Bidirectional integrated current sensor with low temperature coefficient

Abstract

This disclosure describes various bidirectional current sensing techniques. The described solution uses a tuned thermal substrate, e.g., copper, in conjunction with the front two amplifiers of a three-amplifier instrumentation amplifier. The described bidirectional system current sensor module uses the tuned thermal substrate approach to eliminate the dependence on the temperature coefficient in the sensor. The circuitry after the front two amplifiers can be varied to support factory gain trimming and voltage or current mode outputs.

Description

AREA OF REVELATION

[0001] This document refers generally, but not by way of limitation, to an electrical current sensor and more specifically, but not by way of limitation, to a laminate-based current sensor with "zero" temperature coefficients. BACKGROUND

[0002] The sensing of large currents on a printed circuit board (PCB), such as those found at the 12 V DC input of a server or network switch, may require the use of a sensing element that can safely conduct large currents with minimal power dissipation. To sense input currents above 100 amperes, a sensing element resistance on the order of 150 µΩ or less may be required. Such a sensing element can be in the form of a discrete sensing resistor, which may, for example, be soldered to the PCB, or even a resistor formed by the resistance of a PCB trace itself. The voltage developed across the sensing resistor can be measured using various techniques, such as an analog-to-digital converter (ADC) in the system, which can be further conditioned or signal processed to produce a value that represents the sensed current (e.g.,in amperes), which represents the current through the sensing element.

[0003] Discrete sense resistors with low temperature coefficients are typically made from exotic materials such as iron-chromium or manganese-copper alloys. These exotic materials can achieve a low temperature coefficient of resistance (TCR), but can be expensive. Accurately sensing the voltage across such a sense resistor element can also be difficult, given the large current (leading to ohmic "IR" voltage drops on the circuit board) and the small voltage drop across the sense resistor used as the current sensing element, which is required to maintain reasonable power dissipation in the sense resistor. Some Kelvin sense resistors are available that may have sensing points integrated into the sense resistor, but these are typically even more expensive.

[0004] Another way to sense large currents is to use a section of a copper trace on a printed circuit board (PCB) itself as the current sensing element. This has the advantage that the PCB trace is already present on the board, eliminating the need to introduce additional voltage drops (e.g., due to a discrete sensing element). However, copper has a high TCR (3900 ppm / °C). Thus, as the temperature of the PCB changes, either due to changes in the ambient temperature or due to power dissipation of the IR drop across the copper trace, the absolute resistance of the sensing element changes.Although this effect can be compensated for, for example, by using a temperature sensor near the sensing element and some analog or digital signal conditioning in the measurement circuitry, such temperature compensation involves additional complexity.

[0005] Furthermore, the accuracy of a discrete current-sensing resistor or the thickness and width of the PCB trace may not be sufficiently controlled to achieve the desired final system accuracy. Trimming techniques can be applied to the final PCB assembly, but this adds cost and testing complexity to the PCB manufacturing process, assuming the current can be measured externally or applied accurately enough to achieve the desired trimming target. SUMMARY OF REVELATION

[0006] This disclosure describes various bidirectional current sensing methods. The solution described in this disclosure uses a tuned thermal substrate, e.g., copper, in conjunction with the front two amplifiers of a three-amplifier instrumentation amplifier. The described bidirectional system current sensor module uses the tuned thermal substrate approach to eliminate the temperature coefficient dependence in the sensor. Behind the front two amplifiers, the circuitry can be varied to support factory gain trimming and voltage or current mode outputs.

[0007] In some aspects, this disclosure relates to a bidirectional system current sensor module comprising: an input node, a first output node, a second output node, and a system current monitoring node; a first output transistor coupled between the input node and the first output node; a second output transistor coupled between the system current monitoring node and the second output node; a first resistor coupled between the input node and the system current monitoring node; a second resistor coupled between the input node and the first output transistor; a third resistor coupled between the system current monitoring node and the second output transistor;a first amplifier including a first amplifier input coupled to the second resistor, a second amplifier input coupled to an output node of a first trim circuit, and an amplifier output coupled to a control node of the first output transistor; and a second amplifier including a first amplifier input coupled to the third resistor, a second amplifier input coupled to an output node of a second trim circuit, and an amplifier output coupled to a control node of the second output transistor, wherein the first output node and the second output node are configured to generate a differential output monitor current.

