Intelligent electronic switch

Abstract

Embodiments of the present disclosure generally relate to intelligent electronic switches. An integrated circuit is described herein. According to one embodiment, the circuit includes a transistor coupled between a power pin and an output pin; a current output circuit configured to provide a diagnostic current at the current output pin; and a current sensing circuit coupled to the transistor and configured to generate a first current sensing signal indicating a load current through the transistor and a second current sensing signal indicating the load current. The current output circuit is configured to select one of the following as the diagnostic current based on a control signal: the first current sensing signal and the second current sensing signal.

Description

Technical Field

[0001] The present disclosure relates to the field of intelligent semiconductor switches. Background Art

[0002] Almost every electrical device (e.g., in a car, in a house, in the electrical subsystems of a large installation) includes one or more fuses to provide overcurrent protection. A standard fuse includes a wire that provides a low-ohmic current path as long as the current through the fuse is below the nominal current. However, when the current through the fuse exceeds the nominal current for a certain period of time, the wire is designed to heat up and melt or vaporize, so once triggered, the fuse must be replaced with a new one.

[0003] Fuses are increasingly being replaced by circuit breakers. A circuit breaker is an automatically operated electrical switch designed to protect a circuit from damage caused by overcurrent, overload or short circuit. A circuit breaker may include an electromechanical relay that triggers the relay to disconnect the protected circuit from the power supply when an overcurrent (i.e., a current exceeding the nominal current) is detected. In many applications (e.g., in an onboard power supply of a car), a circuit breaker may be implemented using an electronic switch (e.g., MOS transistor, IGBT, etc.) to disconnect the protected circuit from the power supply in the event of an overcurrent. Such an electronic circuit breaker may also be referred to as an electronic fuse (e-fuse or smart fuse). In addition to being used as a circuit breaker, an electronic fuse may also be used to periodically turn on and off a load. Typically, a so-called driver circuit or a simple driver (a gate driver in the case of a MOS transistor) is used to control the switching state (on / off) of an electronic switch such as a MOS transistor.

[0004] However, at least in some electronic circuit breakers (electronic fuses or e-fuses), the fault tolerance and functional safety of common driver circuits may be less than perfect, which may be problematic in automotive applications that must comply with standards on functional safety (e.g., ISO26262). In fact, e-fuses need to be more than just traditional fuses with electronic switches. Reliable implementation of e-fuses entails various challenges. Summary of the invention

[0005] An integrated circuit is described herein. According to one embodiment, the circuit includes a transistor coupled between a power pin and an output pin; a current output circuit configured to provide a diagnostic current at the current output pin; and a current sensing circuit coupled to the transistor and configured to generate a first current sensing signal indicating a load current through the transistor and a second current sensing signal indicating the load current. The current output circuit is configured to select one of the following as the diagnostic current based on a control signal: the first current sensing signal and the second current sensing signal.

[0006] Further, according to one embodiment, a method is described, the method comprising: establishing a load current path between a power supply pin and an output pin by activating a transistor; generating a first current sensing signal indicating a load current through the transistor and a second current sensing signal indicating the load current; and selecting one of the following items: the first current sensing signal and the second current sensing signal according to a control signal. The selected signal is provided as a diagnostic current at a current output pin. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention may be better understood with reference to the following drawings and description. The components in the drawings are not necessarily drawn to scale; instead, emphasis is placed on illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals indicate corresponding parts. In the drawings,

[0008] Figure 1 An example of an electronic fuse circuit including an electronic switch and a control circuit configured to drive the electronic switch and an exemplary application of the electronic fuse circuit are schematically shown.

[0009] Figure 2 Shown in more detail Figure 1 An example of a control circuit.

[0010] Figure 3 Shown for Figure 2 An example of a control circuit logic circuit.

[0011] Figure 4 Shows the description Figure 2 A timing diagram of the control circuit functionality is shown.

[0012] Figure 5 A is shown as 0.35mm 2 Plot of a family of characteristic curves (time versus current) for a cable and different maximum cable temperatures.

[0013] Figure 5 B is a graph showing a family of characteristic curves (time versus current) for a maximum cable temperature of 25 Kelvin above ambient temperature and for different cable cross sections.

[0014] Figure 6 Shown for Figure 2 An example of an example monitoring circuit.

[0015] Figure 7 A first example of an e-fuse ("smart fuse") circuit is shown which allows selection of the conductor cross section and the maximum cable temperature.

[0016] Figure 8 Shown for Figure 2 Another example of a monitoring circuit of an embodiment of the present invention.

[0017] Fig. 9 Shows that it can be Figure 8 Another example of a current sensing circuit that is used in conjunction with a monitoring circuit and provides a redundant current sensing signal.

[0018] Fig.10 Shows Fig. 9 An exemplary modification / enhancement of a previous example.

[0019] Figures 11 to 13 shows a method that allows checking the consistency of redundant current sensing signals. Fig. 9 Various modifications / enhancements of previous examples.

[0020] Fig.14 An exemplary use of an e-fuse circuit and its externally connected circuitry is shown.

[0021] Fig.15 A timing diagram is shown for illustrating the output of different information at one pin of an integrated e-fuse circuit. DETAILED DESCRIPTION

[0022] In the following detailed description, reference is made to the accompanying drawings. The accompanying drawings form part of the specification and, for illustrative purposes, show examples of ways in which the invention can be used and implemented. It should be understood that the features of the various embodiments described herein may be combined with each other unless otherwise specifically noted.

