of the amplifier circuitry 140 as the source voltage of the transistor 320. The V-I circuitry 730 converts the drain-to-source voltage of the transistor 320 (VDS_M2) to a current (I(VDS_M2)). The combination circuitry 710 subtracts the current (I(VDS_M2)) from the V-I circuitry7730 from the current from the V-I circuitry7705. The combination circuitry 710 produces a current (I(VDS Ml)) corresponding to the drain-to-source voltage of the transistor 320 (VDS M1).

[0088] The COL fit circuitry 715 receives the current (I(VDS_M1)) from the combination circuitry7710. The COL fit circuitry 715 determines a COL drain current (COL ID Ml) that the transistor 315 may safely operate at using the current (I(VDS_M1)) and the COL curve 610 or the linear COL curve 620. In some examples, such a COL drain current (COL ID Ml) is referred to as a COL current (COL ID Ml). In example operations, the COL fit circuitry 715 provides the COL current (COL ID Ml) for the transistor 315 as a COL voltage (V(COL ID Ml))

[0089] Similarly, the COL fit circuitry 735 receives the current (I(VDS M2)) from the V-I circuitry 730. The COL fit circuitry 735 determines a COL drain current (COL ID M2) that the transistor 320 may safely operate at using the current (I(VDS_M2)) and the COL curve 610 or the linear COL curve 620. In some examples, such a COL drain current (COL ID M2) is referred to as a COL current (COL ID M2). In example operations, the COL fit circuitry 735 provides the COL current (COL_ID_M2) for the transistor 320 as a COL voltage (V(COL_ID_M2)). Advantageously, the COL fit circuitry7715, 735 provide the COL voltages (V(COL ID Ml), V(COL_ID_M2)) as representations of the COL currents of the transistors 315, 320.

[0090] The current sense circuitry 720 receives the gate-to-source voltage of the transistor 315 (VGS i), the output signal (OUTM) of the amplifier circuitry^ 140 as the source voltage (Vs) of the transistor 315, and the output supply voltage (PVDD) as the drain voltage (VD) of the transistor 315. The current sense circuitry 720 determines a current (ID_M1) through the transistor 315 for the given gate, source, and drain voltages (VG, VS, VD). In some examples, the current sense circuitry 720 includes a replica cunent path, which replicates the transistor315 to sense the current (ID_M1) without impacting the signal path. In example operations, the cunent sense circuitry 720 provides the current (ID_M1) of the transistor 315 as a voltage (V(ID_M1)).

[0091] Similarly, the current sense circuitry 740 receives the gate-to-source voltage of the transistor 320 (VGS 2), the output signal (OUTM) of the amplifier circuitry 140 as the drain voltage (VD) of the transistor 320, and the common potential (PGND) as the source voltage (Vs) of the transistor 320. The current sense circuitry 740 determines a current (ID_M2) through the transistor 320 for the gate, source, and drain voltages (VG, VS, VD). In some examples, the current sense circuitry' 740 includes a replica current path, which replicates the transistor 320 to sense the current (ID_M2) without impacting the signal path. In example operations, the current sense circuitry 740 provides the cunent (ID M2) of the transistor 320 as a voltage (V(ID_M2)). Advantageously, the current sense circuitry' 720, 740 provide the voltages (V(ID_M1), V(ID_M2)) as representations of the currents the transistors 315, 320 are conducting.

[0092] The comparator circuitry 725 compares the COL voltage (V(COL ID Ml)) from the COL fit circuitry 715 to the voltage (V(ID_M1)) from the current sense circuitry' 720. In example operations, the comparator circuitry' 725 determines if the current (ID_M1) of the transistor 315 is greater than the COL current (COL_ID_M1). In such example operations, the comparator circuitry 725 determines the transistor 315 is safely operating when the current (ID Ml) determined by the current sense circuitry 720 is less than the COL current (COL ID Ml) determined by the COL fit circuitry 715. In some examples, the comparator circuitry' 725 sets the output responsive to a determination that the transistor 315 is not safely operating. For example, the comparator circuitry 725 sets the output (e g., produces a logic level representing a logical one or logic high) if the voltage (V(ID_M1)) from the current sense circuitry 720 is greater than the COL voltage (V(COL ID Ml)) from the COL fit circuitry 715. Advantageously, the output of the comparator circuitry' 725 represents if the transistor 315 is operating within the COL curve 610 or the linear COL curve 620.

[0093] Similarly, the comparator circuitry’ 745 compares the COL voltage (V(COL_ID_M2)) from the COL fit circuitry 735 to the voltage (V(ID_M2)) from the current sense circuitry 740. In example operations, the comparator circuitry 745 determines if the current (ID_M2) of the transistor 320 is greater than the COL current (COL_ID_M2). In such example operations, the comparator circuitry 745 determines the transistor 320 is safely operating when the current (ID M2) determined by the current sense circuitry 740 is less than the COL current (COL ID M2) determined by the COL fit circuitry 735. In some examples,the comparator circuitry 745 sets the output responsive to a determination that the transistor 320 is not safely operating. For example, the comparator circuitry 745 sets the output if the voltage (V(ID_M2)) from the current sense circuitry 740 is greater than the COL voltage (V(COL_ID_M2)) from the COL fit circuitry 735. Advantageously, the output of the comparator circuitry 745 represents if the transistor 320 is operating within the COL curve 610 or the linear COL curve 620.

[0094] The logic device 750 receives the outputs of the comparator circuitry 725, 745, which represent a safe operating states of the transistors 315, 320. The logic device 750 logically combines the outputs of the comparator circuitry 725, 745. In the example of FIG. 7, the logic device 750 is an OR gate. In some embodiments, the logic device 750 may be an alternative gate or combination of logic components. In example operations, the logic device 750 sets an output responsive to either of the transistors 315, 320 not operating safely, such as beyond the COL curve 610.

[0095] The VGS detect circuitry' 755 receives the gate-to-source voltage of the transistors 315, 320 (VGS_1, VGS_2), the output signal (OUTM) of the amplifier circuitry 140, and the common potential (PGND). The VGS detect circuitry 755 determines if either of the transistors 315, 320 are operating in a linear mode. For example, the VGS detect circuitry 755 detects if the drain-to-source voltage (VDS_M1) of the transistor 315 is within the clamp region 630. In example operation, the VGS detect circuitry 755 sets an output responsive to a determination that the transistors 315, 320 are operating in a saturation mode.

[0096] The logic device 760 receives the output of the logic device 750 and the output of the VGS detect circuitry' 755. The logic device 760 logically combines the outputs of the logic device 750 and the VGS detect circuitry 755. In the example of FIG. 7, the logic device 760 is an AND gate. In some embodiments, the logic device 760 may be an alternative gate or combination of logic components. In example operations, the logic device 760 sets an output responsive to the transistors 315, 320 not operating safely in saturation mode, such as beyond the COL cun e 610 and the clamp region 630.

[0097] The deglitch circuitry’ 765 receives the output of the logic device 760. The deglitch circuitry 765 filters changes in the output of the logic device 760 shorter than a reference duration. In example operations, the deglitch circuitry 765 reduces a likelihood of errors impacting the timer circuitry' 770.

[0098] The timer circuitry' 770 receives the output of the deglitch circuitry 765. If the transistors 315, 320 are not safely operating in saturation mode, the timer circuitry 770 determines a duration that the transistors 315, 320 are not safely operating. The timer circuitry770 produces the direct shutdown indication (DIRECT_SHUTDOWN) responsive to either of the transistors 315, 320 not safely operating in saturation mode beyond a threshold time or duration. In some examples, the threshold time or duration is set based on the energy (Q) of the transistors 315, 320, which is proportional to the drain-to-source voltage and current. For example, the threshold time represents the energy consumed by the transistors 315, 320 can produce excessive temperatures. Advantageously, the timer circuitry’ 770 allows the transistors 315, 320 to briefly operate beyond the COL curve 610 or the linear COL curve 620 without generating produces the direct shutdown indication (DIRECT SHUTDOWN). Advantageously, the COL monitor circuitry 180 produces the direct shutdown indication (DIRECT_SHUTDOWN) responsive to either of the transistors 315, 320 operating beyond the COL curve 610 or the linear COL curve 620.

[0099] FIG. 8 is a flowchart of embodiment method 800, according to an embodiment of the present description. Method 800 may be performed using an example implementation of the COL monitor circuitry 180 of FIGs. 4 and 7 or more generally the load diagnostic circuitry’ 175 of FIGs. 3 and 4.

[0100] Method 800 begins at Block 805 at which the VGS detect circuitry 755 determines if the transistor is in linear operation. In example operations of the multi-class modulation circuitry’ 110, the amplifier circuitry’ 140 has a relatively large gain, which saturates the output signal (OUTM) of the amplifier circuitry 140 for a relatively large range of input signals.

[0101] In some examples, if the output signal (OUTM) of the amplifier circuitry 140 is saturated, the transistors 315, 320 operate in fixed states and have a relatively low likelihood of forming shorts from excessive currents. In such example operations, the amplifier circuitry’ 140 can rely on overcurrent protections, such as monitoring the current to the load (e.g., the speaker 160 or line out 170) to accurately sense safe operating conditions. Such linear operations of the transistors 315, 320 are represented by the clamp region 630. If the VGS detect circuitry’ 755 determines that the transistor is in linear operation (e.g., Block 805 returns a result of YES), control proceeds to return to Block 805.

[0102] If the V GS detect circuitry 755 determines that the transistor is not in linear operation (e.g.. Block 805 returns a result of NO), the V-I circuitry 705, 730 converts voltages of the transistor to currents. (Block 810). In example operations, the V-I circuitry 705, 730 convert the source voltages of the transistor 315, 320 to currents. In some examples, the V-I circuitry’ 730 represents the drain-to-source voltage (VDS_M2) of the transistor 320 as a current (I(VDS M2)). In such examples, the combination circuitry 710 represents the drain-to-sourcevoltage (VDS_M1) of the transistor 315 as a current (I(VDS_M1)) using the current (I(VDS_M2)) from the V-I circuitry 730 and the current from the V-I circuitry 705.

[0103] The COL fit circuitry 715, 735 determines a COL current of the transistor using the currents. (Block 815). In example operations, the COL fit circuitry 715, 735 determine COL currents (COL_ID_M1, COL_ID_M2) of the transistors 315, 320 using the currents (I(VDS_M1), I(VDS_M2)) from the combination circuitry 710 and the V-I circuitry 730. In such example operations, the COL fit circuitry 715, 735 use the COL curve 610 or the linear COL curve 620 to determine the COL currents (COL ID Ml , COL ID M2) of the transistors 315, 320. In some examples, the COL fit circuitry 715, 735 represents the COL currents (COL ID Ml, COL ID M2) of the transistors 315, 320 as COL voltages (V(COL ID Ml), V(COL ID M2)).

[0104] The current sense circuitry 720, 740 determines the current being conducted by the transistor. (Block 820). In example operations, the current sense circuitry' 720, 740 determine the drain currents (ID_M1, ID_M2) of the transistors 315, 320 based on the gate, source, and drain voltages (VG. VS, VD). In some examples, the current sense circuitry’ 720, 740 represents the drain currents (ID M1, ID_M2) of the transistors 315, 320 as voltages (V(ID_M1), V(ID_M2)).

[0105] The comparator circuitry' 725, 745 determines if the transistor is conducting current greater than the COL current. (Block 825). In example operations, the comparator circuitry 725, 745 compares the voltages (V(COL ID Ml), V(COL ID M2)) from the COL fit circuitry 715, 735 to the voltages (V(ID_M1), V(ID_M2)). In such example operations, the comparator circuitry' 725745 determines if either of the currents (ID_M1, ID_M2) through the transistors 315, 320 are greater than the COL currents (COL ID Ml, COL ID M2). Advantageously, the output of the comparator circuitry 715, 735 represents whether the transistors 315, 320 are operating within the COL curve 610 or the linear COL curve 620. If the comparator circuitry' 725, 745 -determines that the transistor is not conducting a current greater than the COL current (e.g., Block 825 returns a result of NO), control proceeds to return to Block 805. Advantageously, the transistors 315, 320 can continue to operate at currents below the COL curve 610.

[0106] If the comparator circuitry' 725, 745 determines that the transistor is conducting a current greater than the COL current (e.g., Block 825 returns a result of YES), the shutdow n circuitry 430 shuts down the transistor. (Block 830). In example operations, the timer circuitry 770 produces the direct shutdown indication (DIRECT SHUTDOWN) responsive to the logic device 760 indicating that either of the transistors 315, 320 are not operating safely in saturationmode. In some examples, the timer circuitry 770 waits to produce the direct shutdown indication (DIRECT SHUTDOWN) until either of the transistors 315, 320 continue to not safely operate for a time greater than a threshold. In such examples, the timer circuitry 770 waits for the energy consumption of the transistors 315, 320 to become excessive before generating the direct shutdown indication (DIRECT SHUTDOWN). For example, the threshold of the timer circuitry 770 corresponds to a time needed for the energy (Q) of the transistors 315, 320 to become excessive. The shutdown circuitry 430 disables the transistors 315, 320 or more generally the amplifier circuitry 140 responsive to the direct shutdown indication (DIRECT SHUTDOWN).