[0008] In some aspects, this disclosure relates to a method for sensing or measuring a bidirectional system load current, comprising: in response to a system load current flowing in a first direction between an input node and a system current monitoring node via a first resistor, shunting a first output monitoring current across a second resistor; adjusting, using a first trimming circuit coupled across and in parallel with the first resistor, a gain between the input node and the system current monitoring node; and controlling, using a first amplifier configured in a closed feedback loop, the first output monitoring current such that a voltage difference at a first and a second input of the first amplifier tends to be reduced or minimized;and in response to the system load current flowing in a direction opposite to the first direction between the input node and the system current monitoring node via the first resistor, shunting a second output monitoring current across a third resistor; adjusting, using a second trimming circuit coupled across and in parallel with the first resistor, a signal between the input node and the system current monitoring node; and controlling, using a second amplifier configured in a closed feedback loop, the second output monitoring current such that a voltage difference at a first and a second input of the second amplifier tends to be reduced or minimized.

[0009] In some aspects, this disclosure relates to a bidirectional system current sensor module comprising: an input node, a first output node, a second output node, and a system current monitoring node; a first resistor coupled between the input node and the system current monitoring node, the first resistor having a first node and a second node; a first output transistor coupled between the system current monitoring node and the first output node; a second output transistor coupled between the system current monitoring node and the second output node; a second resistor coupled between the first output transistor and the second output transistor;and a first amplifier comprising: a first amplifier input coupled to an output node of a first trimming circuit, and a first amplifier output coupled to a control node of the first output transistor; a second amplifier input coupled to an output node of a second trimming circuit, and a second amplifier output coupled to a control node of the second output transistor, wherein the first output node and the second output node are configured to generate a differential output monitoring current. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, which are not necessarily drawn to scale, like numbers may describe similar components in different views. Like numbers with different suffixes may represent different instances of similar components. The drawings generally illustrate, by way of example but not limitation, various embodiments discussed in this document. Fig. 1 shows an example architecture of a system current sensor module. Fig. Figure 2 shows an example of a linear system current sensor module architecture. Fig. 3 shows an example of a linear bidirectional system current sensor module architecture using various techniques of this disclosure. Fig. 4 shows another example of a bidirectional system current sensor module architecture utilizing various techniques of this disclosure. Fig. 5 shows another example of a bidirectional system current sensor module architecture utilizing various techniques of this disclosure. Fig. 6 is a flowchart of an example method for sensing or measuring a bidirectional system load current. DETAILED DESCRIPTION

[0011] Conventional current sensor control loops use a gain trim term in the denominator. The present inventors have recognized that the gain trim term in the denominator creates a nonlinear relationship with respect to the trim code. This nonlinear relationship requires high-resolution digital-to-analog converters (DACs) to fine-tune the gain adjustment. High-resolution DACs increase cost and power consumption.

[0012] The present inventors have discovered that by moving the gain trim term from the denominator to the numerator, a linear relationship is created with respect to the trim code. This linear relationship reduces the dynamic range required by the DAC, allowing the use of low-resolution DACs to smoothly adjust the gain while maintaining stability and accuracy.

[0013] Furthermore, the inventors of the present invention recognized the desirability of a system current sensor module with bidirectional capabilities. Bidirectional current sensing is typically implemented using an instrumentation amplifier with a single current sense resistor. However, a single current sense resistor for high current typically exhibits poor temperature coefficient performance and poor process variation. The solution described in this disclosure uses a tuned thermal substrate, e.g., copper, in conjunction with the front two amplifiers of a three-amplifier instrumentation amplifier. The described bidirectional system current sensor module uses the tuned thermal substrate approach to eliminate the temperature coefficient dependence in the sensor.Behind the front two amplifiers, the circuitry can be varied to support factory gain trimming and voltage or current mode outputs.

[0014] Fig. 1 shows an example of an architecture of a system current sensor module 100. The system current sensor module 100 includes an input node 102 for receiving an input voltage VIN, a system current monitoring node 104 at which an output monitoring current ISENSE can be monitored, and an output node 106 at which an output monitoring current IOUTP is generated.

[0015] A resistive current sensing element RS between the input node 102 and the system current monitoring node 104, having a resistance of approximately 150 µΩ, for example, can serve as the primary current sensing element. The large "system load current" 124 from the system flows through this current sensing resistor RS.

[0016] Resistive gain adjustment elements R1 (e.g., 3.19 Ω) and R2 (e.g., 0.8 Ω) are connected in series between the input node 102 and the output transistor 108. As shown in Fig. As can be seen in Figure 1, a trim circuit 110 is coupled in parallel with resistive element R2. Trim circuit 110 is configured to receive a trim code via a trim code input 120 and, in response, to modify a voltage dependent on the VIN voltage at node 124, the resistive gain adjustment elements R1 and R2, and the sensor output current flow through transistor 114.

[0017] The output 122 of the trimming circuit 110 is coupled to a non-inverting input (first input 116) of the amplifier 112. The system current monitoring node 104 is coupled to the inverting input (second input 118) of the amplifier 112. The output of the amplifier 112 is coupled to a control node 114 of the output transistor 108, e.g., a gate terminal of a field-effect transistor (FET). The amplifier 112 is configured in a closed feedback loop to control the output current IOUTP such that a voltage difference between the first input 116 and the second input 118 of the amplifier 112 tends to be reduced or minimized.