[0023] Figure 1 An example of an electronic circuit that can be used as an electronic fuse is shown. Therefore, the electronic circuit is also referred to as an electronic fuse circuit F. According to this example, the electronic fuse circuit includes an electronic switch 2, which has a control node 21 and a load current path between a first load node 22 and a second load node 23. The electronic circuit also includes a control circuit 1, which is coupled to the control node 21 of the electronic switch 2 and is configured to drive the electronic switch 2. The electronic fuse circuit F having the electronic switch 2 and the control circuit 1 can be monolithically integrated in one semiconductor die (chip), or can be integrated in two semiconductor dies, which are arranged in an integrated circuit package. The electronic fuse circuit F is configured to drive a load Z (the wires connecting the load are connected in Figure 1 The load Z may be connected in series with the load current path of the electronic switch 2 (shown as a dotted line in FIG. 1 ). Therefore, the series circuit of the load current path of the electronic switch 2 and the load Z may be connected between power supply nodes, where a positive power supply potential and a negative power supply potential or a ground potential GND (zero volt) may be provided. In the following, the voltage between the two power supply nodes is referred to as the power supply voltage VB The control circuit 1 can be controlled, for example, by the microcontroller 8 according to the input signal S IN To switch on and off the load current i through the load Z L However, depending on the application, the input signal S IN It can be generated by any other circuit system instead of a microcontroller.

[0024] In an exemplary application, the electronic fuse circuit F can be used to drive a load Z in a car. In this case, the supply voltage V B The power source of the load is the car battery. In general, "to drive the load" may include: switching on or off the load current through the load by switching the electronic switch 2 on or off. The load may be any load used in a car. Examples of load Z include, among others, different types of lamps, different types of motors, relays, heating systems, etc. Figure 1 In the example shown, the electronic switch 2 and the load Z are connected in a high-side configuration. That is, the load Z is connected between the electronic switch 2 and the ground node GND. However, this is only an example. The electronic switch 2 and the load Z can also be connected in a low-side configuration or in any other configuration. For example, in a low-side configuration, the electronic switch is connected between the load Z and the ground node GND.

[0025] according to Figure 1 In an example, the load Z can be connected to the electronic switch 2 via a conductive wire (for example, which is included in a cable). Depending on the location of the electronic circuit and the corresponding load Z in the electrical installation of the car, the length of the wire may be quite long, several tens of centimeters or even longer (for example, up to 10m). Modern cars include a plurality of electrical loads, so that a plurality of wires are required to connect the various loads to their corresponding electronic switches. In order to save costs and resources, it may be desirable to determine the size of the various wires so that they withstand the nominal current of the connected loads for a long time. However, if the current rises above the rated current, the wire may be damaged or even destroyed due to overheating. According to an exemplary embodiment, the control circuit 1 may therefore have a current monitoring function in order to monitor the load current i through the electronic switch 2 (and the load Z). L The current monitoring allows the electronic switch 2 to be turned off when an overload scenario is detected, in order to protect the conductor (and the load Z). An “overload scenario” is when the electronic switch 2 is not turned off (within a certain time) to keep the conductor (and the load Z) from being connected to the supply voltage V B The disconnection of the power source (e.g., a car battery) may cause the wire or the load to be damaged or destroyed. The mechanism is further explained in detail below. Since the electronic fuse circuit F is configured to switch the load Z on and off and protect the wire, it is also referred to as a switch and protection circuit below.

[0026] exist Figure 1 In the example shown, the electronic switch 2 is schematically drawn as a circuit block including a switch. Hereinafter, the term "electronic switch" includes any type of electronic switch or electronic circuit system having a control node 21 and a load current path between a first load node 22 and a second load node 23, and is configured to be turned on and off according to a drive signal received at the control node 21, "turned on" means that the electronic switch 2 is operated in an on state, in which the electronic switch 2 can conduct current between the first load node 22 and the second load node 23. "Turn off" means that the electronic switch 2 is operated in an off state, in which the electronic switch 2 can prevent current from flowing between the first load node 22 and the second load node 23. According to an example, the electronic switch 2 includes at least one transistor. The at least one transistor can be, for example, a MOSFET (metal oxide semiconductor field effect transistor), an IGBT (insulated gate bipolar transistor), a JFET (junction field effect transistor), a BJT (bipolar junction transistor), or a HEMT (high electron mobility transistor).

[0027] In the following, examples of the control circuit 1 and its functions are described with reference to the accompanying drawings. In particular, the functions of the control circuit 1 are described with reference to the functional blocks depicted in the accompanying drawings. It should be noted that these functional blocks represent the functions of the control circuit 1, rather than their specific implementation. These functional blocks can be dedicated circuit blocks configured to perform the corresponding functions described below. However, the functions of the various functional blocks can also be performed by a programmable circuit (processor) configured to execute software / firmware stored in a memory.

[0028] Figure 2 FIG. 4 shows an exemplary implementation of the control circuit 1. In this example, the control circuit 1 includes a monitoring circuit 4, which is configured to monitor the load current i L The current-time characteristic of the load current i is used to generate the first protection signal OC. L The current time characteristic to generate the first protection signal OC" may include the monitoring circuit 4 processing the load current i L The monitoring circuit 4 evaluates the load current i L A certain period of time is required to generate the first protection signal OC. In order to evaluate the load current i L The monitoring circuit 4 receives the current sensing signal CS and generates the first protection signal OC based on the current sensing signal CS. The current sensing signal CS represents the load current i L , and according to one example, can be related to the load current i L Proportional. Figure 2In the example of FIG. 1 , the current sense signal CS is available at the sense output 24 of the electronic switch 2. In this case, it is configured to measure the load current i L And the current measurement circuit that provides the current sensing signal CS can be integrated in the electronic switch 2. However, this is only an example. It is also possible to use a current measurement circuit that is separate from the electronic switch 2. Various current sensing circuits (e.g., shunt resistors, sense-FET circuits, etc.) are known, so they are not described in detail herein. Figure 8 A specific example of a current sensing circuit is included in FIG. 1 and is discussed further below.