[0107] Control proceeds to End. Example methods are described with reference to the flowchart illustrated in FIG. 8. However, many other methods of implementing the COL monitor circuitry 180 of FIGs. 4 and 7 or more generally the load diagnostic circuitry 175 of FIGs. 3 and 4 may also be used in this description. For example, the order of execution of the blocks may be changed, or some of the blocks described may be changed, eliminated, or combined. Similarly, additional operations may be included in the manufacturing process before, in between, or after the blocks shown in the illustrated examples.

[0108] FIG. 9 is a timing diagram 900 of example operations of the amplifier circuitry 140 of FIGs. 1, 2, and 3 and the transistors 315, 320 without the load diagnostic circuitry7175 of FIGs. 3 and 4, according to an embodiment of the present description. In the example of FIG.9, the timing diagram 900 illustrates an example amplifier output 910, an example safe operating region 920, and an example unsupported output 930.

[0109] The amplifier output 910 represents the output signal (OUTM) of the amplifier circuitry 140. Prior to a first time 940 (Ts o), the amplifier circuitry 140 saturates the amplifier output 910 to the output power supply (PVDD). During such time, the transistors 315, 320 operate in a linear mode. Between the first time 940 and a second time 950 (Ts N), the amplifier output 910 transitions from the output power supply (PVDD) to the common potential (PGND). During such time, the transistors 315, 320 operate in saturation mode as the amplifier output 910 changes. In saturation mode, the currents of the transistors 315, 320 may produce a short across the transistor 315 to the output power supply (PVDD) or across the transistor 320 to the common potential (PGND). Advantageously, the COL monitor circuitry 180 detects the shorts across either of the transistors 315, 320 by comparing the COL currents to the sensed currents. Also, non-resistive loads, such as a subwoofer, may produce excessive currents through the transistors 315. 320. Advantageously, the COL monitor circuitry 180 detects excess currents from non-resistive loads by comparing the COL currents to sensed currents.

[0110] The safe operating region 920 represents a safe drain-to-source voltage (VDS) of the transistors 315. 320 during the operations of the amplifier circuitry 140. In example operations, the transistors 315, 320 are safely operating at drain-to-source voltages less than the safe operating region 920.[OHl] The unsupported output 930 represents the current (Id) of the transistors 315, 320 if the speaker 160 is replaced with an unsupported inductive load, such as a subwoofer, and the load diagnostic circuitry 175 is not active. In the example of FIG. 9, the unsupported output 930 represents the current of the transistors 315, 320 in the voltage domain for illustrative purposes. At the time 940, the inductive operating region 930 exceeds the safe operating region 920 as the transistors 315, 320 unsuccessfully attempt to drive the unsupported inductive load. After the time 940 and until the inductive operating region 930 falls below the safe operating region 920, the transistors 315, 320 generate excessive heat. During such example operations, the transistors 315, 320 risk damage from the excessive heat or thermal runaway conditions. Advantageously, as described herein, the COL monitor circuitry7180 detects the excursion of the drain-to-source voltage (VDS) of the transistors 315, 320 from the safe operating region 920 using the COL curves 610. 620.

[0112] FIG. 10 is an example timing diagram 1000 of example operations of the transistors 315, 320 without the load diagnostic circuitry 175, according to an embodiment of the present description. In the example of FIG. 10, the timing diagram 1000 illustrates temperatures of the transistors 315, 320 during operations beyond the safe operating region 920. At the first time 1010 (Ts M), the transistors 315, 320 begin at a safe operating temperature, which is considered a normal junction temperature. However, between the time 1010 and a second time 1020 (Ts i) the transistors 315, 320 begin operating beyond the safe operating region 920. During such times, such as between the times 1020 and 1030, the temperatures of the transistors 315, 320 exponentially increase. In some examples, if the temperatures of the transistors 315, 320 exceed an over temperature threshold, continuing operation of the transistors 315, 320 may lead to thermal runaway. In the example of FIG. 10, the temperatures at the time 950 (Ts N) may permanently damage the transistors 315, 320.

[0113] FIG. 11 is a timing diagram 1100 of example temperatures 1110 of the transistors 315, 320, according to an embodiment of the present description. In the example of FIG. 11, the timing diagram 1100 illustrates the temperatures 1110. The temperatures 1110 represent the increase in temperature of the transistors 315, 320 during continued operations beyond the COL curves 610. 620 or more generally the safe operating region 920. In the example of FIG.11, the temperatures 1110 continue to increase as the transistors 315, 320 continue to operateoutside of the COL curve 610, 620. In some examples, such as in FIG. 9, by the time 950, the temperature of the transistors 315. 320 may have exceeded the over temperature threshold. In such examples, the excess temperature can damage the transistors 315, 320.

[0114] FIG. 12 is a block diagram of an example integrated circuit (IC) 1200, according to an embodiment of the present description. In the example of FIG. 12, the IC 1200 includes a first channel 1205 (CHI), a second channel 1210 (CH2), a third channel 1215 (CH3), and a fourth channel 1220 (CH4). In the example of FIG. 12, the IC 1200 represents a placement of transistors, such as the transistors 315, 320, in a device package. The IC 1200 of FIG. 12 includes four instances of the multi-class modulation circuitry 110. The respective instances of the multi-class modulation circuitry 110 correspond to the channels 1205. 1210, 1215, 1220. Alternatively, the IC 1200 may include any number of instances of the multi-class modulation circuitry 110.

[0115] The channel 1205 (CHI) represents a first instance of the multi-class modulation circuitry7110 on the IC 1200. The example channel 1205 of FIG. 12 includes the transistors 315, 320, an example third transistor 1225, and a fourth example transistor 1230. The transistors 315, 320 correspond to the amplifier circuitry 140, which operates as a class AB amplifier. The transistors 1225, 1230 correspond to the amplifier circuitry7130, which operates as a class D amplifier. In example operations, the transistors 315, 320 consume more power implementing the linear operations of a class AB amplifier in comparison to the power consumption of the transistors 1225, 1230. As such, the temperatures of the transistors 315, 320 increase faster than temperatures of the transistors 1225, 1230.

[0116] The channel 1210 (CH2) represents a second instance of the multi-class modulation circuitry 110 on the IC 1200. The example channel 1210 of FIG. 12 includes a first example transistor 1235, a second example transistor 1240, a third example transistor 1245, and a fourth example transistor 1250. The transistors 1235, 1240 correspond to the amplifier circuitry 130, which operates as a class D amplifier. The transistors 1245, 1250 correspond to the amplifier circuitry7140, which operates as a class AB amplifier. In example operations, the transistors 1245, 1250 consume more power implementing the linear operations of a class AB amplifier in comparison to the power consumption of the transistors 1235. 1240. As such, the temperatures of the transistors 1245, 1250 increase faster than temperatures of the transistors 1235, 1240.

[0117] The channel 1215 (CH3) represents a second instance of the multi-class modulation circuitry 110 on the IC 1200. The example channel 1215 of FIG. 12 includes a first example transistor 1255, a second example transistor 1260, a third example transistor 1265, and a fourthexample transistor 1270. The transistors 1255. 1260 correspond to the amplifier circuitry 140, which operates as a class AB amplifier. The transistors 1265, 1270 correspond to the amplifier circuitry 130, which operates as a class D amplifier. In example operations, the transistors 1255, 1260 consume more power implementing the linear operations of a class AB amplifier in comparison to the power consumption of the transistors 1265, 1270. As such, the temperatures of the transistors 1255, 1260 increase faster than temperatures of the transistors 1265, 1270.

[0118] The channel 1220 (CH4) represents a second instance of the multi-class modulation circuitry 110 on the IC 1200. The example channel 1220 of FIG. 12 includes a first example transistor 1275, a second example transistor 1280, a third example transistor 1285, and a fourth example transistor 1290. The transistors 1275, 1280 correspond to the amplifier circuitry 130, which operates as a class D amplifier. The transistors 1285, 1290 correspond to the amplifier circuitry 140, which operates as a class AB amplifier. In example operations, the transistors 1285, 1290 consume more power implementing the linear operations of a class AB amplifier in comparison to the power consumption of the transistors 1275. 1280. As such, the temperatures of the transistors 1285, 1290 increase faster than temperatures of the transistors 1275, 1280. In some examples, the transistors 315, 320, 1245, 1250, 1255, 1260, 1285, 1290, which correspond to the class AB amplifiers, are positioned at the comers of the IC 1200 to decrease temperature across the IC 1200.

[0119] In the example of FIG. 12, the IC 1200 also includes example temperature sensors 1295 A, 1295B, 1295C, 1295D. The temperature sensors 1295 A, 1295B, 1295C, 1295D illustrate an example placement of respective instances of the temperature sensor 330 of FIG.3. The example placement of the temperature sensors 1295A, 1295B, 1295C, 1295D in FIG.12 are between transistors that implement class AB amplifiers. For example, the temperature sensor 1295A is placed in proximity to the transistors 315, 320, which implement the amplifier circuitry 140. Advantageously, such transistors are likely to exceed the overtemperature threshold before transistors that implement the class D amplifiers. Advantageously, placing the temperature sensors 1295A, 1295B, 1295C, 1295D in relation to the transistors 315, 320, 1245, 1250, 1255, 1260, 1285, 1290, which correspond to the class AB amplifiers, reduces the response time of the temperature monitor circuitry 420. Advantageously, decreasing the response time of the temperature monitor circuitry 420 increases the likelihood of preventing thermal runaway. Advantageously, positioning the temperature sensors 1295 A, 1295B, 1295C, 1295D in proximity to components that are more likely to heat up increases a response time of the temperature monitor circuitry 420.

[0120] FIG. 13 is a block diagram of example load diagnostic circuitry 1300, which is another example implementation of the load diagnostic circuitry 175 of FIG. 3 to safely operate the transistor 315, 320 of FIG. 3, according to an embodiment of the present description.

[0121] In some embodiments, load diagnostic circuitry 1300 may be implemented using a processor or controller coupled to a memory and configured to execute instructions from such memory. Some embodiments may be implemented or include a central processor unit (CPU), a field programmable gate array (FPGA), a hardware accelerator, and / or a state machine. In some embodiments, load diagnostic circuitry 1300 is implemented with synthesized logic. In some embodiments, load diagnostic circuitry 1300 is implemented in hardware only. In some embodiments, load diagnostic circuitry 1300 is configurable via registers. Other implementations may also be possible.

[0122] In the example of FIG. 13, the load diagnostic circuitry 1300 includes the temperature monitor circuitry 420 of FIG. 4, the shutdown circuitry 430 of FIG. 4, and COL monitor circuitry71310.

[0123] The COL monitor circuitry71310 receives the gate, source, and drain voltages (VG, Vs, VD) of the transistors 315, 320. The COL monitor circuitry 1310 determines the current flowing through the transistors 315, 320 using the voltages of the transistors 315, 320. The COL monitor circuitry71310 determines a COL current. The COL current is a threshold current corresponding to conditions that lead to thermal runaway.

[0124] Unlike in the example of FIG. 4. the COL monitor circuitry 180 produces a dynamic overtemperature threshold (DYN_THRESH) based on the operations of the transistors 315, 320. For example, the COL monitor circuitry 1310 produces a first overtemperature threshold responsive to either of the transistors 315, 320 exceeding a first level (LVL1) of safe operating conditions and a second overtemperature threshold responsive to either of the transistors 315, 320 exceeding a second level (LVL2) of safe operating conditions. In such examples, the COL monitor circuitry 1310 sets the second overtemperature threshold lower than the first overtemperature threshold to decrease the response time of the temperature sensor 330. Advantageously, the COL monitor circuitry 180 can further reduce the response time of the temperature monitor circuitry 420 by dynamically reducing the overtemperature threshold using a plurality of COL curves representing different operating levels.

[0125] Examples of the COL monitor circuitry 1310 are further illustrated and described in connection with FIGs. 14, 15, 16, 17, and 18. In some examples, the COL monitor circuitry 1310 is instantiated by ASIC or programmable circuitry executing COL monitor instructions to perform operations such as those represented by the flowchart of FIGs. 19A and 19B.

[0126] FIG. 14 is a block diagram of an example of the COL monitor circuitry 1310 of FIG.13, which is another example of the COL monitor circuitry 180 of FIGs. 4 and 7, according to an embodiment of the present description. In the example of FIG. 14, the COL monitor circuitry 1310 includes first detection circuitry 1405 and second detection circuitry 1410.

[0127] The detection circuitry 1405 receives the gate, source, and drain voltages (VG, VS, VD) of the transistor 315 and the current (ID_M2) of the transistor 320. The detection circuitry 1405 produces the dynamic threshold (DYN THRESH) based on a comparison of the current through the transistor 315 to a plurality of COL currents. The example detection circuitry 1405 of FIG. 14 includes example COL boundary circuitry 1415, example current sense circuitry 1420, example common mode circuitry 1425, example level divider circuitry 1430, and example level monitor circuitry 1435. In some examples, the detection circuitry 1405 is referred to as high-side detection circuitry', which monitors a high-side transistor, such as the transistor 315. An example of the detection circuitry 1405 is further illustrated and described in connection with FIG. 15.

