Bidirectional integrated low-temperature coefficient current sensor

Abstract

The invention relates to a bidirectional integrated low temperature coefficient current sensor. Various bi-directional current sensing techniques are described. The described solution utilizes matched thermal substrates, such as copper, for use in conjunction with the first two amplifiers of a three-amplifier instrumentation amplifier. The described bi-directional system current sensor module utilizes a matched thermal substrate approach to eliminate temperature coefficient dependencies in the sensor. Following the lead two amplifiers, the circuit may vary to support factory gain trimming and output of voltage or current mode type.

Description

Technical Field

[0001] This document relates generally to, but is not limited to, current sensors and more specifically to, but is not limited to, laminate-based "zero" temperature coefficient current sensors. Background Art

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

[0003] Discrete sense resistors with low temperature coefficients tend to be made from exotic materials such as iron-chromium or manganese-copper alloys. These exotic materials can achieve low temperature coefficients of resistance (TCR) but can be expensive. Accurately sensing the voltage across such a sense resistor element can also be difficult given the large currents (resulting in an ohmic “IR” voltage drop across the PCB) and small voltage drops across a sense resistor used as a current sensing element, which is necessary to keep power dissipation in the sense resistor reasonable. Some Kelvin sense resistors are available that can include sense points integrated into the sense resistor, for example, but these resistors tend to be more expensive.

[0004] Another approach to sensing large currents is to use a portion of the copper PCB trace itself as the current sensing element. This has the advantage that the PCB trace already exists on the PCB and no additional voltage drop needs to be introduced (e.g. due to a discrete sensing element). However, copper has a large TCR (3900ppm / °C). Therefore, as the PCB temperature changes, either due to changes in ambient temperature or due to power dissipation in the IR drop on the copper trace, the absolute resistance of the sensing element will change. While it is possible to compensate for this effect, such as by using a temperature sensor near the sensing element and some analog or digital signal conditioning in the measurement circuit, this temperature compensation involves additional complexity.

[0005] Additionally, the accuracy of discrete current sensing resistors or the thickness and width of PCB traces may not be well controlled to achieve the desired final system accuracy. Trimming techniques can be applied in the final PCB assembly, but this adds test cost and complexity to the PCB manufacturing process, provided that current can be measured externally or applied accurately enough to achieve the desired trimming target. Summary of the invention

[0006] The present disclosure describes various bidirectional current sensing techniques. The solution described in the present disclosure utilizes a matched thermal substrate, such as copper, in conjunction with the first two amplifiers of a three-amplifier instrumentation amplifier. The described bidirectional system current sensor module utilizes a matched thermal substrate approach to eliminate temperature coefficient dependency in the sensor. Behind the lead two amplifiers, the circuit can be varied to support factory gain trimming and voltage or current mode type outputs.

[0007] In some aspects, the present disclosure is directed 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 comprising a first amplifier input coupled to the second resistor, a second amplifier input coupled to an output node of a first fine-tuning circuit, and an amplifier output coupled to a control node of the first output transistor; and a second amplifier comprising a first amplifier input coupled to the third resistor, a second amplifier input coupled to an output node of a second fine-tuning 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 produce a differential output monitoring current.

[0008] In some aspects, the present disclosure is directed 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 via a second resistor; using a first fine-tuning circuit connected across and in parallel with the first resistor to adjust a gain between the input node and the system current monitoring node; and using a first amplifier configured in a closed-loop feedback loop to control the first output monitoring current in a manner that tends to reduce or minimize a voltage difference between first and second inputs of the first amplifier; 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; using a second fine-tuning circuit connected across and in parallel with the first resistor to adjust a signal between the input node and the system current monitoring node; and using a second amplifier configured in a closed-loop feedback loop to control the second output monitoring current in a manner that tends to reduce or minimize a voltage difference between first and second inputs of the second amplifier.