[0018] The output monitoring current IOUTP of the system current sensor module 100 is given by Equation 1: IOUTP=(IIN*RS) / (R1+AV*R2) where IOUTP is the output monitor current, IIN is the system load current, RS is the resistance of the resistive element RS, R1 is the resistance of the resistive element R1, AV is the gain trim term, and R2 is the resistance of the resistive element R2.

[0019] As can be seen in Equation 1, the gain trimming term AV is located in the denominator, creating a nonlinear gain relationship between IIN and IOUTP. This nonlinear relationship complicates the trimming algorithm because small changes in the error have a large impact on the adjustment gain when the error is small, but a smaller impact when the error is large. This can require very high-resolution DACs to smoothly adjust the gain.

[0020] The inventors of the present invention have recognized that it is desirable for the gain trim term to be in the numerator of the equation, resulting in a linear relationship that can reduce or minimize the required trim resolution.

[0021] Fig. 2 shows an example of an architecture of a linear system current sensor module 200. The system current sensor module 200 includes an input node 202 for receiving an input voltage VIN, a system current monitoring node 204 at which an output monitoring current ISENSE can be monitored, and an output node 206 at which an output monitoring current IOUTP is generated.

[0022] A resistive current sensing element RS between the input node 202 and the system current monitoring node 204, having a resistance of approximately 150 µΩ, for example, can serve as the primary current sensing element. The large "system load current" 224 from the system flows through this current sensing resistor RS.

[0023] A resistive gain adjustment element R1 (e.g., 3.19 Ω) is connected in series between the input node 202 and the output transistor 208. In contrast to the system current sensor module 100 in Fig. 1, a trimming circuit 210 is coupled in parallel with the resistive element RS. The resistive element RS has a first node 226 and a second node 228, and the trimming circuit 210 is coupled to the first node 226 and the second node 228.

[0024] Trim circuit 210 is configured to receive a trim code ("TRIM") via a trim code input 212 and, in response, modify a voltage between input node 202 and system current monitoring node 204. For example, trim circuit 210 may couple a resistor corresponding to the trim code in parallel with resistive element RS to adjust the trim gain between a system load current 224 and an output monitoring current.

[0025] Furthermore, using the techniques of this disclosure, the resistive element R2 of Fig. 1 is removed, simplifying the resistor network. Using these techniques, the gain term is now in the numerator of the equation, resulting in a linear relationship that can reduce or minimize the required trimming resolution.

[0026] The output monitoring current IOUTP of the system current sensor module 200 is given by Equation 2: IOUTP=(IIN*RS*AV) / R1 where IOUTP is the output monitor current, IIN is the system load current, RS is the resistance of the resistive element RS, R1 is the resistance of the resistive element R1, and AV is the gain trim term.

[0027] The output 214 of the trimming circuit 210 is coupled to a non-inverting input (first input 216) of the amplifier 220. The source of the transistor 208 and the node 211 of the resistor R1 are coupled to an inverting input (second input 218) of the amplifier 220. The output of the amplifier 220 is coupled to a control node 222 of the output transistor 208, e.g., a gate terminal of a FET. The amplifier 220 is configured in a closed feedback loop to control the output monitoring current IOUTP such that a voltage difference between the first input 216 and the second input 218 of the amplifier 220 tends to be reduced or minimized.

[0028] It may be helpful to keep the two resistors (e.g., resistive element RS and resistive element R1) at the same temperature to maintain stable gain over temperature and reduce errors due to aging. Since the greatest power dissipation occurs in resistive element RS (through which the full, large system current can flow), resistive element R1 can be designed to be thermally coupled to resistive element RS, so that both resistive elements RS and R1 are at approximately the same temperature and experience the same temperature swings. This may involve forming a "thermal cage" to keep resistive element RS and resistive element R1 at the same temperature.Thus, in some examples, resistive element RS and resistive element R1 are thermally coupled to maintain a temperature of the second resistive element at or near a temperature of the first resistive element when a system load current flows through and heats the first resistor. Further information can be found in commonly assigned U.S. Patent 11,378,595, entitled "Low temperature coefficient current sensor," by Michael D. Petersen et al., the entire contents of which are incorporated herein by reference.

[0029] In some examples, resistive element RS and resistive element R1 comprise the same material. For example, both resistive element RS and resistive element R1 may be copper.

[0030] In some examples, the trimming circuit 210 may include a digital-to-analog converter.

[0031] The inventors of the present invention have recognized that it is desirable to Fig. 2 shown linear system current sensor module as a bidirectional current sensor, as in Fig. 3 shown.