[0128] The detection circuitry 1410 receives the gate, source, and drain voltages (VG, VS, VD) of the transistor 320. The detection circuitry' 1410 of FIG. 14 includes COL boundary circuitry 1440, current sense circuitry 1445, common mode circuitry 1450, level divider circuitry' 1455, and level monitor circuitry' 1460. In some examples, the detection circuitry' 1410 is referred to as low-side detection circuitry, which monitors a low-side transistor, such as the transistor 320. An example of the detection circuitry 1410 is further illustrated and described in connection with FIG. 1 .

[0129] The COL boundary' circuitry' 1415 converts the drain voltage (VD) of the transistor 315 to a current and subtracts the current (ID_M2) of the transistor 320 from the current sense circuitry 1445. In some examples, such as FIG. 3, the drain voltage of the transistor 315 is the output supply voltage (PVDD). Similar to the V-I circuitry 705 and the combination circuitry 710, the COL boundary' circuitry 1415 produces an output representing the drain-to-source voltage (VDS) of the transistor 315. An example of the COL boundary circuitry 1415 is further illustrated and described in connection with FIG. 15.

[0130] Similarly, the COL boundary circuitry' 1440 converts the drain voltage (VD) of the transistor 320. In some examples, such as FIG. 3, the drain voltage of the transistor 320 is the output signal (OUTM) of the amplifier circuitry 140. Similar to the V-I circuitry' 730, the COL boundary circuitry 1440 produces an output representing the drain-to-source voltage (VDS) of the transistor 320. An example of the COL boundary circuitry 1440 is further illustrated and described in connection with FIG. 16.

[0131] The current sense circuitry 1420 receives the gate-to-source voltage of the transistor 315 (VGS i), the output signal (OUTM) of the amplifier circuitry 140 as the source voltage (Vs) of the transistor 315, and the output supply voltage (PVDD) as the drain voltage (VD) of the transistor 315. The current sense circuitry 1420 determines a current (ID_M1) flowing through the transistor 315 for the given gate, source, and drain voltages (VG, VS, VD). In some examples, the current sense circuitry 1420 includes a replica current path, which replicates the transistor 315 to sense the current (ID Ml) without impacting the signal path. In example operations, the current sense circuitry 1420 provides the current (ID_M1) of the transistor 315 as a voltage (V(ID_M1)). The current sense circuitry 1420 is an example of the current sense circuitry 720.

[0132] Similarly, the current sense circuitry 1445 receives the gate-to-source voltage of the transistor 320 (VGS 2), the output signal (OUTM) of the amplifier circuitry 140 as the drain voltage (VD) of the transistor 320, and the common potential (PGND) as the source voltage (Vs) of the transistor 320. The current sense circuitry 1445 determines a current (ID_M2) through the transistor 320 for the gate, source, and drain voltages (VG, VS, VD). In some examples, the current sense circuitry 1445 includes a replica current path, which replicates the transistor 320 to sense the current (ID_M2) without impacting the signal path. In example operations, the current sense circuitry 1445 provides the current (ID_M2) of the transistor 320 as a voltage (V(ID_M2)). The current sense circuitry 1445 is an example of the current sense circuitry 740. Advantageously, the current sense circuitry 1420, 1445 provide the voltages (V(ID_M1), V(ID_M2)) as representations of the currents being conducted by the transistors 315, 320.

[0133] The common mode circuitry 1425 receives the drain-to-source voltage (VDS_M1) of the transistor 315 from the COL boundary circuitry 1415 and the voltage (V(ID_M1)) from the current sense circuitry 1420. The common mode circuitry 1425 sets a common mode voltage of the voltages (VDS_M1, V(ID_M1)). In some examples, the common mode circuitry 1425 reduces the common mode voltage of the voltages (VDS_M1, V(ID_M1)). In other examples, the common mode circuitry 1425 sets the common mode voltage of the voltages (VDS_M1, V(ID_M1)). An example of the common mode circuitry’ 1425 is further illustrated and described in connection with FIG. 15.

[0134] Similarly, the common mode circuitry 1450 receives the drain-to-source voltage (VDS_M2) of the transistor 320 from the COL boundary circuitry 1440 and the voltage (V(ID M2)) from the current sense circuitry 1445. The common mode circuitry 1450 sets a common mode voltage of the voltages (VDS_M2, V(ID_M2)). In some examples, the commonmode circuitry 1450 reduces the common mode voltage of the voltages (VDS_M2, V(ID_M2)). In other examples, the common mode circuitry 1450 sets the common mode voltage of the voltages (VDS_M2, V(ID_M2)). An example of the common mode circuitry 1450 is further illustrated and described in connection with FIG. 16.

[0135] The level divider circuitry 1430 receives the common mode adjusted representations of the voltages (VDS_M1, V(ID_M1), which represent the drain-to-source voltage (VDS_M1) of the transistor 315 and the current (ID_M1) through the transistor 315. The level divider circuitry 1430 produces a plurality of COL voltages using the drain-to-source voltage (VDS_M1) of the transistor 315. In some examples, the level divider circuitry71430 uses one or more of the COL curves 610, 620 to produce the COL voltages based on the drain-to-source voltage (VDS Ml) of the transistor 315. The plurality of COL voltages respectively represent different safety conditions of the transistor 315.

[0136] In some examples, such as FIGs. 15 and 18, each of the plurality of COL voltages corresponds to a level. A first level (LVL1) represents a mild COL curve where a transistor can continue to safety operate past for a first duration. A second level (LVL2) represents a moderate COL curve where a transistor can operate beyond for a second duration, which is shorter than the first duration. A third level (LVL3) represents a severe COL curve where a transistor cannot operate safely beyond for more than a third duration, which is a relatively short interval in comparison to the first and second durations. In some examples, the first, second, and third durations are determined using the energy (Q) of the transistors 315, 320 for given drain-to-source voltages and currents. Examples of the different levels are further illustrated and described in connection with FIGs. 15, 16, 17, and 18. The level divider circuitry 1430 provides the COL voltages and a signal voltage (VSIG(ID_M1)) representing the current through the transistor 315 as a voltage to the level monitor circuitry 1435. An example of the level divider circuitry 1430 is further illustrated and described in connection with FIG. 15.

[0137] Similarly, the level divider circuitry 1455 receives the common mode adjusted representations of the voltages (VDS_M2, V(ID_M2), which represent the drain-to-source voltage (VDS_M2) of the transistor 320 and the current (ID_M2) through the transistor 320. The level divider circuitry 1455 produces a plurality of COL voltages using the drain-to-source voltage (VDS_M2) of the transistor 320. In some examples, the level divider circuitry 1455 uses one or more of the COL curves 610, 620 to produce the COL voltages based on the drain-to-source voltage (VDS_M2) of the transistor 320. The plurality of COL voltages respectively represent different safety conditions of the transistor 320. The level divider circuitry 1455 provides the COL voltages and a signal voltage (VSIG(ID MI)) representing the currentthrough the transistor 320 as a voltage to the level monitor circuitry' 1460. An example of the level divider circuitry 1455 is further illustrated and described in connection with FIG. 16.

[0138] The level monitor circuitry 1435 compares the determined COL voltage(s) to the signal voltage, which represents the drain-to-source voltage of the transistor 315. The level monitor circuitry 1435 determines if the transistor 315 is not safely operating at any of the levels represented by the COL voltages. The level monitor circuitry’ 1435 changes the overtemperature threshold of the temperature monitor circuitry 420 responsive to the current through the transistor 315 exceeding the current corresponding to the COL voltages for longer than a threshold time. In some examples, the level monitor circuitry' 1435 includes a different threshold time for each level. An example of the level monitor circuitry 1435 is further illustrated and described in connection with FIG. 17.

[0139] Similarly, the level monitor circuitry 1460 compares the determined COL voltage(s) to the signal voltage, which represents the drain-to-source voltage of the transistor 320. The level monitor circuitry 1460 determines if the transistor 320 is not safely operating at any of the levels represented by the COL voltages. The level monitor circuitry 1460 changes the overtemperature threshold of the temperature monitor circuitry 420 responsive to the current through the transistor 320 exceeding the current corresponding to the COL voltages for longer than a threshold time. In some examples, the level monitor circuitry' 1460 includes a different threshold time for each level. An example of the level monitor circuitry 1460 is further illustrated and described in connection with FIG. 17.

[0140] Advantageously, the level monitor circuitry 1460 adjusts the overtemperature threshold of the temperature monitor circuitry’ 420 based on the severity' of the COL curve. In some examples, the level monitor circuitry 1460 decreases the overtemperature threshold as the severity’ of the COL curve increases. In such examples, the temperature monitor circuitry 420 detects lower overtemperatures of the transistors 315, 320 in comparison to relatively higher overtemperature conditions. Advantageously, the temperature monitor circuitry’ 420 produces the temperature shutdown indication (TEMP_SHUTDOWN) faster for COL curves with higher severity, such as level 3. Example COL curves are further illustrated and described in connection with FIG. 18.

[0141] FIG. 15 is a schematic diagram of an example of the detection circuitry 1405 of FIG.14, according to an embodiment of the present description. In the example of FIG. 15, the detection circuitry 1405 includes the COL boundary circuitry 1415, the common mode circuitry 1425, and the level divider circuitry 1430. In some examples, such as in FIG. 14, thedetection circuitry 1405 also includes the level monitor circuitry 1435. An example of the level monitor circuitry 1435 is illustrated and described in connection with FIG. 17.

[0142] The COL boundary circuitry 1415 receives the output supply voltage (PVDD) as the drain voltage (VD) of the transistor 315 and the voltage (V(ID_M2)) representing the current of the transistor 320. The example COL boundary circuitry 1415 of FIG. 15 includes example divider circuitry 1505, example V-I circuitry 1510, a first example transistor 1515, a second example transistor 1520, athird example transistor 1525, a fourth example transistor 1530, and a fifth example transistor 1535. The COL boundary circuitry 1415 produces a high-side COL current (I_COL_HS) as a current representative of the drain-to-source voltage (VDS_M1) of the transistor 315.

[0143] In example operations, the divider circuitry 1505 divides the output supply voltage (PVDD) to produce a voltage between the local supply voltage (AVDD) and the local common potential (AVSS). In some examples, the divider circuitry 1505 decreases the output supply voltage (PVDD). In such examples, the divider circuitry 1505 allows the detection circuitry 1405 to use relatively lower voltage components. The V-I circuitry 1510 converts the divided output supply voltage to a current. The transistors 1515, 1520 form current mirror circuitry. The transistors 1515, 1520 mirror the current from the V-I circuitry 1510. Similarly, the transistors 1525, 1530 form current mirror circuitry. The transistors 1515, 1520 mirror the current from the transistors 1520, which is approximately equal to the current from the V-I circuitry 1510. The transistor 1535 sinks a current based on the voltage (V(ID M2)) representing the current of the transistor 320. The transistor 1535 subtracts the current from the transistor 1530. The COL boundary circuitry 1415 produces a high-side COL current (I_COL_HS) responsive to the difference between the currents of the transistors 1530, 1535.

[0144] The common mode circuitry 1425 receives the voltage (V(ID_M1)) representing the current of the transistor 315 and the high-side COL current (I COL HS) representing the drain-to-source voltage (VDS_M1) of the transistor 315. The example common mode circuitry 1425 of FIG. 15 includes a first example resistor 1540, a first example current source 1545, a second example resistor 1550, and a second example current source 1555. The common mode circuitry 1425 produces a high-side COL voltage (VCM(I_COL_HS)) using the high-side COL current (I_COL_HS). The common mode circuitry 1425 produces a voltage (VCM(ID_M1)) using the voltage (V(ID_M1)).

[0145] In example operations, the current source circuitry 1545 sinks a trim current. The resistor 1540 produces the high-side COL voltage (VCM(I COL HS)) based on the difference between the high-side COL current (I COL HS) from the COL boundary circuitry 1415 andthe trim current from the current source circuitry' 1545. In some examples, the trim current of the current source circuitry 1545 is set to offset the high-side COL current (I COL HS) for common mode voltages. In such examples, sinking the trim current reduces the high-side COL voltage (VCM(I COL HS)) by a voltage approximately equal to the trim current times the resistance of the resistor 1540. Advantageously, the common mode circuitry' 1425 accounts for common mode shifts of the detection circuitry 1405.

[0146] In such example operations, the voltage (V(ID_M1)) controls the current source circuitry 1555. The current source circuitry’ 1555 sinks a current proportional to the current (ID_M1) through the transistor 315. The resistor 1550 produces the voltage (VCM(ID_M1)) responsive to the current source circuitry' 1555 sinking current. In some examples, the voltage (VCM(ID MI)) is approximately equal to the local supply voltage (AVDD) minus the voltage drop across the resistor 1550. In such examples, the voltage drop across the resistor 1550 is approximately equal to the resistance of the resistor 1550 times the current of the current source circuitry' 1555. Advantageously, the common mode circuitry 1425 produces the high-side COL voltage (VCM(I_COL_HS)) and the voltage (VCM(ID_M1)) in reference to the local supply voltage (AVDD).