[0009] In some aspects, the present disclosure is directed 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, wherein the first resistor has 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 an amplifier, comprising: a first amplifier input coupled to the output node of the first fine-tuning circuit, and a first amplifier output coupled to the control node of the first output transistor; a second amplifier input coupled to the output node of the second fine-tuning circuit and a second amplifier output coupled to the control node of the second output transistor, wherein the first output node and the second output node are configured to produce a differential output monitoring current. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the accompanying drawings, which are not necessarily drawn to scale, the same numerals may describe similar components in different views. Similar numerals with different letter suffixes may represent different instances of similar components. The accompanying drawings generally illustrate various embodiments discussed in this document by way of example and not limitation.

[0011] Figure 1 An example of a system current sensor module architecture is shown.

[0012] Figure 2An example of a linear system current sensor module architecture is shown.

[0013] Figure 3 An example of a linear bidirectional system current sensor module architecture using various techniques of the present disclosure is shown.

[0014] Figure 4 Another example of a bidirectional system current sensor module architecture using various techniques of the present disclosure is shown.

[0015] Figure 5 Another example of a bidirectional system current sensor module architecture using various techniques of the present disclosure is shown.

[0016] Figure 6 is a flow chart of an example of a method of sensing or measuring bidirectional system load current. DETAILED DESCRIPTION

[0017] Conventional current sensor control loops use a gain trim term in the denominator. The 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 a high-resolution digital-to-analog converter (DAC) to finely adjust the gain. A high-resolution DAC increases cost and power consumption.

[0018] The inventors have realized 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, which allows the use of a lower resolution DAC to smoothly adjust the gain while maintaining stability and accuracy.

[0019] In addition, the inventors have also 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 sensing resistor. However, a single current sensing resistor for high currents typically has a poor temperature coefficient and poor process variation. The solution described in the present disclosure utilizes a matched thermal substrate, such as copper, in conjunction with the first two amplifiers of a three-amplifier instrumentation amplifier. The described bidirectional system current sensor module utilizes a matched thermal substrate approach to eliminate the temperature coefficient dependency in the sensor. Behind the lead two amplifiers, the circuit can be varied to support factory gain trimming and voltage or current mode type outputs.

[0020] Figure 1 An example of a system current sensor module 100 architecture is shown. The system current sensor module 100 includes an input node 102 for receiving an input voltage VIN, a system current monitoring node 104 that can monitor an output monitoring current ISENSE, and an output node 106 that generates an output monitoring current IOUTP.

[0021] A current "sense" resistor element RS is located between the input node 102 and the system current monitoring node 104, and has a resistance value of about 150 μΩ, for example, and can be used as a primary current sensing element. A large "system load current" 124 from the system flows through the current sense resistor RS.

[0022] Gain setting resistor elements R1 (e.g., 3.19Ω) and R2 (e.g., 0.8Ω) are connected in series between input node 102 and output transistor 108. Figure 1 As shown, trim circuit 110 is coupled in parallel with resistor element R2. Trim circuit 110 is configured to receive a trim code via trim code input 120 and, in response, modify a voltage based on the VIN voltage at node 124, gain setting resistor elements R1 and R2, and the sensor output current flowing through transistor 114.

[0023] The output 122 of the trimming circuit 110 is coupled to the non-inverting (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, such as a gate terminal of a field effect transistor (FET). The amplifier 112 is configured in a closed-loop feedback loop to control the output current IOUTP in a manner that tends to reduce or minimize the voltage difference across the first input 116 and the second input 118 of the amplifier 112.

[0024] The output monitoring current IOUTP of the system current sensor module 100 is given by Equation 1:

[0025] IOUTP = (IIN * RS) / (R1 + AV * R2) Equation 1

[0026] Where IOUTP is the output monitoring current, IIN is the system load current, RS is the resistance of the resistor element RS, R1 is the resistance of the resistor element R1, AV is the gain trim term, and R2 is the resistance of the resistor element R2.

[0027] As shown in Equation 1, the gain trim term AV is in the denominator, which creates a nonlinear gain relationship between IIN and IOUTP. The nonlinear relationship complicates the trim algorithm because small changes in error have a larger effect on the adjusted gain when the error is small, but have a smaller effect when the error is large. This may require a very high-resolution DAC to smoothly adjust the gain.