[0032] Fig. Figure 3 shows an example architecture of a linear bidirectional system current sensor module 300 utilizing various techniques of this disclosure. The bidirectional system current sensor module 300 includes an input node 302 for receiving an input voltage VIN, a system current monitoring node 304 at which an output monitoring current ISENSE can be monitored, a first output node 306, and a second output node 308.

[0033] A resistive current sensing element RS, e.g., a resistor, is located between the input node 302 and the system current monitoring node 304, having, e.g., a resistance of approximately 150 µΩ, and can serve as the primary current sensing element. The large system load current 310 from the system flows through this current sensing resistor RS.

[0034] A first resistive gain adjustment element R1 (e.g., 3.19 Ω), e.g., a resistor, is connected in series between the input node 302 and the first output transistor 312. The resistive element RS has a first node 314 and a second node 316. A first trimming circuit 318 is coupled to the first node 314 and the second node 316.

[0035] For a system load current flowing in a first direction, e.g., from input node 302 to system current monitoring node 304, the first output monitoring current IOUTP is shunted across resistor R1. The first trim circuit 318 is configured to receive a first trim code ("TRIMP") via a trim code input 320 and, in response, to modify a voltage between the input node 302 and the system current monitoring node 304. For example, the first trim circuit 318 may couple a resistor corresponding to the first trim code in parallel with the resistive element RS to adjust the gain between the system load current 310 and a first output monitoring current IOUTP.

[0036] The first output monitoring current IOUTP is given by equation 3: IOUTP=(IIN*RS*Avp) / R1 where IIN is the system load current 310, Avp is a forward current trim gain and is set with the first trim code TRIMP, RS is the value of the resistive element RS, R1 is the value of the resistive element R1 and IOUTP is 0 in the reverse current.

[0037] The output 322 of the first trimming circuit 318 is coupled to a non-inverting input (first amplifier input 324) of the amplifier 326. An inverting input (second input 327) of the amplifier 326 is coupled to a node 311 between the resistor R1 and the source terminal of the first output transistor 312. The output 328 of the amplifier 326 is coupled to a control node 330 of the first output transistor 312, e.g., a gate terminal of a FET. The amplifier 326 is configured in a closed feedback loop to control the first output monitoring current IOUTP such that a voltage difference between the first input 324 and the second input 327 of the amplifier 326 tends to be reduced or minimized.

[0038] So far, the description of the bidirectional system current sensor module 300 is similar to that of the unidirectional system current sensor module 200 of Fig. 2. To account for a system load current flowing in the opposite direction to the first direction, e.g., from the system current monitoring node 304 to the input node 302, the bidirectional system current sensor module 300 may include additional circuitry.

[0039] A second resistive gain adjustment element R1A (e.g., 3.19 Ω), e.g., a resistor, is coupled in series between the system current monitoring node 304 and the second output transistor 308. A second output monitoring current IOUTM is shunted across the resistor R1A. Like the first trim circuit 318, a second trim circuit 332 is coupled to the first node 314 and the second node 316 of the resistive element RS. The second trim circuit 332 is configured to receive a second trim code ("TRIMM") via a trim code input 334 and, in response, to modify a voltage between the input node 302 and the system current monitoring node 304. For example, the second trimming circuit 332 may couple a resistor corresponding to the second trimming code in parallel with the resistive element RS to adjust the gain between the system load current 310 and the second output monitoring current IOUTM.

[0040] The second output monitoring current IOUTM is given by equation 4: IOUTM=(IIN*RS*Avm) / R1A where IIN is the system load current 310, Avm is a reverse current trim gain and is set with the second trim code TRIMM, RS is the value of the resistive element RS, R1A is the value of the resistive element R1A and IOUTM is 0 in the forward current.

[0041] The output 336 of the second trimming circuit 332 is coupled to a non-inverting input (first amplifier input 338) of the amplifier 340. An inverting input (a second amplifier input 342) of the amplifier 340 is coupled to a node between the resistor R1A and the source terminal of the second output transistor 344, e.g., a FET. The output 346 of the amplifier 340 is coupled to a control node 348 of the second output transistor 344. The amplifier 340 is configured in a closed feedback loop to control the second output monitoring current IOUTM such that a voltage difference between the first amplifier input 338 and the second amplifier input 342 of the amplifier 340 tends to be reduced or minimized. In the bidirectional techniques of this disclosure, the first output node 306 and the second output node 308 are configured to generate a differential output monitoring current.

[0042] In some examples, each of the first trimming circuit 318 and the second trimming circuit 332 includes a corresponding digital-to-analog converter. In some examples, the digital-to-analog converter includes a digital-to-analog voltage converter, e.g., an R-2R digital-to-analog converter.