[0029] Figure 2 The control circuit 1 shown is configured to be based on the protection signal OC and the first input node (eg, input pin) P of the electronic fuse circuit F. IN The input signal S received at IN To drive the electronic switch 2. The protection signal OC and the input signal S IN is supplied to the logic circuit 3, which generates a signal based on the protection signal OC and the input signal S IN To generate the driving signal S ON . Drive signal S ON is directly or indirectly (eg, via the driver circuit 5) supplied to the control node 21 of the electronic switch 2 so as to switch the electronic switch 2 on or off. According to one example, the drive signal S ON The driver circuit 5 (or simply referred to as the driver) is configured to drive the electronic switch 2 based on the drive signal S ON The corresponding signal level is used to drive the electronic switch 2. The electronic switch 2 includes, for example, a transistor, such as a MOSFET (e.g. Figure 2 MOSFET is a voltage-controlled semiconductor device that is turned on or off according to a driving voltage applied between a gate node and a source node. In this example, the driver 5 is configured to be based on a driving signal S ON To generate the driving voltage (gate voltage V G ) to turn on or off the MOSFET according to the drive signal. When a MOSFET is used, the driver 5 is also called a gate driver.

[0030] Figure 3 The circuit of FIG. 1 shows an exemplary implementation of (a portion of) the logic circuit 3. In this example, the logic circuit 3 includes an inverter 33, an SR latch 31 (flip-flop), and an AND gate 32. The first input of the AND gate 32 is configured to receive an input signal S IN, and the reset input R of the SR latch 31 is configured to receive the inverted input signal provided by the inverter 33. The set input S of the SR latch 31 is configured to receive the first protection signal OC. The inverted output Q' of the SR latch 31 is connected to the second input of the AND gate 32. The drive signal S ON is provided at the output of AND gate 32 .

[0031] Figure 4 The timing diagram also shows the function of the logic circuit 3. The input signal S IN The initial low level of causes the reset of the SR latch 31, which produces a high level at the inverting output Q' of the SR latch 31. Thus, both inputs of the AND gate 32 "see" a high level, so the output of the AND gate 32 provides a high level drive signal S ON When the input signal S IN When it becomes low (it indicates that the electronic switch 2 is turned off, see Figure 4 , time t1 and t2), the AND gate 32 "sees" a low level at its first input, so the output of the AND gate 32 provides a low level drive signal S ON In other words, assuming that the SR latch 31 is in its reset state, the input signal S is fed through the logic circuit 3 IN (ie, the driving signal S ON Equal to the input signal S IN Once the SR latch 31 is set by the first protection signal OC becoming a high level, the inverting output Q' of the SR latch 31 is set to a low level (see Figure 4 , time t3). Thus, AND gate 32 sees a low level at its second input, and thus drives signal S ON is set to a low level. In other words, the input signal S IN is blanked by AND gate 32. The drive signal S ON Remains at a low level until the input signal S IN is set to a low level (which indicates the turning off of the electronic switch 2 and the resetting of the SR latch 31, see Figure 4 , time t4), and is set to a high level again (which indicates that the electronic switch 2 is turned on, see Figure 4 , time t5). Again, this can be achieved in various ways Figure 3 Functions of exemplary implementations.

[0032] As mentioned above, the wires connecting the load Z and the electronic fuse circuit F may be expected to withstand the nominal current of the load Z. The life of the wires (or cables) depends on the wire temperature. Figure 5 A and Figure 5B is a diagram showing a family of characteristic curves, each of which is a function of the maximum temperature difference dT (the highest temperature above the ambient temperature) and the cable cross section (e.g. in mm). 2 Each characteristic curve represents the relationship between the current and the maximum permissible time period that the conductor can carry the current without exceeding the maximum temperature difference. Figure 5 A includes various temperature differences dT and 0.35mm 2 The characteristic curve for a specific cross-sectional area is Figure 5 B includes characteristic curves for a specific temperature difference dT of 25K (Kelvin) and various cross-sectional areas. Figure 5 A and Figure 5 B shows that the cross-sectional area is 0.35mm 2 A wire can carry a current of about 9A (amperes) for an almost infinite time without exceeding a temperature difference dT of 25K above the ambient temperature. Figure 5 B shows that the cross-sectional area is 0.75 mm 2 A wire can carry a current of 10A (amperes) for approximately 100 seconds before exceeding a temperature difference dT of 25K above ambient temperature. In general, the greater the current, the shorter the permissible time period for a given cross-sectional area and a given temperature difference. It should be noted that Figure 5 A and Figure 5 The characteristic curve shown in the diagram of B has a linearly decreasing branch represented in double logarithmic form.

[0033] from Figure 5 A and Figure 5 B It can be seen that the temperature difference dT x (e.g., temperature values ​​dT1, dT2, dT3, dT4, dT5, dT6) and a given current (see Figure 5 A, current i x ) with a given integration time t x (e.g., time t1, t2, t3, t4, t5, t6) and a specific cross-sectional area (e.g., at Figure 5 In the example of A, it is 0.35 mm 2 ). Therefore, we can calculate the current i through the wire by L =i x The temperature value dT of a specific conductor cross section (which represents a temperature higher than the ambient temperature) is determined by integrating over time, and the first protection signal OC may indicate when the temperature value dT reaches a defined first reference temperature difference dT R The mentioned integration can be used to include the monitoring circuit 4 (see Figure 2 ) to effectively implement it. Figure 6 An exemplary implementation of a monitoring circuit is shown.

[0034] basically, Figure 6 The monitoring circuit is configured to determine the first protection signal OC based on the current sensing signal CS. As mentioned, the integration can be done in the digital filter 42 with an integration characteristic. According to the depicted example, the current sensing signal CS (which can be related to the load current i L The current sense signal CS is proportional to the current sense signal CS. The current sense signal CS is supplied to the input of a filter 45 which may be an (optional) analog low pass filter to remove transients etc. having a relatively high frequency and / or to perform an anti-aliasing filter function. The output of the filter 45 may be connected to the input of an analog to digital converter (ADC) 41 which is configured to digitize the filtered current sense signal CS. The ADC 41 may have a logarithmic characteristic in order to take into account Figure 5 A and Figure 5 B shows the logarithmic characteristic curve. Then, the (eg, logarithmic) digital current sensing signal CS DIG The resulting temperature value dT (which represents the temperature difference above the ambient temperature) is then supplied to a digital comparator 43, which may be configured to detect a temperature difference dT when the temperature value dT provided at the output of the digital filter 42 exceeds a first reference temperature difference dT specified for a particular conductor cross section. R (eg, 25K), the first protection signal OC is set to a high level. It should be noted that if ADC41 does not have a logarithmic characteristic, the digital current sensing signal CS DIG should be squared before being supplied to filter 42. In this regard, reference Figure 8 And publication US20170294772A1, in which this concept of temperature calculation is described.