[0028] The present inventors have recognized that it is desirable to have a gain trim term in the numerator of the equation, which results in a linear relationship, thereby reducing or minimizing the required trim resolution.

[0029] Figure 2An example of a linear system current sensor module 200 architecture is shown. The system current sensor module 200 includes an input node 202 for receiving an input voltage VIN, a system current monitoring node 204 that can monitor an output monitoring current ISENSE, and an output node 206 that generates an output monitoring current IOUTP.

[0030] A current "sense" resistor element RS is located between the input node 202 and the system current monitoring node 204, and has a resistance value of about 150 μΩ, for example, and can be used as a primary current sensing element. A large "system load current" 224 from the system flows through the current sense resistor RS.

[0031] A gain setting resistor element R1 (eg, 3.19Ω) is connected in series between the input node 202 and the output transistor 208. Figure 1 Compared with the system current sensor module 100 in FIG. 1 , the trimming circuit 210 is coupled in parallel with the resistance element RS. The resistance element RS has a first node 226 and a second node 228, and the trimming circuit 310 is coupled to the first node 226 and the second node 228.

[0032] The trim circuit 210 is configured to receive a trim code (“TRIM”) via a trim code input 212 and, in response, modify a voltage between the input node 202 and the system current monitoring node 204. For example, the trim circuit 210 may couple a resistor corresponding to the trim code in parallel with the resistor element RS to adjust a trim gain between the system load current 224 and the output monitoring current.

[0033] In addition, using the technology of the present disclosure, the Figure 1 The resistor network is simplified by adding resistor element R2. By using these techniques, the gain term is now in the numerator of the equation, which results in a linear relationship that reduces or minimizes the required fine-tuning resolution.

[0034] The output monitoring current IOUTP of the system current sensor module 200 is given by Equation 2:

[0035] IOUTP = (IIN * RS * AV) / R1 Equation 2

[0036] Where IOUTP is the output monitoring current, IIN is the system load current, RS is the resistance of the resistor element RS, R1 is the resistance of the resistor element R1, and AV is the gain trim term.

[0037] The output 214 of the trimming circuit 210 is coupled to the non-inverting (first input 216) of the amplifier 220. The source node 211 of the transistor 208 and the resistor R1 is coupled to the 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, such as a gate terminal of a FET. The amplifier 220 is configured in a closed-loop feedback loop to control the output monitoring current IOUTP in a manner that tends to reduce or minimize the voltage difference across the first input 216 and the second input 218 of the amplifier 220.

[0038] Keeping two resistors (e.g., resistor element RS and resistor element R1) at the same temperature may be helpful, for example, to help maintain a stable gain over temperature and to help reduce errors due to aging. Since the greatest power dissipation will occur in resistor element RS (which may have the entire, large system current flowing through it), resistor element R1 may be constructed to be thermally coupled to resistor element RS so that resistor elements RS, R1 are both at approximately the same temperature and experience the same temperature changes. This may include forming a "heat cage" to help keep resistor element RS and resistor element R1 at the same temperature. Thus, in some examples, when the system load current flows through and heats the first resistor, resistor element RS and resistor element R1 are thermally coupled to keep the temperature of the second resistor element at or near the voltage of the first resistor element. Additional information may be found in commonly assigned U.S. Patent 11,378,595, entitled "Low Temperature Coefficient Current Sensor," to Michael D. Petersen et al., the entire contents of which are incorporated herein by reference.

[0039] In some examples, the resistance element RS and the resistance element R1 include the same material. For example, the resistance element RS and the resistance element R1 can both be copper.

[0040] In some examples, trimming circuit 210 may include a digital-to-analog converter.

[0041] The inventors have recognized that Figure 3 As shown, Figure 2 It is desirable that the linear system current sensor module shown be implemented as a bidirectional current sensor.

[0042] Figure 3 An example of a linear bidirectional system current sensor module 300 architecture using various techniques of the present disclosure is shown. The bidirectional system current sensor module 300 includes an input node 302 for receiving an input voltage VIN, a system current monitoring node 304 that can monitor an output monitoring current ISENSE, a first output node 306, and a second output node 308.