[0043] It may be helpful to keep the three resistors (e.g., resistive element RS, resistive element R1, and resistive element R1A) at the same temperature to maintain stable gain over temperature and reduce errors due to aging. Since the greatest power dissipation occurs in resistive element RS (through which the full, large system load current 310 can flow), resistive elements R1 and R1A can be designed to be thermally coupled to resistive element RS so that these three resistive elements RS, R1, and R1A are at approximately the same temperature and experience the same temperature variations. This may involve forming a "thermal cage" to keep resistive elements RS, R1, and R1A at the same temperature.Thus, in some examples, the first resistor RS, the second resistor R1, and the third resistor R1A are thermally coupled to maintain a temperature of the second resistor and the third resistor at or near a temperature of the first resistor when a system load current 310 flows through the first resistor and heats the first resistor. Further information can be found in commonly assigned U.S. Patent 11,378,595, entitled "Low temperature coefficient current sensor," by Michael D. Petersen et al., the entire contents of which are incorporated herein by reference.

[0044] In some examples, the resistive elements RS, R1, and R1A comprise the same material. For example, the resistive elements RS, R1, and R1A may all be copper.

[0045] Fig. Figure 4 shows another example of a bidirectional system current sensor module 400 architecture utilizing various techniques of this disclosure. The bidirectional system current sensor module 400 includes an input node 402 for receiving an input voltage VIN, a first output node 404, a second output node 406, and a system current monitoring node 408. The first output node 404 and the second output node 406 are configured to generate a differential output monitoring current.

[0046] A resistive current sensing element RS, e.g., a resistor, is located between the input node 402 and the system current monitoring node 408, having, e.g., a resistance of approximately 150 µΩ, and can serve as the primary current sensing element. The large system load current 410 from the system flows through this current sensing resistor RS.

[0047] The bidirectional system current sensor module 400 includes a first trim circuit 414 and a second trim circuit 416. A trim code TRIM is applied to both the first trim circuit 414 and the second trim circuit 416, and in response, the first trim circuit 414 and the second trim circuit 416 modify a voltage between the input node 402 and the system current monitoring node 408 to produce a voltage proportional to the system load current across resistor RS and the trim code when a trim represented by the trim code provides variable attenuation based on the trim code.

[0048] The first trimming circuit 414 is coupled to receive a voltage of the first input node 402 and a voltage at a node between a first node 418 and the second node 420 of the resistive element RS. The second trimming circuit 416 is coupled to receive the voltage at a node 422 between the first node 418 and the second node 420 and a voltage at the second node 420. For example, a resistor R3, e.g., 1 kΩ, and a resistor R4, e.g., 1 kΩ, are coupled in series, with the resistor RS being coupled in parallel with the series combination of resistors R3 and R4. Node 422 is a node between the resistors R3 and R4.

[0049] In the example shown, node 422 may be coupled to a first input, e.g., a non-inverting input, of an amplifier 424. A second input, e.g., an inverting input, of amplifier 424 may be connected to an output of amplifier 424 in a unity gain buffer configuration. Output 426 may be applied to both first trimming circuit 414 and second trimming circuit 416.

[0050] The bidirectional system current sensor module 400 includes an amplifier 428, e.g., a differential amplifier. An output 430 of the first trimming circuit 414 is coupled to a non-inverting input of the amplifier 428, and an output 432 of the second trimming circuit 416 is coupled to an inverting input of the amplifier 428.

[0051] A first output 434 of amplifier 428 is coupled to a first output transistor 412, e.g., a control node 438 of the first output transistor 412. A second output 436 of amplifier 428 is coupled to a second output transistor 440, e.g., a control node 442 of the second output transistor 440. The amplifier 428 is in a closed feedback loop configuration with a resistor R2 coupled to the non-inverting input and a resistor R5 coupled to the inverting input. Both resistors R2 and R5 may, for example, have a similar resistance of 2R, where R corresponds to the output resistance of an R2R digital-to-analog voltage converter. The first trimming circuit 414 and the second trimming circuit 416 may each comprise a corresponding digital-to-analog converter, e.g., a digital-to-analog converter. B. an R2R digital-to-analog voltage converter.

[0052] The bidirectional system current sensor module 400 may include a first current source 444 coupled in series with the first output transistor 412 and configured to source a first reference current IREF, and a second current source 446 coupled in series with the second output transistor 440 and configured to source a second reference current IREF. A gain adjustment resistor R1 may be coupled between the first output transistor 412 and the second output transistor 440.

[0053] In operation, the system's feedback drives amplifier input voltages 430 and 432 to nearly the same voltage, resulting in a voltage proportional to the difference VIN-ISENSE being applied across resistor R1. During trimming, VIN-ISENSE = Av*(BA), where Av is the gain, B is the voltage at node B, and A is the voltage at node A. When trimming is 1, VIN - ISENSE = B - A. Specifically, the voltage across R1 is Av*(VIN-ISENSE), where Av is the trim gain parameter with a value between 0 and 1, the value of Av being determined by the trim code mentioned above. This causes the current at R1 to I (R1) =(VIN-ISENSE)*Av / R1, where VIN-ISENSE = ISENSE*RS, i.e. I( R1 )=(ISENSE*Rs)*Av / R1.