[0035] As mentioned, the digital filter 42 is configured to convert the digitized current sense signal CS DIG Represents) load current i L and the associated integration time during which the current passes through the conductor. In this example, the filter characteristic 42 depends on parameters characterizing the conductor, such as the cross-sectional area of ​​the conductor, which carries the load current and can be represented by a family of characteristic curves, such as Figure 5 A shown in the figure (0.35mm 2 In one specific example, the characteristic curve (or related curve) can be stored as a lookup table, that is, by storing multiple sampling points of the characteristic curve in a memory. The value between two sampling points can be determined using, for example, interpolation.

[0036] Conventional fuses (slow-blow fuses, medium-blow fuses, fast-blow fuses) are produced for a specific trigger current and have a specific trigger time, where the trigger time corresponds to a reference temperature dT R and the specific combination of conductor cross-section A as described above (see Figure 5 A and Figure 5 B) However, it is desirable to have a configurable fuse that can be used for various wire parameters, such as, for example, wire cross section and reference temperature value dT R (maximum temperature above ambient temperature).

[0037] Figure 7 One example of an electronic fuse circuit, also referred to as a smart fuse circuit 10 , is shown. Figure 7 The circuit and Figure 2 The circuits of the logic circuit 3 are basically the same and reference is made to the corresponding description. However, the logic circuit 3 is Figure 2 The example is more complex, and the monitoring circuit 4 can be, for example, based on Figure 6 implementation, in which the analog low-pass filter 45 is omitted (the low-pass filter 45 is optional). However, with Figure 6 In this example, the monitoring circuit 4 can be configured such that its characteristics can be selected based on at least one conductor parameter, which for example allows the selection of a specific conductor cross section and / or a desired reference temperature difference dT R The characteristic curve (see Figure 5 ). In the examples described herein, at least one conductor parameter is or represents the cable cross-sectional area and / or the maximum temperature value above the ambient temperature or both. Figure 5 As can be seen in the figure, these two conductor parameters define a specific characteristic curve that represents the desired characteristics of the electronic fuse circuit for a specific conductor / cable. It should be understood that other parameters such as conductor diameter or absolute temperature (for example, in the case of measuring ambient temperature) can be used as conductor parameters. Furthermore, the conductor parameter does not have to be proportional to any physical quantity (such as cross-sectional area or temperature), but may simply be a numerical parameter that allows the desired characteristic curve used by the monitoring circuit to be determined (for example, selected) from a set of characteristic curves (see Figure 5 ).like Figure 7 As shown, the electronic fuse circuit can be an integrated circuit arranged in a chip package, wherein the electronic switch 2 and the remaining circuit components (driver 5, logic circuit 3 and monitoring circuit 4) can be integrated in the same semiconductor die or integrated in two separate semiconductor dies arranged in the chip package. However, in other embodiments, the smart fuse circuit 10 can be distributed in two or more separate chip packages. Figure 7 In the example shown, all depicted circuit components are integrated into one semiconductor chip.

[0038] The load current path of the electronic switch 2 can be connected between the power pin SUP and the output pin OUT of the smart fuse circuit 10. Generally, the logic circuit 3 can be configured to receive at least one wire parameter, which in this example includes the wire cross-sectional area A and the reference temperature difference dT from the microcontroller or other control circuit system. R Information. Figure 6 As shown, the logic circuit 3 can be configured to receive an input signal S IN , see also Figure 2 ) and (select signal S S1 and S S2 Represented by) input pin SEL T and SEL C Receives a signal from the controller and provides a drive signal S for the electronic switch 2 ON In this example, the signal S is selected S1 Indicates a specific curve in a set of specific curves, and therefore represents the wire parameter. The selection signal S S2 indicates a specific trip current representing the maximum current i for triggering an overcurrent shutdown (eg, implemented using comparator 6). TRIP (trip current). The driver 5 may be configured to convert the signal S as a binary logic signal ON Converted into a driving voltage V suitable for turning on and off the electronic switch 2 GS (gate-source voltage) or the corresponding drive current. Figure 2 As in the example of FIG. 4 , the monitoring circuit 4 receives the (analog) current sensing signal CS and generates a first protection signal OC based on the current sensing signal CS which can be processed by the logic circuit 3, for example, as Figure 3 as shown in the example.

[0039] Based on information included in at least one conductor parameter and received, for example, from a controller, the control logic 3 may configure the digital filter 42 and / or the comparator 43 so that the characteristics of the monitoring circuit 4 correspond to the conductor cross-sectional area A and the reference temperature difference dT R In this example, the monitoring circuit 4 can be based on the input pin SEL T The selection signal S received at S1 Therefore, the signal S S1 Parameters indicating the desired conductor (cross section and temperature difference) can be represented. Figure 4The ground pin GND shown is coupled to a reference potential, e.g., ground potential, and is connected to the logic circuit 3 and other circuit components that require a reference potential to function properly. It should be understood that in another embodiment, the (multiple) conductor parameters can also be encoded as a single (e.g., digital) selection signal, for example, received by a digital communication interface such as a serial peripheral interface (SPI). Further, it should be understood that the specific mechanism of how the relevant information is provided to the logic circuit is not relevant. Basically, the monitoring circuit 4 is configured to be suitable for a specific conductor.

[0040] The comparator 6 mentioned above can be used to implement an additional protection mechanism, which responds to the detection of the load current i L Equal to or greater than the maximum current (i L ≥i TRIP ) to initiate an immediate over-current shutdown, which can be based on the input pin SEL C The selection signal S received at S2 Thus, the comparator 6 responds to the detection of the i by setting the second protection signal OC2 to an appropriate logic level (eg, a high level). L ≥i TRIP The logic circuit 3 is signaled to trigger an immediate overcurrent shutdown. It should be noted that this additional protection mechanism is independent of the selected characteristic curve and is mainly intended to protect the electronic switch 2 itself rather than the load and the wire. In other embodiments, the maximum current / trip current i TRIP ) can be provided to the logic circuit, for example, via a serial communication interface (such as the SPI mentioned above).