[0147] The level divider circuitry 1430 receives the high-side COL voltage (VCM(I_COL_HS)) representing the drain-to-source voltage (VDS) of the transistor 315 and the voltage (VCM(ID_M1)) representing the current (ID_M1) flowing through the transistor 315. The example level divider circuitry 1430 of FIG. 15 includes a first example transistor 1560, a first example resistor 1565, a second example resistor 1570, a third example resistor 1575, a first example current source 1580, a second example transistor 1585, and a second example current source 1590. The level divider circuitry' 1430 produces a first COL voltage (VLVLI(COL ID MI)), a second COL voltage (VLVL2(COL_ID_M1)), and a third COL voltage (VLVL?(COL_ID_M1)) using the voltage (VCM(ID_M1)). The level divider circuitry 1430 produces a transistor signal voltage (VSIG(ID_M1)) using the high-side COL voltage (VCM(I COL HS)).

[0148] In example operations, the transistor 1560 supplies a current based on the voltage (VCM(ID MI)) from the common mode circuitry 1425. The current of the transistor 1560 represents the current flowing through the transistor 315. The resistors 1565, 1570, 1575 form a resistor divider (also referred to as a resistor ladder). The resistors 1565, 1570, 1575 produce the COL voltages (VLVLI(COL ID MI), VLVL2(COL_ID_M1). VLVL3(COL_ID_M1)) responsive to the current from the transistor 1560. In some examples, the resistances of the resistors 1565, 1570, 1575 form three COL levels representing different severities of operatingconditions. For example, the resistor 1565 produces a first level (LVL1) representing a mild COL curve responsive to having a resistance of one-thousand ohms. In such examples, the resistor 1570 produces a second level (LVL2) representing a moderate COL curve responsive to having a resistance of five-thousand ohms. Also, in such examples, the resistor 1575 produces a third level (LVL3) representing a severe COL curve responsive to having a resistance of ten-thousand ohms. In the example of FIG. 15, the detection circuitry 1405 implements linear COL curves, such as the linear COL curve 620. Examples of the COL curves at different severity levels are further illustrated and described in connection with FIG. 18.

[0149] In such example operations, the current source circuitry 1580 sinks a trim current from the resistor divider of the resistors 1565, 1570. 1575. In some examples, the trim current of the current source circuitry 1580 allows designers to adjust the offset of COL curves, such as the COL curves 610, 620. In such examples, the current source circuitry 1580 can be set to account for variations in the detection circuitry 1405.

[0150] In example operations, the transistor 1585 supplies a current based on the high-side COL voltage (VCM(I_COL_HS)) from the common mode circuitry 1425. The transistor 1585 generates the transistor signal voltage (VSIG(ID_M1)) based on the high-side COL voltage (VCM(I COL HS)) from the common mode circuitry 1425 and the local supply voltage (AVDD). In such example operations, similar to the current source circuitry 1580, the current source circuitry 1590 sinks a trim current from the transistor 1585. In some examples, the trim current of the current source circuitry 1590 allows designers to account for variations in the detection circuitry 1405. Advantageously, the transistor 1585 produces the transistor signal voltage (VSIG(ID_M1)) as a representation of the drain-to-source voltage of the transistor 315.

[0151] In the example of FIG. 15, the transistors 1515, 1520, 1535, 1560, 1585 aren-channel MOSFETs. Alternatively, the transistors 1515, 1520, 1535. 1560, 1585 may be n-channel FETs, n-channel IGBTs, n-channel JFETs, NPN BJTs or, with slight modifications, p-type equivalent devices. In the example of FIG. 15, the transistors 1525, 1530 are p-channel MOSFETs. Alternatively, the transistors 1525, 1530 may be p-channel FETs, p-channel IGBTs. p-channel JFETs, PNP BJTs, or, with slight modifications, N-type equivalent devices. The transistors 1515, 1520, 1525, 1530, 1535, 1560, 1585 may be depletion mode devices, drain-extended devices, enhancement mode devices, natural transistors or other type of device structure transistors. Furthermore, the transistors 1515, 1520, 1525, 1530, 1535, 1560, 1585 may be implemented in / over a silicon substrate (Si), a silicon carbide substrate (SiC), a gallium nitride substrate (GaN) or a gallium arsenide substrate (GaAs).

[0152] FIG. 16 is a schematic diagram of an example of the detection circuitry 1410 of FIG.14, according to an embodiment of the present description. In the example of FIG. 16, the detection circuitry 1410 includes the COL boundary circuitry 1440, the common mode circuitry 1450, and the level divider circuitry 1455. In some examples, such as in FIG. 14, the detection circuitry71410 also includes the level monitor circuitry 1460. An example of the level monitor circuitry 1460 is illustrated and described in connection with FIG. 17.

[0153] The COL boundary circuitry 1440 receives the output signal (OUTM) of the amplifier circuitry 140 as the drain voltage (VD) of the transistor 320. The example COL boundary circuitry 1440 of FIG. 16 includes example divider circuitry71605, example V-I circuitry 1610, a first example transistor 1615, and a second example transistor 1620. The COL boundary¬ circuitry 1440 produces a low-side COL current (I COL LS) as a current representative of the drain-to-source voltage (VDS_M2) of the transistor 320.

[0154] In example operations, the divider circuitry 1605 divides the output signal (OUTM) of the amplifier circuitry 140 to produce a voltage between the local supply voltage (AVDD) and the local common potential (AVSS). In some examples, the divider circuitry 1605 decreases the output signal (OUTM) of the amplifier circuitry 140. In such examples, the divider circuitry 1605 allows the detection circuitry' 1410 to use relatively lower voltage components. The V-I circuitry71610 converts the divided output voltage to a current. The transistors 1615, 1620 form current mirror circuitry. The transistors 1615, 1620 mirror the current from the V-I circuitry 1610. The transistor 1615 also provides the voltage (V(ID M2)) representing the current of the transistor 320 to the detection circuitry71405. The COL boundary7circuitry71440 produces the low-side COL current (I COL LS) responsive to the transistors 1615, 1620 mirroring the output of the V-I circuitry71610.

[0155] The common mode circuitry 1450 receives the voltage (V(ID_M2)) representing the current of the transistor 320 and the low-side COL current (I_COL_LS) representing the drain-to-source voltage (VDS_M2) of the transistor 320. The example common mode circuitry 1450 of FIG. 16 includes a first example resistor 1625, a first example current source 1630, a second example resistor 1635, and a second example current source 1640. The common mode circuitry 1450 produces a low-side COL voltage (VCM(I COL LS) using the high-side COL cunent (I_COL_HS). The common mode circuitry 1450 produces a voltage (VCM(ID_M2)) using the voltage (V(ID_M2)).

[0156] In example operations, the current source circuitry 1630 supplies a trim current. The resistor 1625 produces the low-side COL voltage (VCM(I COL LS)) based on the difference between the low-side COL current (I COL LS) from the COL boundary circuitry 1440 andthe trim current from the current source circuitry' 1630. In some examples, the trim current of the current source circuitry 1630 is set to offset the low-side COL current (I_COL_LS) for common mode voltages. In such examples, supplying the trim cunent increases the low-side COL voltage (VCM(I COL LS)) by a voltage approximately equal to the trim current times the resistance of the resistor 1625. Advantageously, the common mode circuitry' 1450 accounts for common mode shifts of the detection circuitry 1410.

[0157] In such example operations, the voltage (V(ID_M2)) controls the current source circuitry 1640. The current source circuitry 1640 supplies a current proportional to the current (ID_M2) through the transistor 320. The resistor 1635 produces the voltage (VCM(ID_M2)) responsive to the current source circuitry' 1640 supplying current. In some examples, the voltage (VCM(ID M2)) is approximately equal to the local common potential (AVSS) plus the voltage drop across the resistor 1635. In such examples, the voltage drop across the resistor 1635 is approximately equal to the resistance of the resistor 1635 times the current of the current source circuitry 1640. Advantageously, the common mode circuitry 1450 produces the low-side COL voltage (VCM(I COL LS)) and the voltage (VCM(ID_M2)) in reference to the local common potential (AVSS).

[0158] The level divider circuitry 1455 receives the low-side COL voltage (VCM(I_COL_LS)) representing the drain-to-source voltage (VDS) of the transistor 320 and the voltage (VCM(ID_M2)) representing the current (ID_M2) flowing through the transistor 320. The example level divider circuitry 1455 of FIG. 16 includes a first example transistor 1645, a first example resistor 1650, a second example resistor 1655, a third example resistor 1660, a first example current source 1665, a second example transistor 1670, and a second example current source 1675. The level divider circuitry' 1455 produces a first COL voltage (VLVLI(COL_ID_M2)), a second COL voltage (VLVL2(COL_ID_M2)), and a third COL voltage (VLVL?(COL_ID_M2)) using the low-side COL voltage (VCM(I_COL_LS)). The level divider circuitry 1455 produces a transistor signal voltage (VSIG(ID_M2)) using the voltage (VCM(ID_M2)).

[0159] In example operations, the transistor 1645 sinks a current based on the low-side COL voltage (VCM(I_COL_LS)) from the common mode circuitry 1450. The current of the transistor 1645 represents the drain-to-source voltage of the transistor 320. The resistors 1650, 1655, 1660 form a resistor divider (also referred to as a resistor ladder). The resistors 1650, 1655, 1660 produce the COL voltages (VLVLI(COL_ID_M2), VLVL2(COL_ID_M2), VLVI COL ID M2)) responsive to the current of the transistor 1645. In some examples, the resistances of the resistors 1650, 1655, 1660 are selected to form three COL levels representingdifferent severities of operating conditions. For example, the resistor 1650 produces a first level (LVL1) representing a mild COL curve responsive to having a resistance of one-thousand ohms. In such examples, the resistor 1655 produces a second level (LVL2) representing a moderate COL curve responsive to having a resistance of five-thousand ohms. Also in such examples, the resistor 1660 produces a third level (LVL3) representing a severe COL curve responsive to having a resistance of ten-thousand ohms. In the example of FIG. 16, the detection circuitry 1410 implements linear COL curves, such as the linear COL curve 620. Examples of the COL curves for different severity levels are further illustrated and described in connection with FIG. 18.

[0160] In such example operations, the current source circuitry 1665 supplies a trim current to the resistor divider of the resistors 1650, 1655, 1660. In some examples, the trim current of the cunent source circuitry 1665 allows designers to adjust the offset of COL curves, such as the COL curves 610, 620. In such examples, the current source circuitry 1665 can be set to account for variations in the detection circuitry 1410.

[0161] In example operations, the transistor 1670 sinks a current based on the voltage (VCM(ID_M2)) from the common mode circuitry 1450. The transistor 1670 generates the transistor signal voltage (VSIG(ID_M2)) based on the voltage (VCM(ID_M2)) from the common mode circuitry' 1450 and the local common potential (AVSS). In such example operations, similar to the current source circuitry 1665, the current source circuitry 1675 supplies a trim current to the transistor 1670. In some examples, the trim current of the current source circuitry 1675 allows designers to account for variations in the detection circuitry 1410. Advantageously, the transistor 1670 produces the transistor signal voltage (VSIG(ID_M2)) as a representation of the current flowing through the transistor 320.

[0162] In the example of FIG. 16. the transistors 1615, 1620 are n-channel MOSFETs. Alternatively, the transistors 1615, 1620 may be n-channel FETs, n-channel IGBTs, n-channel JFETs, NPN BJTs or, with slight modifications, p-type equivalent devices. In the example of FIG. 16, the transistors 1645, 1670 are p-channel MOSFETs. Alternatively, the transistors 1525, 1530 may be p-channel FETs, p-channel IGBTs, p-channel JFETs, PNP BJTs, or. with slight modifications, N-type equivalent devices. The transistors 1615, 1620, 1645, 1670 may be depletion mode devices, drain-extended devices, enhancement mode devices, natural transistors or other type of device structure transistors. Furthermore, the transistors 1615, 1620, 1645. 1670 may be implemented in / over a silicon substrate (Si), a silicon carbide substrate (SiC), a gallium nitride substrate (GaN) or a gallium arsenide substrate (GaAs).

[0163] FIG. 17 is a block diagram of example level monitor circuitry' 1700, which is an example of the level monitor circuitry 1435, 1460 of FIG. 14, according to an embodiment of the present description. In the example of FIG. 17, the level monitor circuitry 1700 includes a first switch circuitry 1705, a comparator 1710, deglitch circuitry 1715, second switch circuitry 1720, a first timer circuitry' 1725, a second timer circuitry' 1730, a third timer circuitry' 1735, and over temperature (OT) threshold circuitry 1740.