[0054] For the selection of components as examples in Fig. 4, the first output node 404 generates a first system output monitoring current given by Equation 5: IOUTP=IREF+(IIN*RS*Av / R1) where IREF is the current supplied by the first current source 444, IIN is the system load current 410, RS is the value of the resistor RS, Av is the trim gain, and R1 is the value of the resistor R1.

[0055] For the selection of components as in Fig. 4 selected examples, the second output node 406 generates a second system output monitoring current IOUTM given by Equation 6: IOUTM=IREF−(IIN*RS*Av / R1) where IREF is the current supplied by the first current source 446, IIN is the system load current 410, RS is the value of the resistor RS, Av is the trim gain, and R1 is the value of the resistor R1. Taking the difference between the two outputs, we get Equation 7: IOUTP−IOUTM=2*IIN*Av*(RS / R1)

[0056] It may be helpful to keep the two resistors (e.g., resistive element RS and resistive element R1) at the same temperature to maintain stable gain over temperature and reduce errors due to aging. Since the greatest power dissipation occurs in resistive element RS (through which the full, large system current can flow), resistive element R1 can be designed to be thermally coupled to resistive element RS, so that both resistive elements RS and R1 are at approximately the same temperature and experience the same temperature swings. This may involve forming a "thermal cage" to keep resistive element RS and resistive element R1 at the same temperature.Thus, in some examples, resistive element RS and resistive element R1 are thermally coupled to maintain a temperature of the second resistive element at or near a temperature of the first resistive element when a system load current flows through and heats the first resistor. Further information can be found in commonly assigned U.S. Patent 11,378,595, entitled "Low temperature coefficient current sensor," by Michael D. Petersen et al., the entire contents of which are incorporated herein by reference.

[0057] Fig. 5 shows another example of a bidirectional system current sensor module 500 architecture using various techniques of this disclosure. Many of the components in the bidirectional system current sensor module 500 are similar to the bidirectional system current sensor module 400 of Fig. 4 and will not be described in detail again for the sake of brevity.

[0058] Instead of the specific representation of an R2R digital-to-analog voltage converter, as in Fig. 4, the first trimming circuit 414 and the second trimming circuit 416 in the illustration of the bidirectional system current sensor module 500 consist of a digital-to-analog converter with a low output impedance (as opposed to an R2R digital-to-analog converter, which has an output impedance of R). As in Fig. 5, a resistor R6 (with resistance value R) is coupled between the output 430 of the first trim circuit 414 and the non-inverting input of the amplifier 428, and a resistor R7 (e.g., with a resistance value R) is coupled between the output 432 of the second trim circuit 416 and the inverting input of the amplifier 428.

[0059] Fig.6 is a flowchart of an example method 600 for detecting or measuring a bidirectional system load current. At block 602, the method 600 includes: in response to a system load current flowing in a first direction between an input node and a system current monitoring node via a first resistor, shunting a first output monitoring current across a second resistor.

[0060] At block 604, the method 600 includes adjusting, using a first trim circuit coupled across and in parallel with the first resistor, a trim gain between the input node and the system current monitoring node.

[0061] At block 606, the method 600 includes controlling, using a first amplifier configured in a closed feedback loop, the first output monitoring current such that a voltage difference at a first and a second input of the first amplifier tends to be reduced or minimized.

[0062] At block 608, method 600 includes: in response to the system load current flowing in a direction opposite the first direction between the input node and the system current monitor node via the first resistor, shunting a second output monitor current via a third resistor.

[0063] At block 610, the method 600 includes adjusting, using a second trim circuit coupled across and in parallel with the first resistor, a signal between the input node and the system current monitoring node.

[0064] In some examples, adjusting, using the first trim circuit coupled across and in parallel with the first resistor, the signal between the system load current and the system current monitoring node comprises: receiving a first trim code and a second trim code, and in response modifying a voltage between the input node and the system current monitoring node to produce a voltage proportional to the system load current at the first resistor and the first trim code, wherein a trim represented by the first and second trim codes provides variable attenuation based on the first and second trim codes.In some examples, adjusting, using the first and second trimming circuits coupled across and in parallel with the first resistor, the signal between the input node and the system current monitoring nodes comprises using a digital-to-analog converter to modify a resistance value of a variable resistor coupled across and in parallel with the first resistor.

[0065] At block 612, the method 600 includes controlling, using a second amplifier configured in a closed feedback loop, the second output monitoring current such that a voltage difference at a first and a second input of the second amplifier tends to be reduced or minimized.