[0041] Figure 8 Another exemplary embodiment of the monitoring circuit 4 is shown in more detail. Figure 8 An example of how current sensing can be implemented in more detail is also shown. For current measurement, a so-called Sense-FET circuit is used. That is, the electronic switch actually comprises two MOSFET transistors 21 and 22; transistor 21 is the actual load transistor coupled between the power supply node (power supply pin SUP) and the output node (output pin OUT) and carries the load current i L , and transistor 22 is configured to provide a sensing current i CS1 The sensing transistor, which senses the current i CS1 Indicates load current i L The gates of the load transistor 21 and the sense transistor 22 are connected and receive the same gate voltage V G Likewise, the drains of the load transistor 21 and the sense transistor 22 are connected and receive the same drain voltage (the power supply voltage V in the case of a high-side configuration).B ). The source current of the sensing transistor is called the sensing current i CS1 When the drain-source voltages of the two transistors 21 and 22 are equal, the source current is equal to the load current i L (the source current of the load transistor 21) is substantially proportional. In this case, the two transistors operate in the same operating point, and the ratio of the source current i L / i CS1 Equal to the ratio A of the active areas of transistors 21 and 22 21 / A 22 .

[0042] Figure 8 The monitoring circuit 4 receives a current sensing signal from the current sensing circuit, which is a digital signal CS in this example. DIG The current sensing circuit basically comprises a source current i CS1 The sensing transistor 33 (sensing current) and the analog-to-digital converter. According to the present example, the analog-to-digital converter (ADC) 41 may be a counter-type ADC or a SAR (successive approximation register) type ADC. Thus, the ADC 41 includes a control circuit 411, a current output digital-to-analog converter (DAC) 412, and a comparator 413. The DAC 412 is basically a current source, which can be controlled by a digital control signal provided by a digital register CNT included in the control circuit 411. The control circuit 411 is configured to modify the digital register CNT according to a given scheme, and the resulting analog current i CS1 The output node of the current output DAC 412 is connected to the source of the sense transistor 22, and therefore, the source current of the sense transistor is actually set by the DAC 412. The comparator 413 is configured to compare the source potentials (drain-source voltages) of the load transistor 21 and the sense transistor 22, and indicates (by a change in the level of its output) when the source potentials are equal. In other words, the comparator 413 indicates when to sample the source current i of the sense transistor 22. CS1 As mentioned, in this case (transistors 21 and 22 have equal source potentials), the sense current i CS With the load current i L Therefore, the current value of register CNT represents the load current and serves as the digital current detection signal CS. DIG In a simple implementation, the control circuit 411 may essentially comprise a counter that is periodically reset and incremented (thereby ramping up the DAC output current) until the comparator 413 indicates that the source potentials of the transistors 21, 22 are equal. As mentioned, more complex schemes (such as SAR) may be used to modify the register CNT.

[0043] Depending on the implementation, the monitoring circuit 4 may (optionally) include a decimator 44 to reduce the data rate of the digital data stream provided by the ADC 41 or to provide an averaging function. The monitoring circuit 4 may also include a square unit 45 configured to calculate the digital current sensing signal CS DIG The square unit 45 is optional and, as already mentioned above, can be omitted when the ADC 41 has a logarithmic characteristic. Figure 8 In the depicted example, the ADC 41 has a linear characteristic and uses a digital filter 42 to square the current sensing signal CS. DIG 2 Filtering is performed. The filter 42 may include an integral characteristic as mentioned above, and the filter output signal represents the cable temperature and indicates the temperature difference dT of the cable above the ambient temperature. The digital comparator 43 is used to compare the temperature difference dT with a threshold value, and when the reference temperature difference dT is exceeded, the digital comparator 43 generates a signal. R When the overcurrent (signal OC) is reached, it indicates an overcurrent. It should be noted that the digital circuit system included in the monitoring circuit 4 operates using the clock signal CLK and needs to be initialized to a specific initial state, which is usually accomplished by the reset signal RES.

[0044] Fig. 9 Another exemplary implementation of the current sensing function is shown. Basically, Fig. 9 The current sensing circuit shown in FIG. 1 is discussed further above. Figure 8 The current sensing circuit included in the Fig. 9 In the example of FIG. 1 , a Sense-FET circuit is used, in which the electronic switch 2 includes three MOSFET transistors 21, 22 and 23. Transistor 21 is an actual load transistor coupled between the power supply node (power supply pin SUP) and the output node (output pin OUT), and carries the load current i L (like Figure 8 ); transistors 22 and 23 are both configured as sensing transistors, and when the transistors are operated at the same operating point (ie, equal gate potential, drain potential, and source potential), these sensing transistors respectively provide an indication of the load current i L The sensing current i CS1 and i CS2 The gate of the load transistor 21 is connected to the gates of the sense transistors 22 and 23 and receives the same gate voltage V G Likewise, the drain of load transistor 21 is connected to the drains of sense transistors 22 and 23 and receives the same drain voltage (the power supply voltage V in the case of a high-side configuration). B ). The source current of the sensing transistor 22 is referred to as the sensing current iCS1 , and the source current of the sensing transistor 23 is called the sensing current i CS2 , when the drain-source voltages of transistors 21, 22, and 23 are equal, both are connected to the load current i L (the source current of the load transistor 21).