[0164] The level monitor circuitry 1700 receives the COL voltages (VLVLI(COL_ID_MX), VLVL2(COL_ID_MX), VLVLS(COL_ID_MX)) and the transistor signal voltage (VSIG(ID_MX)) from the level divider circuitry 1430, 1455. In some examples, such as the load diagnostic circuitry 1300 of FIG. 13, the level monitor circuitry 1700 produces the dynamic over temperature threshold (DYN THRESH) for the temperature monitor 420. In such examples, the level monitor circuitry' 1700 adjusts the over temperature threshold of the temperature monitor 420 based on a comparison of the COL voltages (COL voltages (VLVLI(COL ID MX), VLVL2(COL_ID_MX), VLVL3(COL_ID_MX)) to the transistor signal voltage (VSIG(ID_MX)). In other examples, such as in FIG. 21, the level monitor circuitry 1700 produces the dynamic over temperature threshold (DYN THRESH) and a direct shutdown indication (DIRECT SHUTDOWN). In such examples, the level monitor circuitry 1700 provides the direct shutdown indication (DIRECT SHUTDOWN) to the shutdown circuitry' 430. Advantageously, the level monitor circuitry 1700 can dynamically change the overtemperature threshold or disable the transistors 315, 320 using the COL voltages (VLVLI(COL ID MX), VLVL2(COL_ID_MX), VLVL3(COL_ID_MX)) and the transistor signal voltage (VSIG(ID MX)).

[0165] The switch circuitry' 1705 has a control input (also referred to as a control terminal) coupled to a clock signal (CLK). The clock signal periodically adjusts the state of the switch circuitry 1705. For example, during a first cycle of the clock signal (CLK), the switch circuitry 1705 provides the first COL voltage (VLVLI(COL_ID_MX)) to the comparator 1710. During a second cycle of the clock signal (CLK), the switch circuitry 1705 provides the second COL voltage (VLVL2(COL_ID_MX)) to the comparator 1710. During a third cycle of the clock signal (CLK), the switch circuitry 1705 provides the third COL voltage (VLVL3(COL_ID_MX)) to the comparator 1710. After the third cycle, the switch circuitry' 1705 returns to the first COL voltage (VLVLI(COL_ID_MX)). Alternatively, the level monitor circuitry 1700 may include alternative circuitry' to provide the COL voltages to the comparator 1710. For example, the level monitor circuitry 1700 may include a comparator for each of the COL voltages (Vi.vi.i(COL_ID_MX), VI VI2(COL_ID_MX), VI.VI.3(COL_ID_MX)).

[0166] The comparator 1710 compares the transistor signal voltage (VSIG(ID_MX)) to the respective one of the COL voltages (VLVLI(COL ID MX). VLVL2(COL_ID_MX), VLVL3(COL_ID_MX)) from the switch circuitry 1705. The comparator 1710 determines if the transistors 315, 320 are exceeding the COL curve corresponding to the provided COL voltage responsive to the comparison. The output of the comparator 1710 indicates if one of the transistors 315. 320 are operating beyond a COL curve.

[0167] The deglitch circuitry 1715 receives the output of the comparator 1710. The deglitch circuitry 1715 filters changes in the output of the comparator 1710 shorter than a reference duration. In example operations, the deglitch circuitry 1715 reduces a likelihood of errors impacting the timer circuitry 1725, 1730, 1735.

[0168] The switch circuitry 1720 has a control input coupled to the clock signal (CLK). Similar to the switch circuitry 1705, the clock signal (CLK) periodically adjusts the state of the switch circuitry 1720. For example, during the first cycle of the clock signal (CLK), the switch circuitry 1720 provides the output of the deglitch circuitry' 1715 to the timer circuitry' 1725. During the second cycle of the clock signal (CLK), the switch circuitry 1720 provides the output of the deghtch circuitry 1715 to the timer circuitry 1730. During the third cycle of the clock signal (CLK), the switch circuitry 1720 provides the output of the deglitch circuitry 1715 to the timer circuitry' 1735. After the third cycle, the switch circuitry' 1720 returns to the timer circuitry 1725. Alternatively, the level monitor circuitry 1700 may include alternative circuitry to provide the output of the deglitch circuitry’ 1715 to the timer circuitry 1725, 1730, 1735. For example, the level monitor circuitry' 1700 may include a comparator for each COL level (LVL1, LVL2, LVL3).

[0169] The timer circuitry 1725 receives the output of the deglitch circuitry 1715 when the comparator 1710 is comparing the first COL voltage (VLVLI(COL_ID_MX)) to the transistor signal voltage (VSIG(ID_MX)). In example operations, the timer circuitry 1725 starts a timer responsive to the transistor signal voltage (VSIG(ID_MX)) being greater than the first COL voltage (VL LI(COL_ID_MX)). The timer circuitry 1725 continues to let the timer run until the comparator 1710 determines that the transistor signal voltage (VSIG(ID_MX)) is greater than the first COL voltage (VLVLI(COL ID MX)). In such example operations, if the timer becomes greater than a first threshold time, the timer circuitry 1725 generates a level one COL indication (COL LVLl). The level one COL indication (COL LVLl) represents that the transistors 315, 320 continue to operate beyond the first level COL curve for longer than the first threshold time.

[0170] The timer circuitry 1730 receives the output of the deglitch circuitry 1715 when the comparator 1710 is comparing the second COL voltage (VLVL2(COL_ID_MX)) to the transistor signal voltage (VSIG(ID_MX)). In example operations, the timer circuitry 1730 starts a timer responsive to the transistor signal voltage (VSIG(ID_MX)) being greater than the second COL voltage (VLVL2(COL_ID_MX)). The timer circuitry 1730 continues to let the timer run until the comparator 1710 determines that the transistor signal voltage (VSIG(ID_MX)) is greater than the second COL voltage (VLVL2(COL_ID_MX)). In such example operations, if the timer becomes greater than a second threshold time, the timer circuitry 1730 generates a level two COL indication (COL LVL2). The level two COL indication (COL LVL2) represents that the transistors 315, 320 continue to operate beyond the second level COL curve for longer than the second threshold time.

[0171] The timer circuitry 1735 receives the output of the deglitch circuitry 1715 when the comparator 1710 is comparing the third COL voltage (VLVL3(COL_ID_MX)) to the transistor signal voltage (VSIG(ID_MX)). In example operations, the timer circuitry 1735 starts a timer responsive to the transistor signal voltage (VSIG(ID_MX)) being greater than the third COL voltage (VLVL?(COL_ID_MX)). The timer circuitry 1735 continues to let the timer run until the comparator 1710 determines that the transistor signal voltage (VSIG(ID_MX)) is greater than the third COL voltage (VLVL3(COL_ID_MX)). In such example operations, if the timer becomes greater than a third threshold time, the timer circuitry 1730 generates a level three COL indication (COL LVL3). The level three COL indication (COL LVL3) represents that the transistors 315, 320 continue to operate beyond the third level COL curve for longer than the third threshold time. In some examples, the timer circuitry 1735 produces the direct shutdown indication (DIRECT SHUTDOWN) responsive to the timer exceeding the third threshold time.

[0172] The OT threshold circuitry 1740 receives the COL indications (COL LVLl, COL LVL2, COL LVL3) from the timer circuitry 1725, 1730, 1735. The OT threshold circuitry71740 produces the dynamic over temperature threshold (DYN_THRESH) responsive to receiving any of the COL indications (COL LVLl, COL LVL2, COL LVL3). In some examples, the OT threshold circuitry’ 1740 adjusts the over temperature threshold of the temperature monitor circuitry 420 based on which of the COL indications (COL LVLl, COL LVL2, COL LVL3) are received. For example, the OT threshold circuitry' 1740 produces a first dynamic over temperature threshold responsive to receiving a COL indication from the timer circuitry 1725. The OT threshold circuitry 1740 produces a second dynamic over temperature threshold responsive to receiving a COL indication from the timer circuitry1730. The OT threshold circuitry 1740 produces a third dynamic over temperature threshold responsive to receiving a COL indication from the timer circuitry 1735. In such examples, the OT threshold circuitry 1740 sets the overtemperature threshold based on the level of the COL curve. For example, the third overtemperature threshold is lower to the second overtemperature threshold to have the temperature monitor circuitry 420 respond faster if the transistors 315, 320 are operating beyond the severe COL curve. Advantageously, the OT threshold circuitry 1740 adjusts the dynamic overtemperature threshold (DYN_THRESH) based on the severity of the COL violation.

[0173] FIG. 18 is a plot 1800 of example COL curves of the transistors 315, 320, according to an embodiment of the present description. In the example of FIG. 18, the plot 1800 illustrates a first COL curve 1810, a second COL curve 1820, a third COL curve 1830, a first linear COL curve 1840, a second linear COL curve 1850, a third linear COL curve 1860, and a clamp region 1870.

[0174] The COL curves 1810, 1820, 1830 are functions of a drain current (ID_MX) across a range of drain-to-source voltages (VDS_MX) for a given transistor. In some examples, the COL curves 1810, 1820, 1830 plot the drain-to-source voltage (VDS_MX) of a transistor in terms of current (I(VDS_MX)) and the drain current (ID_MX) across a range of the transistor in terms of voltage (V(ID_MX)). In such examples, the COL monitor circuitry 1310 determines the current (I(VDS_MX)) by converting the drain-to-source voltage (VDS_MX) of the transistor to a current. Similarly, the COL monitor circuitry 1310 determines the voltage (V(VDS_MX)) by generating a voltage proportional to the drain current (ID_MX). In example operations, the COL curves 1810, 1820, 183 O plot the drain current (ID_MX) for a given drain-to-source voltage (VDS_MX). Such a drain current (ID_MX) along the COL curves 1810, 1820, 1830 is referred to as the COL current. Alternatively, the COL curves 1810, 1820, 1830 may provide a COL voltage as the drain-to-source voltage (VDS_MX) for a given drain current (ID MX).

[0175] In some examples, such as in FIGs. 13, 14, 15, 16, and 17, the COL monitor circuitry 1310 uses a plurality of COL curves, such as the COL curves 1810, 1820, 1830. In such examples, each of the COL curves 1810, 1820, 1830 are referred to as a level. For example, the COL curve 1810 is a first level (LVL1), the COL curve 1820 is a second level (LVL2), and the COL curve 1830 is a third level (LVL3). In some such examples, the first level (LVL1) represents the least severe (also referred to as mild) conditions, the second level (LVL2) represents the second least severe (also referred to as moderate) conditions, and the third level (LVL3) represents the most severe (also referred to as extreme) conditions. In exampleoperations, the transistors 315, 320 can continue to operate safely in conditions below the COL curve 1810. However, the transistors 315, 320 are more prone to damage as the drain-to-source voltage or drain current of the transistors 315, 320 increase beyond the COL curve 1810.

[0176] In some examples, such as in FIG. 17, the COL monitor circuitry 1310 allows the transistors 315, 320 to operate between the COL curves 1810, 1820 for the first threshold time of the timer circuitry 1725. Similarly, the COL monitor circuitry 1310 allows the transistors 315, 320 to operate between the COL curves 1820, 1830 for the second threshold time of the timer circuitry 1730. In such examples, the COL monitor circuitry 1310 allows the transistors 315, 320 to operate beyond the COL curve 1830 for the third threshold time of the timer circuitry 1735.

[0177] The linear COL curves 1840. 1850, 1860 are linear approximations of the COL curves 1810, 1820, 1830. In some examples, implementing the curvature of the COL curves 1810, 1820, 1830 substantially increases the complexity of a device. In such examples, designers may implement the linear COL curves 1840, 1850, 1860 to approximate the COL curves 1840, 1850. 1860. Advantageously, the linear COL curves 1840. 1850, 1860 reduce the integration complexity of the COL monitor circuitry 1310.

[0178] The clamp region 1870 is a range of gate-to-source voltages (VGS_MX) where a transistor operates in a linear mode. In some examples, such as the amplifier circuitry’ 140, the transistors 315, 320 operate in linear mode when the output signal (OUTM) of the amplifier circuitry 140 is saturated. In such examples, as illustrated by the exponential increase in the COL curves 181 , 1820, 1830, the transistors 315, 320 are capable of safely operating with relatively large drain currents (ID_MX). Advantageously, the transistors 315, 320 are unlikely to experience positive thermal feedback across continuing operations in the clamp region 1870. Advantageously, the COL monitor circuitry 1310 may limit monitoring to saturation operations of the transistors 315, 320, such as a transition between saturated states.

[0179] FIGs. 19A and 19B illustrate a flowchart of embodiment method 1900, according to an embodiment of the present description. Method 199 may be performed by COL monitor circuitry 1310 of FIGs. 13 and 14 or more generally the load diagnostic circuitry’ 1300 of FIGs.3 and 13.

[0180] Method 1900 begin with Blocks 505, 510 of FIG. 5. Control proceeds to Block 1912.

[0181] If the temperature monitor circuitry’ 420 determines the temperature of the transistor is not greater than the overtemperature threshold (e g., Block 510 returns a result of NO), the COL boundary circuitry 1415, 1440 convert voltages of the transistor to current. (Block 1912). In example operations, the COL boundary circuitry 1415, 1440 generate the COL currents(I_COL_HS, I_COL_LS) based on the drain voltages of the transistor 315, 320. For example, the high-side COL current (I_COL_HS) represents the drain-to-source voltage (VDS) of the transistor 315 and the low-side COL cunent (I COL LS) represents the drain-to-source voltage (VDS) of the transistor 320.