[0043] A current "sense" resistive element RS, such as a resistor, is located between input node 302 and system current monitoring node 304, such as having a resistance value of about 150 μΩ, and can be used as a primary current sensing element. A large system load current 310 from the system flows through the current sense resistor RS.

[0044] A first gain setting resistive element R1 (eg, 3.19Ω), such as 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.

[0045] For a system load current flowing in a first direction, e.g., from the input node 302 to the system current monitoring node 304, the first output monitoring current IOUTP is shunted via the resistor R1. The first trimming circuit 318 is configured to receive a first trimming code (“TRIMP”) via the trimming code input 320 and, in response, modify a voltage between the input node 302 and the system current monitoring node 304. For example, the first trimming circuit 318 may couple a resistor corresponding to the first trimming code and connected in parallel with the resistor element RS to adjust a gain between the system load current 310 and the first output monitoring current IOUTP.

[0046] The first output monitor current IOUTP is given by Equation 3:

[0047] IOUTP = (IIN * RS * Avp) / R1 Equation 3

[0048] Where IIN is the system load current 310, Avp is the forward current trim gain and is set with the first trim code TRIMP, RS is the value of the resistor element RS, R1 is the value of the resistor element R1, and IOUTP is 0 in the reverse current.

[0049] The output 322 of the first trimming circuit 318 is coupled to the non-inverting (first amplifier input 324) of the amplifier 326. The inverting input (second input 327) of the amplifier 326 is coupled to the 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 the control node 330 of the first output transistor 312, such as the gate terminal of a FET. The amplifier 326 is configured in a closed-loop feedback loop to control the first output monitoring current IOUTP in a manner that tends to reduce or minimize the voltage difference across the first input 324 and the second input 327 of the amplifier 326.

[0050] So far, the description of the bidirectional system current sensor module 300 is similar to Figure 2To account for system load current flowing in a direction opposite to the first direction, such as from the system current monitoring node 304 to the input node 302, the bidirectional system current sensor module 300 may include additional circuitry.

[0051] A second gain setting resistive element R1A (e.g., 3.19Ω), such as a resistor, is connected in series between the system current monitoring node 304 and the second output node 308. The second output monitor current IOUTM is shunted via the resistor R1A. Like the first trimming circuit 318, the second trimming circuit 332 is coupled to the first node 314 and the second node 316 of the resistor element RS. The second trimming circuit 332 is configured to receive a second trimming code (“TRIMM”) via a trimming code input 334 and, in response, modify a voltage between the input node 302 and the system current monitoring node 304. For example, the second trimming circuit 332 can couple a resistor corresponding to the second trimming code and connected in parallel with the resistor element RS to adjust the gain between the system load current 310 and the second output monitor current IOUTM.

[0052] The second output monitor current, IOUTM, is given by Equation 4:

[0053] IOUTM=(IIN*RS*Avm) / R1A Equation 4

[0054] Where IIN is the system load current 310, Avm is the reverse current trimming gain and is set with the second trimming code TRIMM, RS is the value of the resistor element RS, R1A is the value of the resistor element R1A, and IOUTM is 0 in the forward current.

[0055] The output 336 of the second trimming circuit 332 is coupled to the non-inverting (first amplifier input 338) of the amplifier 340. The inverting input (second amplifier input 342) of the amplifier 340 is coupled to a node between the resistor R1A and the source terminal of a 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-loop feedback loop to control the second output monitoring current IOUTM in a manner that tends to reduce or minimize the voltage difference across the first amplifier input 338 and the second amplifier input 342 of the amplifier 340. Through the bidirectional technique of the present disclosure, the first output node 306 and the second output node 308 are configured to produce a differential output monitoring current.

[0056] In some examples, each of the first fine tuning circuit 318 and the second fine tuning circuit 332 includes a corresponding digital-to-analog converter. In some examples, the digital-to-analog converter includes a voltage digital-to-analog converter, such as an R-2R digital-to-analog converter.