[0045] Fig. 9 The components on the right side (current output DAC 412, control circuit 411, and comparator 413) are similar to Figure 8 The control circuit 411 can be used as an analog-to-digital converter and generate a digital current sensing signal CS DIG , the digital current sensing signal CS DIG For example, it is used to calculate the temperature difference dT in a monitoring circuit. Fig. 9 The components on the left (another transistor 232, resistor R CS , and amplifier 231) are configured to perform redundant current measurement. In this example, transistor 232 is a p-channel MOS transistor whose source is connected to the source of sensing transistor 23 so that the source current i of sensing transistor 23 is CS2 is also the source current of the other transistor 232. The first input and the second input of the amplifier 231 are connected to the sources of the load transistor 21 and the sense transistor 23, and the output of the amplifier 231 is connected to the gate of the transistor 232. The amplifier 232 can be implemented as an operational transconductance amplifier (OTA), which drives the transistor 232 so that the difference between the source potentials of the load transistor 21 and the sense transistor 23 is close to zero. As mentioned, in this case, when the two transistors 21, 23 are operated in the same operating point, the sense current i CS2 With the load current i L The sensing current i CS2 Through the resistor R CS , the resistor R CS is connected in series to the drain-source path of transistor 232. In the depicted example, resistor R CS Connected between the drain of transistor 232 and the ground potential. CS The voltage drop across the terminals is V CS (V CS =R CS ·i CS2 ) can be used as an analog current sensing signal and supplied to the Figure 7 The comparator 6 is shown. The comparator can be configured to convert the analog current detection signal V CS With reference voltage V REF =R CS ·i TRIP / k ILISIn this example, k ILIS is the load current i L With the sensing current i CS2 The proportional factor between CS2 =i L / k ILIS ), while i TRIP is the trip current for overcurrent shutdown (when condition i is detected L ≥i TRIP hour).

[0046] It should be noted that the analog current sensing signal V CS can be supplied to the comparator 6 (see Figure 7 ), which monitors the load current so that when the load current exceeds a certain maximum value, an over-current shutdown is triggered, and the digital current sensing signal CS can be processed in the monitoring circuit 4 DIG , in order to initiate the switching off of the electronic switch according to the preselected characteristic curve of the specific conductor. Additionally, information about the measured load current can also be provided to an external microcontroller 8 (see Figure 1 ) or other external circuits. To this end, the electronic fuse device may have a dedicated current output pin IS, at which a diagnostic current i S , the diagnostic current i S Carrying information such as measured load current, measured temperature, current parameter settings, etc. Additionally or alternatively, the electronic fuse may include a communication interface (comm.) such as SPI (Serial Peripheral Interface) configured to receive digital information representative of the load current (e.g., digital signal CS DIG ) and transfers that information to a digital communication link. In the case of an SPI link, four pins, MISO, MOSI, SCLK, and SS, are typically used. SPI is a well-known de facto standard, so it will not be described in detail in this article.

[0047] Fig.10 It shows that the analog sensing current i can be output at the pin IS CS2 (Analog current sensing signal, Figure 2 The output represents the digital current sensing signal CS DIG The sensing current i CS1 The output current can usually be referred to as the sense current i S , and through Fig.10 The resistor R shown S Discharge current i S To convert it into the corresponding voltage V S It should be understood that the resistor R SA component which is externally connected to the electronic fuse device at pin IS. However, the resistor can also be integrated in the electronic fuse device; in this case, pin IS provides a diagnostic voltage instead of a diagnostic current.

[0048] Fig.10 The circuit and Fig. 9 The circuits in are substantially the same and reference is made to the above description to avoid repetition. However, Fig.10 The circuit additionally comprises a current output circuit 9, which is configured to convert the sense current i CS1 Or the sensing current i CS2 The current output circuit 9 may include an analog multiplexer 91 configured to receive the sense current i CS1 and i CS2 , and directs a selected one of these currents to the output pin IS. The selection can be made according to the level of the selection signal ISOUT, which can be provided, for example, by the logic circuit 3 (see Figure 7 ) is generated. In the depicted example, the current output circuit 9 also includes an electronic switch 92. When the current i CS1 When not selected, the electronic switch 92 is closed, so that the current path is closed, and when the current i CS1 When unavailable, the current i CS1 In this example, the current output circuit 9 is configured to directly output the sense current i CS2 or CS1 It will be appreciated that in other examples, a current mirror may be used to provide a current equal to i CS1 or CS2 The mirror current of the current output circuit 9 is selected, and the mirror current can be output at the pin IS. For the function of the current output circuit 9, it is irrelevant whether the selected current is output directly or indirectly (eg, via a current mirror).

[0049] Fig.11 An example of Fig.10 Therefore, Fig.11 The circuit and Fig.10 The circuits in are substantially the same and reference is made to the above description to avoid repetition. However, Fig.11 The circuit includes an additional current source Q F , which is configured to provide a current i FAULT The current i FAULT is supplied to a current output circuit configured to output a current i at a pin IS in response to detecting, for example, erroneous operation of the current sensing circuit. FAULT .

[0050] exist Fig.11 In the present example, when the difference between the source potentials of the sensing transistors 22 and 23 is greater than the maximum allowable difference, erroneous operation of the current sensing circuit is detected. To this end, the current output circuit 9 may include a comparator 93 configured to detect when the source potential of the sensing transistor 22 differs from the source potential of the sensing transistor 23 by more than a specified amount. When such a deviation is detected, the current source Q F can be connected to a multiplexer 9, which in this example is implemented by an electronic switch 94, which is driven by the output of a comparator 93. When the switch 93 is closed, the current i FAULT The sense current i is injected into CS2 Therefore, as discussed above, when the comparator detects an erroneous operation of the current sensing circuit, the multiplexer receives the sum current i CS2 +i FAULT Instead of sensing the current i CS2 .

[0051] In other words, the current i FAULT When the detection current i CS2 and i CS1 When the inconsistency is added to the detection current i CS2 When the selection is made to sense the current i CS2 When the IS pin is output, the external circuit system connected to the IS pin may detect the offset current i FAULT , and obtain information about the detected inconsistency / erroneous operation. It should be understood that the current i FAULT does not need to be added to the sense current i CS2 Alternatively, the multiplexer 91 may be configured to output the offset current i FAULT ,i CS2 and CS1 When the inconsistency / error operation mentioned above is detected, select i FAULT .