[0182] The current sense circuitry 1420, 1445 determines current being conducted by the transistor. (Block 1916). In example operations, the current sense circuitry 1420, 1445 determine the drain currents (ID_M1, ID_M2) of the transistors 315, 320 based on the gate, source, and drain voltages (VG, VS, VD). In some examples, the current sense circuitry 1420, 1445 represents the drain currents (ID_M1, ID_M2) of the transistors 315, 320 as voltages (V(ID_M1), V(ID_M2))

[0183] The common mode circuitry 1425, 1450 sets a common mode voltage of the currents. (Block 1920). In example operations, the common mode circuitry 1425, 1450 use the resistors 1540, 1625 and the current source circuitry 1545, 1630 to adjust the common mode voltage of the high and low side COL currents (I COL HS, I COL LS). The common mode circuitry71425, 1450 produce the voltages (VCM(I_COL_HS), VCM(I_COL_LS)) in relation to one of the local power supply (AVDD) or the local common potential (AVSS). In such example operations, the common mode circuitry 1425, 1450 use the resistors 1550, 1635 and the current source circuitry71555, 1640 to produce the voltage (VCM(ID_M1), VCM(ID_M2)) in relation to one of the local power supply (PVDD) or the local common potential (AVSS).

[0184] The level divider circuitry 1430, 1455 determines a first continuous operating loss (COL) current of the transistor. (Block 1924). In example operations, the level divider circuitry 1430, 1455 use the respective one of the voltages (VCM(I_COL_HS), VCM(I_COL_LS)) to generate the first COL voltage (VLVLI(COL_ID_MX)). For example, the transistor 1560 supplies a current responsive to the voltage (VCM(I COL HS)). In such examples, the resistor 1565 produces the first COL voltage (VLVLI(COL_ID_M1)) using the current from the transistor 1560. Similarly, the resistor 1650 produces the first COL voltage (VLVLI(COL_ID_M2)) responsive to current of the transistor 1645, which is set by the voltage (VCM(I COL LS)). In such example operations, the first COL voltage (VLVLI(COL_ID_MX)) corresponds to the linear COL curve 1840. In some examples, the first COL voltage (VLVLI(COL_ID_M1)) represents the first level (LVL1), which is associated with the least severe operating state of the transistors 315, 320.

[0185] The level divider circuitry71430, 1455 determines a second COL current of the transistor using the currents. (Block 1928). In example operations, the level divider circuitry 1430, 1455 use the respective one of the voltages (VCM(I COL HS), VCM(I_COL_LS)) togenerate the second COL voltage (VLVL2(C0L_ID_MX)). For example, the transistor 1560 supplies a current responsive to the voltage (VCM(I COL HS)). In such examples, the resistor 1570 produces the second COL voltage (VLVL2(COL_ID_M1)) using the current from the transistor 1560. Similarly, the resistor 1655 produces the second COL voltage (VLVL2(COL_ID_M2)) responsive to current of the transistor 1645, which is set by the voltage (VCM(I COL LS)). In such example operations, the second COL voltage (VLVL2(COL_ID_MX)) corresponds to the linear COL curve 1850. In some examples, the second COL voltage (VLVL2(COL_ID_M1)) represents the second level (LVL2), which is associated with a moderately severe operating state of the transistors 315, 320.

[0186] The level divider circuitry 1430, 1455 determines a third COL current of the transistor using the currents. (Block 1932). In example operations, the level divider circuitry 1430, 1455 use the respective one of the voltages (VCM(I_COL_HS), VCM(I_COL_LS)) to generate the third COL voltage (VLVL3(COL_ID_MX)). For example, the transistor 1560 supplies a current responsive to the voltage (VCM(I_COL_HS)). In such examples, the resistor 1575 produces the third COL voltage (VLVL3(COL_ID_M1)) using the current from the transistor 1560. Similarly, the resistor 1660 produces the third COL voltage (VLVL3(COL_ID_M2)) responsive to current of the transistor 1645, which is set by the voltage (VCM(I_COL_LS)). In such example operations, the third COL voltage (VLVL3(COL_ID_MX)) corresponds to the linear COL curve 1860. In some examples, the third COL voltage (VLVL3(COL_ID_M1)) represents the third level (LVL3), which is associated with the most severe operating state of the transistors 315, 320.

[0187] The level divider circuitry 1430, 1455 determines a signal current using a current being conducted by the transistor. (Block 1936). In example operations, the level divider circuitry 1430, 1455 produce the signal voltage (VSIG(ID_MX)) based on the voltage (VCM(ID_MX)) from the common mode circuitry 1425, 1450, which represents the current flowing through the transistors 315, 320. For example, the transistor 1585 generates the signal voltage (VSIG(ID_M1)) responsive to the voltage (VCM(ID MI)) from the resistor 1550. Similarly, the transistor 1670 generates the signal voltage (VSIG(ID_M2)) responsive to the voltage (VCM(ID_M2)) from the resistors 1635. In such example operations, the signal voltage (VSIG(ID_MX)) represents the current flowing through one of the transistors 315, 320.

[0188] The comparator 1710 determines if the signal current is greater than the first COL current. (Block 1940). In example operations, the switch circuitry 1705 provides the first COL voltage (VLVLI(COL ID MX)) to the comparator 1710. The comparator 1710 compares the first COL voltage (VLVLI(COL ID MX)) to the signal voltage (VSIG(ID_MX)). For example,the first COL voltage (VLVLI(C0L_ID_M1)) represents the corresponding current of the COL curve 1840 for the drain-to-source voltage (VDS) of the transistor 315. Similarly, the first COL voltage (VLVLI(COL_ID_M2)) represents the corresponding current of the COL curve 1840 for the drain-to-source voltage (VDS) of the transistor 320. In such example operations, the comparator 1710 determines if the current through the transistors 315, 320 is greater than the current of the COL curve 1840. Such a current is referred to as the first COL current. If the comparator 1710 determines the signal current is not greater than the first COL current (e.g., Block 1940 returns a result of NO), the comparator 1710 resets all timers. (Block 1944). Control proceeds to return to Block 505.

[0189] If the comparator 1710 determines the signal current is greater than the first COL current (e.g.. Block 1940 returns a result of YES), the timer circuitry 1725 starts a first timer. (Block 1948). In example operations, if the switch circuitry 1705 is providing the first COL voltage (VLVLI(COL_ID_MX)) to the comparator 1710, the switch circuitry 1720 provides the output of the comparator 1710 to the timer circuitry 1725. In some examples, the deglitch circuitry 1715 filters relatively high-frequency changes in the output of the comparator 1710. In such example operations, the timer circuitry 1725 starts a first timer responsive to the comparator 1710 determining the current through one of the transistors 315, 320 is greater than the current represented by the first COL voltage (VLVLI(COL_ID_MX)). For example, the timer circuitry 1725 starts the first timer responsive to the current through the transistor 315 exceeding the corresponding cunent of the COL curve 1840. In such examples, the timer circuitry 1725 begins to track the duration of time that the current through the transistor 315 exceeds the COL curve 1840. Similarly, the timer circuitry 1725 starts the first timer responsive to the current through the transistor 320 exceeding the corresponding current of the COL curve 1840. In such examples, the timer circuitry 1725 begins to track the duration of time that the current through the transistor 320 exceeds the COL curve 1840.

[0190] The comparator 1710 determines if the signal current is greater than the second COL current. (Block 1952). In example operations, the switch circuitry 1705 provides the second COL voltage (VLVL2(COL_ID_MX)) to the comparator 1710. The comparator 1710 compares the second COL voltage (VLVL2(COL_ID_MX)) to the signal voltage (VSIG(ID MX)). For example, the second COL voltage (VLVL2(COL_ID_M1)) represents the corresponding current of the COL curve 1850 for the drain-to-source voltage (VDS) of the transistor 315. Similarly, the second COL voltage (VLVL2(COL_ID_M2)) represents the corresponding current of the COL curve 1850 for the drain-to-source voltage (VDS) of the transistor 320. In such example operations, the comparator 1710 determines if the current through the transistors 315, 320 isgreater than the current of the COL curve 1850. Such a current is referred to as the second COL current.

[0191] If the comparator 1710 determines the signal current is greater than the second COL current(e.g., Block 1952 returns a result ofYES), the timer circuitry 1730 starts a second timer. (Block 1956). In example operations, if the switch circuitry71705 is providing the second COL voltage (VLVL2(COL_ID_MX)) to the comparator 1710, the switch circuitry 1720 provides the output of the comparator 1710 to the timer circuitry 1730. In such example operations, the timer circuitry 1730 starts a second timer responsive to the comparator 1710 determining the current through one of the transistors 315, 320 is greater than the current represented by the second COL voltage (VLVL2(COL_ID_MX)). For example, the timer circuitry 1730 starts the second timer responsive to the current through the transistor 315 exceeding the corresponding current of the COL curve 1850. In such examples, the timer circuitry 1730 begins to track the duration of time that the current through the transistor 315 exceeds the COL curve 1850. Similarly, the timer circuitry 1730 starts the second timer responsive to the current through the transistor 320 exceeding the corresponding current of the COL curve 1850. In such examples, the timer circuitry 1730 begins to track the duration of time that the current through the transistor 320 exceeds the COL curve 1850.

[0192] The comparator 1710 determines if the signal current is greater than the third COL current. (Block 1960). In example operations, the switch circuitry 1705 provides the third COL voltage (VLVL3(COL ID MX)) to the comparator 1710. The comparator 1710 compares the third COL voltage (VLVL3(COL_ID_MX)) to the signal voltage (VSIG(ID_MX)). For example, the third COL voltage (VLVL3(COL_ID_M1)) represents the corresponding current of the COL curve 1860 for the drain-to-source voltage (YDS) of the transistor 315. Similarly, the third COL voltage (VLVL3(COL_ID_M2)) represents the corresponding current of the COL curve 1860 for the drain-to-source voltage (VDS) of the transistor 320. In such example operations, the comparator 1710 determines if the current through the transistors 315, 320 is greater than the current of the COL curve 1860. Such a current is referred to as the third COL current.

[0193] If the comparator 1710 determines the signal current is not greater than the second COL current (e.g., Block 1952 returns a result of NO) or the comparator 1710 determines the signal current is not greater than the third COL current (e.g.. Block 1960 returns a result of NO), the timer circuitry 1725, 1730 determines if any timers are greater than a corresponding threshold. (Block 1964). In example operations, the timer circuitry 1725, 1730 have threshold times that represent an acceptable amount of time the transistors 315. 320 can operate beyond the corresponding one of the COL curves 1840, 1850, 1860. For example, the timer circuitry1725 has a first threshold time, the timer circuitry 1730 has a second threshold time, and the timer circuitry 1735 has a third threshold time. Such threshold times are further illustrated and described in connection with FIG. 20. If the OT threshold circuitry 1740 determines that none of the timers are greater than a corresponding threshold (e.g., Block 1964 returns a result of NO), control proceeds to return to Block 505.

[0194] If the OT threshold circuitry 1740 determines that one of the timers is greater than the corresponding threshold (e.g., Block 1964 returns a result of YES), the OT threshold circuitry 1740 adjusts the over temperature threshold. (Block 1968). In example operations, the timer circuitry 1725, 1730, 1735 generate a level COL indication (COL_LVL1, COL_LVL2, COL_LVL3) responsive to the timer exceeding the respective threshold time. In such example operations, the OT threshold circuitry 1740 sets the dynamic overtemperature threshold (DYN THRESH) based on the level corresponding to the level COL indication. For example, the OT threshold circuitry 1740 sets the dynamic overtemperature threshold (DYN_THRESH) to a first overtemperature threshold responsive to receiving the level one COL indication (COL LVLl). In such examples, the OT threshold circuitry 1740 sets the dynamic overtemperature threshold (DYN THRESH) to a second overtemperature threshold responsive to receiving the level two COL indication (COL LVL2). In both examples, the OT threshold circuitry 1740 reduces the dynamic overtemperature threshold (DYN THRESH) of the temperature monitor circuitry 420. Advantageously, as the dynamic overtemperature threshold (DYN THRESH) decreases, the response time of the temperature monitor circuitry 420 decreases.

[0195] If the comparator 1710 determines the signal current is greater than the third COL current (e.g., Block 1960 returns a result of YES), the timer circuitry 1735 starts a third timer. (Block 1972). In example operations, if the switch circuitry 1705 is providing the third COL voltage (VLVL3(COL_ID_MX)) to the comparator 1710, the switch circuitry 1720 provides the output of the comparator 1710 to the timer circuitry 1735. In such example operations, the timer circuitry 1735 starts a third timer responsive to the comparator 1710 determining the current through one of the transistors 315, 320 is greater than the current represented by the third COL voltage (VLVL3(COL_ID_MX)). For example, the timer circuitry 1735 starts the third timer responsive to the current through the transistor 315 exceeding the corresponding current of the COL curve 1860. In such examples, the timer circuitry 1735 begins to track the duration of time that the current through the transistor 315 exceeds the COL curve 1860. Similarly, the timer circuitry 1735 starts the third timer responsive to the current through the transistor 320 exceeding the corresponding current of the COL curve 1860. In such examples,the timer circuitry 1735 begins to track the duration of time that the current through the transistor 320 exceeds the COL curve 1860.