[0057] Keeping the three resistors (e.g., resistor element RS, resistor element R1, and resistor element R1A) at the same temperature may be helpful, for example, to help maintain a stable gain over temperature and to help reduce errors due to aging. Since the greatest power dissipation will occur in resistor element RS (which may have the entire, large system load current 310 flowing through it), resistor elements R1 and R1A may be constructed to be thermally coupled to resistor element RS so that the three resistor elements RS, R1, R1A are at approximately the same temperature and experience the same temperature changes. This may include forming a "heat cage" to help keep resistor elements RS, R1, and R1A at the same temperature. Thus, in some examples, when the system load current 310 flows through the first resistor and heats the first resistor, the first resistor RS, the second resistor R1, and the third resistor R1A are thermally coupled to keep the temperature of the second resistor and the third resistor at or near the temperature of the first resistor. Additional information may be found in commonly assigned U.S. Patent 11,378,595, entitled "Low Temperature Coefficient Current Sensor," to Michael D. Petersen et al., the entire contents of which are incorporated herein by reference.

[0058] In some examples, the resistor elements RS, R1, and R1A include the same material. For example, the resistor elements RS, R1, and R1A can all be copper.

[0059] Figure 4 Another example of a bidirectional system current sensor module 400 architecture using various techniques of the present disclosure is shown. 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.

[0060] A current "sense" resistive element RS, such as a resistor, is located between input node 402 and system current monitoring node 408, such as having a resistance value of about 150 μΩ, and can be used as a primary current sensing element. A large system load current 410 from the system flows through the current sense resistor RS.

[0061] The bidirectional system current sensor module 400 includes a first trimming circuit 414 and a second trimming circuit 416. A trimming code TRIM is applied to the first trimming circuit 414 and the second trimming circuit 416, and in response, the first trimming circuit 414 and the second trimming circuit 416 modify the voltage between the input node 402 and the system current monitoring node 408 to generate a voltage proportional to the system load current across the resistor RS and the trimming code, wherein the trimming represented by the trimming code provides a variable attenuation based on the trimming code.

[0062] The first trimming circuit 414 is coupled to receive the voltage of the first input node 402 and the voltage at a node between the first node 418 and the second node 420 of the resistor 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 the voltage at the second node 220. For example, a resistor R3 (e.g., 1 kΩ) and a resistor R4 (e.g., 1 kΩ) are coupled in series, where the resistor RS is coupled in parallel with the series combination of the resistors R3 and R4. Node 422 is a node between the resistors R3 and R4.

[0063] In the example shown, node 422 can be coupled to a first input, such as a non-inverting input, of amplifier 424. A second input, such as an inverting input, of amplifier 424 can be connected in a unity gain buffer configuration with the output of amplifier 424. Output 426 can be applied to first trimming circuit 414 and second trimming circuit 416.

[0064] The bidirectional system current sensor module 400 includes an amplifier 428 , such as 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 .

[0065] A first output 434 of the amplifier 428 is coupled to the first output transistor 412, such as a control node 438 of the first output transistor 412. A second output 436 of the amplifier 428 is coupled to the second output transistor 440, such as a control node 442 of the second output transistor 440. The amplifier 428 is in a closed-loop feedback configuration, wherein a resistor R2 is coupled to the non-inverting input and a resistor R5 is coupled to the inverting input. Resistors R2 and R5 can both have similar 2R resistances, such as where R is equal to the output resistance of an R2R voltage digital-to-analog converter. Each of the first trimming circuit 414 and the second trimming circuit 416 can include a corresponding digital-to-analog converter, such as an R2R voltage digital-to-analog converter.

[0066] 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 provide a first reference current IREF, and a second current source 446 coupled in series with the second output transistor 440 and configured to provide a second reference current IREF. A gain setting resistor R1 may be coupled between the first output transistor 412 and the second output transistor 440.