[0052] Fig.12 Shows Fig.11 A slight modification of the example. Fig.12 The example is substantially the same as the previous example, and reference is made to the above description to avoid repetition. Fig.12 and Fig.11 In the implementation of the current output circuit 9 (especially in the control current i FAULT In essence, the method used for Fig.11 The voltage comparator 93 of the example is Fig.12 Thus, the current comparator 93' is configured to detect when the current i CS1With current i CS2 The current comparator 93' has the characteristics of a window comparator. In other words, the current comparator 93' can use two threshold values ​​i TH1 and i TH2 , that is, for example, i TH1 =i CS2 (1-x / 100) and i TH2 =i CS2 (1+x / 100), where x represents a predetermined percentage. At its output, the current comparator 93' will indicate whether the condition i is violated. TH1 CS1 TH2 (i.e. i CS1 Is it related to i CS2 If this is the case, switch 94 will close and current i FAULT As an offset current added to i CS2 , as mentioned above Fig.11 Explained.

[0053] exist Fig.13 In the example of FIG. 1 , a practical implementation of the current comparator 93 ′ is shown, wherein the current comparator is implemented using a current mirror. Fig.13 The rest of Fig.12 Basically the same, so the following description focuses on the current comparator. In order to realize the two thresholds i TH1 and i TH2 , providing a first current mirror, which is composed of transistors 301, 302 and 303. Transistor 301 forms the input transistor of the current mirror, that is, the source-drain current path of transistor 301 is connected in series to the source-drain current path of transistor 232. Transistors 302 and 303 form two output transistors of the current mirror and provide two mirror currents i CS2 'and i CS2 The current mirror can be designed so that the ratio i CS2 ' / i CS2 is 1-x / 100 and the ratio i CS2 ” / i CS2 =1+x. / 100, where x corresponds to the predetermined percentage mentioned above. The two output transistors 302 and 303 of the current mirror are connected in series to current sources 412' and 412", respectively, both of which are controllable current sources that are controlled to discharge the same current as the current source 412 (current output DAC). Therefore, the current sources 412, 412' and 412" can also be regarded as current mirrors. It should be noted that i CS2 'and i CS2 ​​” corresponds to the threshold current i mentioned in the previous example TH1 and i TH2 .

[0054] In normal operation (i.e., when i CS2 ' CS1 CS2 ”), the potential of the common circuit node N′ of the current source 412′ and the transistor 302 will be pulled down (towards ground), and the potential of the common circuit node N″ of the current source 412″ and the transistor 303 will be pulled up (towards the power supply voltage V B ) pull up. CS2 ' CS2 ”≤i CS1 In the effective case, the potentials of the two circuit nodes N' and N" will be pulled down. Similarly, in i CS1 ≤i CS2 ' CS2 In the case where "is valid, the potentials of the circuit nodes N' and N" will be pulled up. Therefore, the potential difference between the circuit nodes N' and N" will only be CS2 ' CS1 CS2 " reaches a significant value. The comparator 93" is configured to detect when the potential difference between the circuit nodes N' and N" drops to a low value, that is, to detect when the normal operating condition i is violated. CS2 ' CS1 CS2 If this is the case, switch 94 is closed as in the previous example, causing the offset current i FAULT Added to the sense current i CS2 .

[0055] Fig.14 An exemplary embodiment of how to use an electronic fuse circuit 10 (smart fuse circuit) to protect a load is shown. In particular, Fig.14 The circuit system includes circuits connected to the electronic fuse circuit 10 from the outside, which is integrated in a single chip in this example. The power supply pin SUP is connected to a power supply (eg, providing a power supply voltage V B The input signal S supplied to the input pin IN is IN is a logic signal whose logic level (high level or low level) indicates whether the electronic switch 2 is turned on or off. The load (represented by the impedance Z) is connected to the output pin OUT via a wire. The selection signal S mentioned above S1 and S S2 The resistor R T and R C Connect to the input pin SEL​​​​​​​​T and SEL C to generate (see also Figure 7 The electronic fuse circuit may include a current source at an input pin SEL T and SEL C The input pin provides a limited constant current i T and i C These currents i T and i C Connect to the input pin SEL via T and SEL C The resistor R T and R C discharge, resulting in a corresponding voltage drop i T ·R T and i C ·R C These voltage drops form Figure 7 The selection signal S mentioned in the example shown in S1 and S S2 , and represent the desired wire characteristics to be selected ( Figure 5 ) and the expected maximum current i to be used by the overcurrent shutdown function mentioned above TRIP The signal S received on the input pin DEN (Diagnosis ENable pin) DEN Can be used to control the information output at the current output pin IS.

[0056] Fig.15 The timing diagram of FIG. 1 shows an example of a diagnostic function which can be implemented (in particular) in the logic circuit 3 and allows an external controller (see, for example, Figure 1 , the microcontroller 8) reads diagnostic information, such as the sensed current i CS1 or CS2 Or other parameters. When the input signal S DEN When the diagnostic request signal (“Diagnosis ENable”) is set to a high level, for example, a diagnostic current i is output at the pin IS. S The diagnostic current i S The meaning (i.e., the diagnostic current i S The information conveyed) depends on the input signal S IN The logic level and signal S DEN The timing of the high level pulse. Fig.15 In the example, the input signal S IN and S DEN And the diagnostic current i S An exemplary timing diagram of .

[0057] When the input signal SIN When at a high level, this high level indicates that the electronic switch 2 is turned on (normal operation), and the high level of the diagnostic request signal S DEN will cause a diagnostic current i S , and this diagnostic current i S indicates the load current i L . That is to say, the multiplexer 91 (see Figures 10 to 13 ) is controlled such that its output analog current sensing signal i CS2 . As can be seen from Fig.15 , if after the diagnostic request signal S DEN has been at a low level for at least one given time period T0 (pulse pause time), a rising edge appears in the diagnostic request signal S DEN , then the high level of the diagnostic request signal S DEN makes the diagnostic current i S = i CS2 indicate the load current i L .