[0196] The timer circuitry 1735 determines if the third timer is greater than a third threshold. (Block 1976). In example operations, the timer circuitry 1735 has a third threshold time that represents an acceptable amount of time the transistors 315, 320 can operate beyond the COL curve 1860. The third threshold time is further illustrated and described in connection with FIG. 20. If the timer circuitry 1735 determines that the third timer is not greater than the third threshold (e.g., Block 1976 returns a result of NO), control proceeds to return to Block 505.

[0197] If the temperature monitor circuitry 420 determines the temperature of the transistor is greater than the overtemperature threshold (e.g., Block 510 returns a result of YES) or the timer circuitry 1735 determines that the third timer is greater than the third threshold (e.g., Block 1976 returns a result of YES), the shutdown circuitry 430 shuts down the transistor. (Block 550). In example operations, the temperature monitor circuitry 420 produces the temperature shutdown indication (TEMP_SHUTDOWN) responsive to the determination that the temperature of the transistors 315, 320 exceed the overtemperature threshold. In some examples, such as in FIG. 21, the timer circuitry 1735 or more generally the level monitor circuitry 1435, 1460 produce the direct shutdown indication (DIRECT SHUTDOWN) responsive to the third timer exceeding the third threshold time. In such examples, the severity of the level three COL curve (e.g., the COL curve 1860) is high enough to where operation beyond the third threshold time is likely to result in damage to the transistors 315. 320. In such example operations, the shutdown circuitry 430 disables the transistors 315, 320 or more generally the amplifier circuitry 140 responsive to receiving the temperature shutdown indication (TEMP SHUTDOWN) or the direct shutdown indication (DIRECT SHUTDOWN).

[0198] Control proceeds to End. Example methods are described with reference to the flowchart illustrated in FIGs. 19A and 19B. However, many other methods of implementing the load diagnostic circuitry 1300 of FIG. 13 may also be used in this description. For example, the order of execution of the blocks may be changed, or some of the blocks described may be changed, eliminated, or combined. Similarly, additional operations may be included in the manufacturing process before, in between, or after the blocks shown in the illustrated examples.

[0199] FIG. 20 is a timing diagram 2000 of example operations of the amplifier circuitry' 140 of FIGs. 1, 2, and 3 and the load diagnostic circuitry 1300 of FIG. 13, according to an embodiment of the present description. In the example of FIG. 20, the timing diagram 2000illustrates an amplifier output voltage 2010, an amplifier output current 2020, a first comparator output 2030, a second comparator output 2040. and a third comparator output 2050.

[0200] The amplifier output voltage 2010 represents the voltage at the output signal (OUTM) of the amplifier circuitry 140. In some examples, the amplifier output voltage 2010 represents the source voltage (Vs) of the transistor 315 and the drain voltage (VD) of the transistor 320. The amplifier output voltage 2010 is another example of the amplifier output 910.

[0201] The amplifier output current 2020 represents the current at the output signal (OUTM) of the amplifier circuitry' 140. In some examples, the amplifier output current 2020 represents the current (ID) through the transistors 315, 320.

[0202] The comparator output 2030 represents the output of the comparator 1710 for a comparison of the first COL voltage (Vi,vi.i(COL_ID_MX)) to the signal voltage (VSIG(ID_MX)). In the example of FIG. 20, the signal voltage (VSIG(ID_MX)) represents the current through the transistors 315, 320, which is illustrated as the amplifier output current 2020. The comparator output 2040 represents the output of the comparator 1710 for a comparison of the second COL voltage (VLVL2(COL_ID_MX)) to the signal voltage (VSIG(ID_MX)). The comparator output 2050 represents the output of the comparator 1710 for a comparison of the third COL voltage (VLVL3(COL_ID_MX)) to the signal voltage (VSIG(ID MX)).

[0203] In the example of FIG. 20. at the time 2060. the output signal (OUTM) of the amplifier circuitry 140 is shorted to the output signal (OUTP) of the amplifier circuitry 130. During the next transition between saturated states of the amplifier output voltage 2010, the short of at the output of the amplifier circuitry 130 begins to produce excess currents through the transistors 315, 320. For example, at the time 2070, the amplifier output current 2020 exceeds one amp. In some examples, if the first COL voltage (VLVLI(COL_ID_MX)) represents one amp, the output of the comparator output 2030 starts the timer circuitry 1725.

[0204] In another example, at the time 2080, the amplifier output current 2020 exceeds two and seven tenths’ amps. In such examples, if the second COL voltage (VLVL2(COL_ID_MX)) represents two and seven tenths’ amps, the output of the comparator output 2040 starts the timer circuitry 1730.

[0205] In yet another example, at the time 2090, the amplifier output current 2020 exceeds seven amps. In such examples, if the third COL voltage (VLVL3(COL_ID_MX)) represents seven amps, the output of the comparator output 2050 starts the timer circuitry 1735.

[0206] In the described examples, the timer circuitry' 1725, 1730, 1735 continue to track the time the amplifier output current 2020 exceeds the COL currents corresponding to the COL voltages (VLVLI(COL ID MX), VLVL2(COL_ID_MX), VLVL3(COLJD_MX)). However, at the time 2095, the amplifier output voltage 2010 is saturated. During such time, the transistors 315, 320 operate in the clamp region 1870. Upon entering the clamp region 1870, the COL monitor circuitry’ 1310 waits for the next transition. Advantageously, the COL monitor circuitry 1310 allows the transistors 315, 320 to continue to operate beyond the COL curves 1840, 1850, 1860.

[0207] FIG. 21 is a block diagram of load diagnostic circuitry 2100, yvhich is another example implementation of the load diagnostic circuitry' 175 of FIG. 3, e.g., to safely operate the transistor 315, 320 of FIG. 3, according to an embodiment of the present description.

[0208] In some embodiments, load diagnostic circuitry 2100 may be implemented using a processor or controller coupled to a memory and configured to execute instructions from such memory. Some embodiments may be implemented or include a central processor unit (CPU), a field programmable gate array (FPGA). a hardyvare accelerator, and / or a state machine. In some embodiments, load diagnostic circuitry 2100 is implemented with synthesized logic. In some embodiments, load diagnostic circuitry 2100 is implemented in hardware only. In some embodiments, load diagnostic circuitry’ 2100 is configurable via registers. Other implementations may also be possible.

[0209] In the example of FIG. 21 , the load diagnostic circuitry 2100 includes the temperature monitor circuitry 420 of FIGs. 4 and 13, the shutdoyvn circuitry 430 of FIGs. 4 and 13, and the COL monitor circuitry' 1310 of FIG. 13.

[0210] In the example of FIG. 21, the load diagnostic circuitry' 2100 includes the COL monitor circuitry 1310 for both direct shutdown and dynamically changing the overtemperature threshold. In some examples, such as FIG. 4, the COL monitor circuitry 1310 may be structured to produce only the direct shutdoyvn indication (DIRECT SHUTDOWN). In other examples, such as in FIG. 13, the COL monitor circuitry’ 1310 may be structured to dynamically adjust the overtemperature threshold of the temperature monitor circuitry 420. In yet another example, as illustrated in FIG. 21, the COL monitor circuitry 1310 may produce both the direct shutdown indication (DIRECT SHUTDOWN) and the dynamic overtemperature threshold (DYN TRESHOLD). Advantageously, the COL monitor circuitry 1310 reduces the likelihood of adverse current conditions from damaging the transistors 315, 320. For example, the COL monitor circuitry 1310 detects a weak short across one of the transistors 315, 320 responsive to a drain current exceeding the COL curve 610.

[0211] Examples of the present description are summarized here. Other embodiments are described in the specification.

[0212] Example 1. A device including: a transistor having a first terminal and a control terminal; continuous operating loss (COL) fit circuitry having an input and an output; current sense circuitry having a first input, a second input, and an output, the first input of the current sense circuitry coupled to the first terminal of the transistor and the input of the COL fit circuitry, the second input of the current sense circuitry coupled to the control terminal of the transistor; and comparator circuitry having a first input and a second input, the first input of the comparator circuitry coupled to the output of the COL fit circuitry', the second input of the comparator circuitry coupled of the output of the current sense circuitry.

[0213] Example 2. The device of example 1. further including voltage-to-current (V-I) circuitry having an input and an output, the input of the V-I circuitry coupled to the first terminal of the transistor, the output of the V-I circuitry coupled to the input of the COL fit circuitry7.

[0214] Example 3. The device of one of examples 1 or 2, where the comparator circuitry further has an output, and the device is further including: gate-to-source voltage (VGS) detect circuitry having an input and an output, the input of the VGS detect circuitry coupled to the control terminal of the transistor; and logic circuitry' having a first input and a second input, the first input of the logic circuitry coupled to the output of the comparator circuitry, the second input of the logic circuitry coupled to the output of the VGS detect circuitry.

[0215] Example 4. The device of one of examples 1 to 3, where the comparator circuitry further has an output, and the device further includes timer circuitry' having an input coupled to the output of the comparator circuitry.

[0216] Example 5. The device of one of examples 1 to 4. where the COL fit circuitry includes: voltage-to-current (V-I) circuitry having an input and an output, the input of the V-I circuitry coupled to the first terminal of the transistor; current mirror circuitry' having an input and an output, the input of the current mirror circuitry' coupled to the output of the V-I circuitry'; and level divider circuitry having an input and an output, the input of the level divider circuitry coupled to the output of the current mirror circuitry, the output of the level divider circuitry coupled to the first input of the comparator circuitry.

[0217] Example 6. The device of one of examples 1 to 5, where the comparator circuitry' further has an output, the output of the level divider circuitry is a first output, the level divider circuitry further having a second output, and the device further including: first switch circuitry having a first input, a second input, and an output, the first input of the first switch circuitrycoupled to the first output of the level divider circuitry, the second input of the first switch circuitry coupled to the second output of the level divider circuitry, the output of the first switch circuitry coupled to the first input of the comparator circuitry; second switch circuitry having an input, a first output, and a second output, the input of the second switch circuitry coupled to the output of the comparator circuitry'; first timer circuitry having an input coupled to the first output of the second switch circuitry; and second timer circuitry having an input coupled to the second output of the second switch circuitry’.

[0218] Example 7. The device of one of examples 1 to 6, where the first timer circuitry further has an output, the second timer circuitry further has an output, and the device further including: over temperature (OT) threshold circuitry' having a first input, a second input, and an output, the first input of the OT threshold circuitry’ coupled to the output of the first timer circuitry, the second input of the OT threshold circuitry coupled to the output of the second timer circuitry; temperature monitor circuitry having a first input and a second input, the first input of the temperature monitor circuitry coupled to the output of the OT threshold circuitry'; and a temperature sensor having an output coupled to the second input of the temperature monitor circuitry, the temperature sensor mechanically coupled to the transistor.

[0219] Example 8. The device of one of examples 1 to 7, where the first timer circuitry further has an output, and the device further including shutdow n circuitry' having an input and an output, the input of the shutdow n circuitry coupled to the output of the first timer circuitry, the output of the shutdown circuitry coupled to the control terminal of the transistor.

[0220] Example 9. The device of one of examples 1 to 8, where the transistor is a first transistor, the device is further including: a second transistor having a terminal; amplifier circuitry having an output; and filter circuitry having a first input and a second input, the first input of the filter circuitry coupled to the first terminal of the first transistor and the terminal of the second transistor, the second input of the filter circuitry coupled to the output of the amplifier circuitry.

[0221] Example 10. A device including: a transistor; and load diagnostic circuitry coupled to the transistor, the load diagnostic circuitry configured to: determine a drain-to-source voltage of the transistor; determine a drain current of the transistor; determine a continuous operating loss (COL) current of the transistor using the drain-to-source voltage; compare the drain current to the COL current; and determine an operating condition of the transistor responsive to the comparison.

[0222] Example 11. The device of example 10. where the transistor is a first transistor, the drain-to-source voltage is a first drain-to-source voltage, the device further including a secondtransistor, and the load diagnostic circuitry is further configured to determine a second drain-to-source voltage of the second transistor using the first drain-to-source voltage of the first transistor.

[0223] Example 12. The device of one of examples 10 or 11, where the load diagnostic circuitry7is further configured to: start a timer responsive to the drain current being greater than the COL current; and shutdow n the transistor responsive to a determination that the timer is greater than a threshold time.

[0224] Example 13. The device of one of examples 10 to 12, where the load diagnostic circuitry is further configured to: start a timer responsive to the drain current being greater than the COL current; and adjust an overtemperature threshold responsive to a determination that the timer is greater than a threshold time.

[0225] Example 14. The device of one of examples 10 to 13, where the COL current is a first COL current, the load diagnostic circuitry further configured to: determine a second COL current using the drain-to-source voltage, the second COL current greater than the first COL current; and compare the drain current to the first COL current and the second COL current.