[0067] In operation, the system's feedback drives the amplifier input voltages 430 and 432 to be at nearly equal voltages, producing a voltage proportional to the difference VIN-ISENSE that appears across resistor R1. When trimming is used, VIN-ISENSE = Av*(BA), where Av is the gain, B is the voltage at node B, and A is the voltage at node A. If trimming is 1, then VIN-ISENSE = BA. Specifically, the voltage that appears across R1 is Av*(VIN-ISENSE), where Av is the trimming gain parameter, which has a value between 0 and 1, where the value of Av is determined by the trimming code described above. This causes the current across R1 to be I (R1) =(VIN-ISENSE)*Av / R1, where VIN-ISENSE=ISENSE*RS, so I (R1) =(ISENSE*Rs)*Av / R1.

[0068] for Figure 4 With the component selection of the example, the first output node 404 produces a first system output monitoring current given by Equation 5:

[0069] IOUTP=IREF+(IIN*RS*Av / R1)Equation 5

[0070] Where IREF is the current provided 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.

[0071] To choose Figure 4 As an example, with the components selected in , the second output node 406 generates a second system output monitor current IOUTM given by Equation 6:

[0072] IOUTM = IREF - (IIN * RS * Av / R1) Equation 6

[0073] Where IREF is the current provided 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. Substituting the difference between the two outputs into Equation 7:

[0074] IOUTP-IOUTM=2*IIN*Av*(RS / R1)Equation 7

[0075] Keeping two resistors (e.g., resistor element RS and resistor element R1) at the same temperature may be helpful, for example, to help maintain a stable gain over temperature and to help reduce errors due to aging. Since the greatest power dissipation will occur in resistor element RS (which may have the entire, large system current flowing through it), resistor element R1 may be constructed to be thermally coupled to resistor element RS so that resistor elements RS, R1 are both at approximately the same temperature and experience the same temperature changes. This may include forming a "heat cage" to help keep resistor element RS and resistor element R1 at the same temperature. Thus, in some examples, when the system load current flows through and heats the first resistor, resistor element RS and resistor element R1 are thermally coupled to keep the temperature of the second resistor element at or near the voltage of the first resistor element. Additional information may be found in commonly assigned U.S. Patent 11,378,595, entitled "Low Temperature Coefficient Current Sensor," to Michael D. Petersen et al., the entire contents of which are incorporated herein by reference.

[0076] Figure 5 FIG. 5 shows another example of a bidirectional system current sensor module 500 architecture using various techniques of the present disclosure. Many components in the bidirectional system current sensor module 500 are similar to Figure 4 The bidirectional system current sensing module 400 will not be described in detail for the sake of brevity.

[0077] and Figure 4 Unlike the R2R voltage DAC specifically shown in FIG. 5 , the bidirectional system current sensor module 500 depicts the first trimming circuit 414 and the second trimming circuit 416 as including DACs with low output impedance (compared to an R2R DAC with an R output impedance). Figure 5 As shown, resistor R6 (having resistance R) is coupled between the output 430 of the first fine-tuning circuit 414 and the non-inverting input of the amplifier 428, and resistor R7 (e.g., a resistor having resistance R) is coupled between the output 432 of the second fine-tuning circuit 416 and the inverting input of the amplifier 428.

[0078] Figure 6 is a flow chart of an example of a method 600 of sensing or measuring a bidirectional system load current. At block 602, the method 600 includes shunting a first output monitoring current via a second resistor 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.

[0079] At block 604 , the method 600 includes adjusting a trim gain between an input node and a system current monitoring node using a first trim circuit connected across and in parallel with a first resistor.

[0080] At block 606 , method 600 includes controlling, using a first amplifier configured in a closed feedback loop, a first output monitor current in a manner that tends to reduce or minimize a voltage difference between first and second inputs of the first amplifier.

[0081] At block 608 , the method 600 includes shunting a second output monitoring current via a third resistor in response to the system load current flowing between the input node and the system current monitoring node via the first resistor in a direction opposite to the first direction.

[0082] At block 610 , method 600 includes adjusting a signal between the input node and the system current monitoring node using a second trimming circuit connected across and in parallel with the first resistor.