[0066] In some examples, method 600 includes: thermally coupling the first resistor and the second and third resistors to maintain a temperature of the second and third resistors at or near a temperature of the first resistor when a system load current flows through the first resistor and heats the first resistor.

[0067] In some examples, method 600 includes modifying or blowing at least one polysilicon fuse. Various comments

[0068] Each of the non-limiting claims or examples described herein may stand alone or may be combined in various permutations or combinations with one or more of the other examples.

[0069] The foregoing detailed description incorporates references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as "examples." Such examples may include elements in addition to those shown or described. However, the inventors of the present invention also contemplate examples in which only the elements shown or described are provided.In addition, the inventors of the present invention also contemplate examples in which any combination or permutation of the elements shown or described (or one or more claims thereof) is used, either with respect to a particular example (or one or more claims thereof) or with respect to other examples (or one or more claims thereof) shown or described herein.

[0070] In the event of any inconsistency between the use of this document and any documents incorporated by reference, the use in this document shall prevail.

[0071] Throughout this document, the terms "a" or "an" are used, as is customary in patent documents, to include one or more elements, regardless of all other instances or uses of "at least one" or "one or more." Throughout this document, the term "or" refers to a non-exclusive or, such that, unless otherwise specified, "A or B includes "A but not B," "B but not A," and "A and B." Throughout this document, the terms "containing" and "in which" are used as the plain English equivalents of the respective terms "having" and "wherein."Furthermore, the terms "including" and "having" in the following claims are open-ended terms, meaning that a system, apparatus, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim is still considered within the scope of that claim. Furthermore, the terms "first," "second," and "third," etc., are used merely as labels and are not intended to impose numerical requirements on their objects.

[0072] Method examples described herein may be at least partially machine- or computer-implemented. Some examples may include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. Implementation of such methods may include code such as microcode, assembly language code, high-level language code, or the like. Such code may include computer-readable instructions for performing various methods. The code may form portions of computer program products. Further, in one example, the code may be tangibly stored on one or more transient, non-transitory, or persistent tangible computer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or flash drives, random access memories (RAMs), read-only memories (ROMs), and the like.

[0073] The above description is intended to be illustrative and not restrictive. For example, the examples described above (or one or more claims thereof) may be used in combination with one another. Other embodiments may be used, such as would be apparent to one of ordinary skill in the art upon review of the above description. The Abstract is provided to comply with 37 CFR §1.72(b) to enable the reader to quickly appreciate the nature of the technical disclosure. It is presented with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This is not to be construed as an intent that any unclaimed disclosed feature is essential to any claim.Rather, the subject matter of the invention may lie in fewer than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, each claim standing on its own as a separate embodiment, and it is intended that such embodiments may be combined with one another in various combinations or permutations. The scope of the invention should be determined by reference to the appended claims, along with the full range of equivalence to which such claims are entitled.

[0074] In one aspect, this disclosure describes various bidirectional current sensing techniques. The described solution uses a tuned thermal substrate, e.g., copper, in conjunction with the front two amplifiers of a three-amplifier instrumentation amplifier. The described bidirectional system current sensor module uses the tuned thermal substrate approach to eliminate the temperature coefficient dependence in the sensor. Behind the front two amplifiers, the circuitry can be varied to support factory gain trimming and voltage or current mode outputs. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 11,378,595 [0028, 0043, 0056]