[0226] Example 15. The device of one of examples 10 to 14, where the load diagnostic circuitry is further configured to: start a first timer responsive to the drain current being greater than the first COL current; start a second timer responsive to the drain current being greater than the second COL current; adjust an overtemperature threshold responsive to a determination that the first timer is greater than a threshold time; and shutdown the transistor responsive to a determination that the second timer is greater than a second threshold time.

[0227] Example 16. The device of one of examples 10 to 15, further including a temperature sensor coupled to the load diagnostic circuitry', where the load diagnostic circuitry' is further configured to: determine a temperature of the transistor using the temperature sensor; compare the temperature to an overtemperature threshold; and detect thermal runaway of the transistor using the comparison.

[0228] Example 17. A device including: filter circuitry ; first amplifier circuitry coupled to the filter circuitry; second amplifier circuitry coupled to the filter circuitry’ and the first amplifier circuitry; and load diagnostic circuitry coupled to the second amplifier circuitry, the load diagnostic circuitry configured to determine a continuous operating loss (COL) current using voltages of the second amplifier circuitry’.

[0229] Example 18. The device of example 17, where the second amplifier circuitry includes a transistor, and where the load diagnostic circuitry is further configured to: determine a drain-to-source voltage of the transistor; determine a drain current of the transistor; and determine the COL cunent of the transistor using the drain-to-source voltage.

[0230] Example 19. The device of one of examples 17 or 18, where the load diagnostic circuitry is further configured to: compare the COL current to a current of the second amplifier circuitry; start a timer based on the comparison; and shutdown the second amplifier circuitry responsive to a determination that the timer is greater than a threshold time.

[0231] Example 20. The device of one of examples 17 to 19, where the load diagnostic circuitry is further configured to: compare the COL current to a current of the second amplifier circuitry; start a timer based on the comparison; and adjust an overtemperature threshold responsive to a determination that the timer is greater than a threshold time.

[0232] Example 21. The device of one of examples 17 to 20, where the COL current is a first COL current, the load diagnostic circuitry further configured to: determine a second COL current using voltages of the second amplifier circuitry, the second COL current greater than the first COL current; and compare a current of the second amplifier circuitry to the first COL current and the second COL current.

[0233] Example 22. The device of one of examples 17 to 21, where the load diagnostic circuitry is further configured to: start a first timer responsive to the current of the second amplifier circuitry being greater than the first COL current; start a second timer responsive to the current of the second amplifier circuitry being greater than the second COL current; adjust an overtemperature threshold responsive to a determination that the first timer is greater than a threshold time; and shutdown the second amplifier circuitry responsive to a determination that the second timer is greater than a second threshold time.

[0234] Example 23. The device of one of examples 17 to 22, further including a temperature sensor coupled to the load diagnostic circuitry, where the load diagnostic circuitry is further configured to: determine a temperature of the second amplifier circuitry using the temperature sensor; compare the temperature to an overtemperature threshold; and detect thermal runaway of the second amplifier circuitry using the comparison.

[0235] Example 24. The device of one of examples 17 to 23, where the second amplifier circuitry includes a transistor, and the voltages of the second amplifier circuitry includes a drain-to-source voltage of the transistor.

[0236] Example 25. The device of one of examples 17 to 24, further including a speaker coupled to the filter circuitry.

[0237] Example 26. The device of one of examples 17 to 25. where the first amplifier circuitry includes a Class-D amplifier having an output configured to be coupled to a speaker,and where the second amplifier circuitry is configured to be coupled to the speaker without an intervening inductor.

[0238] As used herein, ‘'approximately” and ‘'about” modify their subjects / values to recognize the potential presence of variations that occur in real world applications. For example, “approximately” and “about” may modify dimensions that may not be exact due to at least one of manufacturing tolerances or other real-world imperfections. For example, “approximately” and “about” may indicate such dimensions may be within a tolerance range of + / - 10% unless otherwise specified herein.

[0239] Circuits described herein may be reconfigurable to include the replaced components to provide functionality at least partially similar to functionality available prior to the component replacement. Components shown as resistors, unless otherwise stated, are generally representative of any one or more elements coupled in at least one of series or parallel to provide an amount of impedance represented by the shown resistor. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in series between the same two nodes as the single resistor or capacitor. While certain elements of the described examples are included in an integrated circuit and other elements are external to the integrated circuit, in other examples, additional or fewer features may be incorporated into the integrated circuit. In addition, some or all of the features illustrated as being external to the integrated circuit may be included in the integrated circuit and some features illustrated as being internal to the integrated circuit may be incorporated outside of the integrated. As used herein, the term “integrated circuit” means one or more circuits that are at least one of (i) incorporated in / over a semiconductor substrate; (ii) incorporated in a single semiconductor package; (iii) incorporated into the same module; or (iv) incorporated in / on the same printed circuit board.

[0240] Modifications are possible in the described embodiments, and other embodiments are possible, within the scope of the claims.

Claims

CLAIMSWhat is claimed is:

1. A device comprising:a transistor having a first terminal and a control terminal;continuous operating loss (COL) fit circuitry having an input and an output; current sense circuitry having a first input, a second input, and an output, the first input of the current sense circuitry coupled to the first terminal of the transistor and the input of the COL fit circuitry, the second input of the current sense circuitry coupled to the control terminal of the transistor; andcomparator circuitry having a first input and a second input, the first input of the comparator circuitry coupled to the output of the COL fit circuitry, the second input of the comparator circuitry coupled of the output of the current sense circuitry.

2. The device of claim 1, further comprising voltage-to-current (V-I) circuitry having an input and an output, the input of the V-I circuitry coupled to the first terminal of the transistor, the output of the V-I circuitry coupled to the input of the COL fit circuitry.

3. The device of claim 1, in which the comparator circuitry further has an output, and the device is further comprising:gate-to-source voltage (VGS) detect circuitry having an input and an output, the input of the VGS detect circuitry coupled to the control terminal of the transistor; and logic circuitry having a first input and a second input, the first input of the logic circuitry coupled to the output of the comparator circuitry, the second input of the logic circuitry coupled to the output of the VGS detect circuitry.

4. The device of claim 1, in which the comparator circuitry further has an output, and the device further comprises timer circuitry having an input coupled to the output of the comparator circuitry.

5. The device of claim 1, in which the COL fit circuitry includes:voltage-to-current (V-I) circuitry having an input and an output, the input of the V-I circuitry coupled to the first terminal of the transistor;cunent mirror circuitry having an input and an output, the input of the current mirror circuitry coupled to the output of the V-I circuitry; andlevel divider circuitry having an input and an output, the input of the level divider circuitry coupled to the output of the current mirror circuitry, the output of the level divider circuitry coupled to the first input of the comparator circuitry.

6. The device of claim 5, in which the comparator circuitry further has an output, theoutput of the level divider circuitry is a first output, the level divider circuitry further having a second output, and the device further comprising:first switch circuitry having a first input, a second input, and an output, the first input of the first switch circuitry coupled to the first output of the level divider circuitry, the second input of the first switch circuitry coupled to the second output of the level divider circuitry7, the output of the first switch circuitry coupled to the first input of the comparator circuitry;second switch circuitry having an input, a first output, and a second output, the input of the second switch circuitry coupled to the output of the comparator circuitry;first timer circuitry having an input coupled to the first output of the second switch circuitry; andsecond timer circuitry7having an input coupled to the second output of the second switch circuitry.

7. The device of claim 6, in which the first timer circuitry7further has an output, the second timer circuitry7further has an output, and the device further comprising:over temperature (OT) threshold circuitry having a first input, a second input, and an output, the first input of the OT threshold circuitry coupled to the output of the first timer circuitry, the second input of the OT threshold circuitry coupled to the output of the second timer circuitry7;temperature monitor circuitry having a first input and a second input, the first input of the temperature monitor circuitry coupled to the output of the OT threshold circuitry; and a temperature sensor having an output coupled to the second input of the temperature monitor circuitry7, the temperature sensor mechanically coupled to the transistor.

8. The device of claim 6, in which the first timer circuitry further has an output, and the device further comprising shutdown circuitry having an input and an output, the input of the shutdown circuitry coupled to the output of the first timer circuitry, the output of the shutdown circuitry coupled to the control terminal of the transistor.

9. The device of claim 1, in which the transistor is a first transistor, the device is further comprising:a second transistor having a terminal;amplifier circuitry having an output; andfilter circuitry7having a first input and a second input, the first input of the filter circuitry coupled to the first terminal of the first transistor and the terminal of the second transistor, the second input of the filter circuitry coupled to the output of the amplifier circuitry.

10. A device comprising:a transistor; andload diagnostic circuitry coupled to the transistor, the load diagnostic circuitry configured to:determine a drain-to-source voltage of the transistor;determine a drain current of the transistor;determine a continuous operating loss (COL) current of the transistor using the drain-to-source voltage;compare the drain current to the COL current; anddetermine an operating condition of the transistor responsive to the comparison.

11. The device of claim 10, in which the transistor is a first transistor, the drain-to-source voltage is a first drain-to-source voltage, the device further comprising a second transistor, and the load diagnostic circuitry is further configured to determine a second drain-to-source voltage of the second transistor using the first drain-to-source voltage of the first transistor.

12. The device of claim 10, in which the load diagnostic circuitry is further configured to:start a timer responsive to the drain current being greater than the COL current; and shutdown the transistor responsive to a determination that the timer is greater than a threshold time.

13. The device of claim 10, in which the load diagnostic circuitry' is further configured to:start a timer responsive to the drain current being greater than the COL current; and adjust an overtemperature threshold responsive to a determination that the timer is greater than a threshold time.

14. The device of claim 10, in which the COL current is a first COL current, the load diagnostic circuitry further configured to:determine a second COL current using the drain-to-source voltage, the second COL current greater than the first COL current; andcompare the drain current to the first COL current and the second COL current.

15. The device of claim 14, in which the load diagnostic circuitry is further configured to:start a first timer responsive to the drain current being greater than the first COL current; start a second timer responsive to the drain current being greater than the second COL current;adjust an overtemperature threshold responsive to a determination that the first timer is greater than a threshold time; andshutdown the transistor responsive to a determination that the second timer is greater than a second threshold time.

16. The device of claim 10, further comprising a temperature sensor coupled to the load diagnostic circuitry, in which the load diagnostic circuitry is further configured to:determine a temperature of the transistor using the temperature sensor;compare the temperature to an overtemperature threshold; anddetect thermal runaway of the transistor using the comparison.

17. A device comprising:filter circuitry;first amplifier circuitry coupled to the filter circuitry;second amplifier circuitry coupled to the filter circuitry' and the first amplifier circuitry'; andload diagnostic circuitry coupled to the second amplifier circuitry’, the load diagnostic circuitry configured to determine a continuous operating loss (COL) current using voltages of the second amplifier circuitry.

18. The device of claim 17, in which the second amplifier circuitry’ includes a transistor, and in which the load diagnostic circuitry is further configured to:determine a drain-to-source voltage of the transistor;determine a drain current of the transistor; anddetermine the COL current of the transistor using the drain-to-source voltage.

19. The device of claim 17, in which the load diagnostic circuitry is further configured to:compare the COL current to a current of the second amplifier circuitry;start a timer based on the comparison; andshutdown the second amplifier circuitry' responsive to a determination that the timer is greater than a threshold time.

20. The device of claim 17, in which the load diagnostic circuitry is further configured to:compare the COL current to a current of the second amplifier circuitry;start a timer based on the comparison; andadjust an overtemperature threshold responsive to a determination that the timer is greater than a threshold time.

21. The device of claim 17, in which the COL current is a first COL current, the load diagnostic circuitry further configured to:determine a second COL current using voltages of the second amplifier circuitry', the second COL current greater than the first COL current; andcompare a cunent of the second amplifier circuitry’ to the first COL current and the second COL current.

22. The device of claim 21, in which the load diagnostic circuitry is further configured to: start a first timer responsive to the current of the second amplifier circuitry being greater than the first COL cunent;start a second timer responsive to the current of the second amplifier circuitry being greater than the second COL current;adjust an overtemperature threshold responsive to a determination that the first timer is greater than a threshold time; andshutdown the second amplifier circuitry responsive to a determination that the second timer is greater than a second threshold time.

23. The device of claim 17, further comprising a temperature sensor coupled to the load diagnostic circuitry, in which the load diagnostic circuitry is further configured to:determine a temperature of the second amplifier circuitry using the temperature sensor; compare the temperature to an overtemperature threshold; anddetect thermal runaway of the second amplifier circuitry using the comparison.

24. The device of claim 17, in which the second amplifier circuitry includes a transistor, and the voltages of the second amplifier circuitry includes a drain-to-source voltage of the transistor.

25. The device of claim 17, further comprising a speaker coupled to the filter circuitry.

26. The device of claim 17, in which the first amplifier circuitry comprises a Class-D amplifier having an output configured to be coupled to a speaker, and in which the second amplifier circuitry is configured to be coupled to the speaker without an intervening inductor.

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