[0058] If the diagnostic request signal S DEN includes two or more "on pulses", and the (multiple) pauses between the on pulses are shorter than the time period T0, then other information (in addition to the sensed current i CS2 ) can be read out. In the example of Fig.15 , the third on pulse in the diagnostic request signal S DEN (the second timing diagram of Fig.15 ) follows the second on pulse, where the pause is shorter than T0 (pause time T P < T0), so the diagnostic current i S output at the pin IS is set to indicate the sensed current i CS1 provided by the current output DAC412 (see Figures 10 to 13 ). Similarly, after a pause shorter than the given time period T0, the fourth (last) on pulse in the diagnostic request signal S DEN is also asserted, so the diagnostic current i S output at the pin IS is set to indicate the currently used trip current i Figure 7 for triggering overcurrent shutdown (comparator 6, see TRIP ).

[0059] In summary, generally, the diagnostic current is controlled according to the pulse pattern of the diagnostic request signal S DEN so that the current output circuit sets the value of the diagnostic current i S such that it represents the load current (current sensing signal i CS2 , i CS1 , etc.), the trip current i TRIP , etc.

[0060] Although the present invention has been shown and described with respect to one or more implementations, changes and / or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. With particular regard to the various functions performed by the components or structures (units, components, devices, circuits, systems, etc.) described above, the terms used to describe these components (including references to "devices") are intended to correspond to any component or structure that performs the specified function of the described component (e.g., which is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs that function in the exemplary implementations of the invention shown herein, unless otherwise indicated.

Claims

1. An integrated circuit, comprising: A transistor (21) coupled between a power supply pin (SUP) and an output pin (OUT); The current output circuit (9) is configured to provide a diagnostic current (i S ); A current sensing circuit is coupled to the transistor (21) and is configured to generate a first current sensing signal (i CS1 ) and the second current sensing signal (i CS2 ), the first current sensing signal (i CS1 ) indicates the load current passing through the transistor (21), the second current sensing signal (i CS2 ) indicates the load current; A comparator circuit is configured to detect the first current sensing signal (i CS1 ) and the second current sensing signal (i CS2 ) are consistent; as well as A current source provides another current (i FAULT ); The current output circuit (9) is configured to select one of the following as the diagnostic current according to the control signal (ISOUT): the first current sensing signal (I CS1 ) and the second current sensing signal (i CS2 ), wherein the current output circuit (9) is configured to respond to the comparator circuit detecting the first current sensing signal (i CS1 ) and the second current sensing signal (i CS2 ) is inconsistent and outputs the other current (i FAULT ), and wherein the other current (i FAULT ) is superimposed on the first current sensing signal (i CS1 ) or the second current sensing signal (i CS2 ) on the offset current.

2. The integrated circuit according to claim 1, The current sensing circuit includes an analog circuit system and a digital circuit system, and the first current sensing signal (i CS1 ) is generated using a digital circuit system, and the second current sensing signal (i CS2 ) was generated using only analog circuitry.

3. The integrated circuit according to claim 2, wherein the digital circuitry of the current sensing circuit is configured to provide digital information indicative of the load current (CS DIG ),as well as Wherein the integrated circuit includes a digital communication interface configured to receive the digital information and configured to transmit the digital information across a digital communication link.

4. The integrated circuit according to claim 1, The current sensing circuit comprises a first sensing transistor (22) and a second sensing transistor (23) coupled to the transistor (21), the current passing through the first sensing transistor (22) being the first current sensing signal (i CS1 ), and the current through the second sensing transistor (23) is the second current sensing signal (i CS2 ).

5. The integrated circuit according to claim 4, wherein the current sensing circuit comprises a digital-to-analog converter (412) coupled to the first sensing transistor (22) and configured to set the current through the first sensing transistor (22) according to a digital signal; and The current sensing circuit comprises a control circuit (411) configured to modify the digital signal so that the first sensing transistor (22) and the transistor (21) operate at approximately the same operating point.

6. An integrated circuit according to claim 4 or 5, The current sensing circuit comprises a further transistor (232) having a main current path which is serially coupled to the main current path of the second sensing transistor (23), and the current sensing circuit further comprises an amplifier (231) which is configured to drive the transistor (232) such that a voltage drop across the main current path of the transistor is substantially equal to a voltage drop across the main current path of the second sensing transistor (23).

7. The integrated circuit of claim 1 , further comprising: Input pin (DEN) for receiving diagnostic signals (S DEN ), wherein the control signal for determining the diagnostic current to be selected depends on the diagnostic signal (S DEN ) pulse mode.

8. The integrated circuit of claim 1 , further comprising: A monitoring circuit (4) is configured to detect the current flow of the first current sensing signal (i CS1 ) and a preset time-temperature characteristic associated with a wire connected to the output pin (OUT) to generate a protection signal (OC).

9. A method comprising: establishing a load current path between a power supply pin (SUP) and an output pin (OUT) by activating a transistor (21); A first current sensing signal (i CS1 ) and the second current sensing signal (i CS2 ), the first current sensing signal (i CS1 ) indicates the load current passing through the transistor (21), the second current sensing signal (i CS2 ) indicates the load current; Detecting, via a comparator circuit, whether the first current sensing signal is consistent with the second current sensing signal; providing, via a current source, another current indicative of the error; Through the current output circuit and according to the control signal (ISOUT), one of the following signals is selected as the diagnostic current: the first current sensing signal (i CS1 ) and the second current sensing signal (i CS2 ); The selected signal is provided as the diagnostic current (i S ); as well as The other current is output via the current output circuit in response to the comparator circuit detecting that the first current sensing signal and the second current sensing signal are inconsistent, and wherein the other current is an offset current superimposed on the first current sensing signal or the second current sensing signal.

10. The method according to claim 9, further comprising: Based on the first current sensing signal (i CS1 ) and a preset time-temperature characteristic associated with a wire connected to the output pin (OUT) to generate a protection signal (OC), The power supply pin (SUP) is disconnected from the output pin (OUT) by disabling a transistor (21) in response to the protection signal (OC).

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