Claims

[1] Bidirectional system current sensor module comprising: an input node, a first output node, a second output node, and a system power monitoring node; a first output transistor coupled between the input node and the first output node; a second output transistor coupled between the system current monitoring node and the second output node; a first resistor coupled between the input node and the system current monitoring node; a second resistor coupled between the input node and the first output transistor; a third resistor coupled between the system current monitoring node and the second output transistor; a first amplifier including a first amplifier input coupled to the second resistor, a second amplifier input coupled to an output node of a first trim circuit, and an amplifier output coupled to a control node of the first output transistor; and a second amplifier including a first amplifier input coupled to the third resistor, a second amplifier input coupled to an output node of a second trim circuit, and an amplifier output coupled to a control node of the second output transistor, wherein the first output node and the second output node are configured to generate a differential output monitoring current. [2] The bidirectional system current sensor module of claim 1, wherein the first resistor, the second resistor, and the third resistor are thermally coupled to maintain a temperature of the second resistor and the third resistor at or near a temperature of the first resistor when a system current flows through the first resistor and heats the first resistor. [3] A bidirectional system current sensor module according to any one of the preceding claims, wherein the first resistor, the second resistor and the third resistor comprise the same material. [4] A bidirectional system current sensor module according to any one of the preceding claims, wherein, when current flows in a first direction, the first trimming circuit is configured to receive a first trimming code and, in response thereto, couple a corresponding resistance value in parallel with the first resistor to adjust a gain between a system load current and a first output monitoring current, and wherein, when current flows opposite the first direction, the second trimming circuit is configured to receive a second trimming code and, in response thereto, couple a corresponding resistance value in parallel with the first resistor to adjust a gain between the system load current and a second output monitoring current. [5] A bidirectional system current sensor module according to any one of the preceding claims, wherein the first trimming circuit and the second trimming circuit each comprise a corresponding digital-to-analog converter. [6] The bidirectional system current sensor module of claim 5, wherein the digital-to-analog converter comprises a digital-to-analog voltage converter. [7] The bidirectional system current sensor module of claim 6, wherein the digital-to-analog voltage converter comprises an R-2R digital-to-analog converter. [8] The bidirectional system current sensor module of any preceding claim, wherein the first resistor has a first node and a second node, and wherein the first trimming circuit is coupled to the first node and the second node, and wherein the second trimming circuit is coupled to the first node and the second node. [9] A method for detecting or measuring a bidirectional system load current, comprising: in response to a system load current flowing in a first direction between an input node and a system current monitoring node via a first resistor, shunting a first output monitoring current via a second resistor; Adjusting, using a first trimming circuit coupled across and in parallel with the first resistor, a gain between the input node and the system current monitoring node; and controlling, using a first amplifier formed in a closed feedback loop, the first output monitoring current such that a voltage difference at a first and a second input of the first amplifier tends to be reduced or minimized; and in response to the system load current flowing in a direction opposite to the first direction between the input node and the system current monitoring node via the first resistor, shunting a second output monitoring current via a third resistor; Adjusting, using a second trim circuit coupled across and in parallel with the first resistor, a signal between the input node and the system current monitoring node; and controlling, using a second amplifier formed in a closed feedback loop, the second output monitoring current such that a voltage difference at a first and a second input of the second amplifier tends to be reduced or minimized. [10] A method according to claim 9, comprising: thermally coupling the first resistor, the second resistor, and a third resistor to maintain a temperature of the second and third resistors at or near the temperature of the first resistor when a system load current flows through the first resistor and heats the first resistor. [11] The method of claim 9 or 10, wherein adjusting, using the first and second trimming circuits coupled across and in parallel with the first resistor, the signal between the system load current and the system current monitoring node comprises: Receiving a first trim code and a second trim code, and in response modifying a voltage between the input node and the system current monitoring node to produce a voltage proportional to the system load current at the first resistor and the first trim code, wherein a trim represented by the first and second trim codes provides variable attenuation based on the first and second trim codes. [12] The method of any one of claims 9 to 11, wherein adjusting, using the first and second trimming circuits coupled across and in parallel with the first resistor, the signal between the input node and the system current monitoring node comprises: Using a digital-to-analog converter to modify a resistance value of a variable resistor coupled across and in parallel with the first resistor. [13] Bidirectional system current sensor module comprising: an input node, a first output node, a second output node, and a system power monitoring node; a first resistor coupled between the input node and the system current monitoring node, the first resistor having a first node and a second node; a first output transistor coupled between the system current monitoring node and the first output node; a second output transistor coupled between the system current monitoring node and the second output node; a second resistor coupled between the first output transistor and the second output transistor; and a first amplifier comprising: a first amplifier input coupled to an output node of a first trimming circuit and a first amplifier output coupled to a control node of the first output transistor; a second amplifier input coupled to an output node of a second trim circuit, and a second amplifier output coupled to a control node of the second output transistor, wherein the first output node and the second output node are configured to generate a differential output monitoring current. [14] A bidirectional system current sensor module according to claim 13, comprising: the first trimming circuit coupled to receive a voltage of the first input node and a voltage at a node between the first node and the second node; and the second trim circuit coupled to receive the voltage at the node between the first node and the second node and a voltage at the second node. [15] A bidirectional system current sensor module according to claim 13 or 14, comprising: a third resistor and a fourth resistor coupled in series, wherein the first resistor is coupled in parallel with a series combination of the third resistor and the fourth resistor, and wherein the node between the first node and the second node is a node between the third resistor and the fourth resistor. [16] A bidirectional system current sensor module according to any one of claims 13 to 15, comprising: a first current source coupled in series with the first output transistor and configured to induce a first reference current; and a second current source coupled in series with the second output transistor and configured to induce a second reference current. [17] A bidirectional system current sensor module according to any one of claims 13 to 16, wherein the first trimming circuit and the second trimming circuit each comprise a corresponding digital-to-analog converter. [18] The bidirectional system current sensor module of claim 17, wherein the digital-to-analog converter comprises a digital-to-analog voltage converter. [19] The bidirectional system current sensor module of claim 18, wherein the digital-to-analog voltage converter comprises an R-2R digital-to-analog converter. [20] The bidirectional system current sensor module of any one of claims 13 to 19, wherein the first resistor and the second resistor are thermally coupled, and wherein the first resistor and the second resistor comprise the same material.

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