[0083] In some examples, regulating a signal between a system load current and a system current monitoring node using a first trimming circuit coupled across and in parallel with a first resistor includes receiving a first trimming code and a second trimming code, and in response, modifying a voltage between an input node and a system current monitor node to produce a voltage proportional to the system load current across the first resistor and the first trimming code, wherein the trimming represented by the first and second trimming codes provides a variable attenuation based on the first and second trimming codes. In some examples, regulating a signal between an input node and a system current monitoring node using first and second trimming circuits coupled across and in parallel with the first resistor includes using a digital-to-analog converter to modify a resistance of a variable resistor coupled across and in parallel to the first resistor.

[0084] At block 612 , method 600 includes controlling, using a second amplifier configured in a closed feedback loop, a second output monitor current in a manner that tends to reduce or minimize a voltage difference between first and second inputs of the second amplifier.

[0085] In some examples, method 600 includes thermally coupling the first resistor with the second and third resistors to maintain the temperature of the second and third resistors at or near the temperature of the first resistor when the system load current flows through the first resistor and heats the first resistor.

[0086] In some examples, method 600 includes modifying or blowing at least one polysilicon fuse.

[0087] Various annotations

[0088] Each non-limiting claim or example described herein may stand alone or in various permutations or combinations with one or more of the other examples.

[0089] The above detailed description includes references to the accompanying drawings that form a part of the detailed description. The accompanying drawings illustrate specific embodiments in which the present invention can be practiced by way of illustration. These embodiments are also referred to as "examples" in this article. Such examples may include elements other than those shown or described. However, the inventors also consider examples that only provide the shown or described elements. In addition, the inventors also consider examples using any combination or permutation of those elements shown or described (or one or more claims thereof), whether with respect to a specific example (or another one or more claims thereof), or with respect to other examples shown or described herein (or one or more claims thereof).

[0090] In the event of an inconsistency in usage between this document and any document incorporated by reference, the usage in this document shall control.

[0091] Throughout this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more, independent of any other instance or usage of "at least one" or "one or more." Throughout this document, the term "or" is used to refer to the non-exclusive, or "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise noted. Throughout this document, the terms "including" and "wherein" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Furthermore, in the following claims, the terms "including" and "comprising" are open-ended, that is, a system, apparatus, article, composition, formulation, or method that includes additional elements in addition to those listed after such terms in a claim is deemed to fall within the scope of the claim. Furthermore, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels and are not intended to impose numerical requirements on their objects.

[0092] The method examples described herein may be implemented at least in part by a machine or computer. Some examples may include a computer-readable medium or a machine-readable medium encoded with instructions, which may be operable to configure an electronic device to perform the method described in the above examples. The implementation of this method may include code, such as microcode, assembly language code, high-level language code, etc. Such code may include computer-readable instructions for performing various methods. The code may form part of a computer program product. In addition, in one example, the code may be tangibly stored on one or more volatile, non-transient or non-volatile 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, a hard disk, a removable disk, a removable optical disk (e.g., an optical disk and a digital video disk), a cassette, a memory card or a memory stick, a random access memory (RAM), a read-only memory (ROM), etc.

[0093] The above description is intended to be illustrative rather than limiting. For example, the above examples (or one or more claims thereof) may be used in combination with each other. Other embodiments may be used, such as by a person of ordinary skill in the art after reading the above description. The abstract is provided to comply with the provisions of Section 1.72 (b) of Chapter 37 of the United States Code of Federal Regulations so that the reader can quickly determine the nature of the technical disclosure. The premise of submitting this document is that this document shall not be used to interpret or limit the scope or meaning of the claims. In addition, in the above detailed description, various features may be combined together to simplify the present disclosure. This should not be interpreted as meaning that unclaimed public features are essential to any claim. On the contrary, the subject matter of the present invention may lie in the partial features of a specific disclosed embodiment. Therefore, the following claims are incorporated into the detailed description as examples or embodiments, each claim exists independently as a separate embodiment, and it is conceivable that these embodiments can be combined with each other in various combinations or arrangements. The scope of the present invention should be determined with reference to the appended claims and the full scope of equivalents enjoyed by these claims.

Claims

1. 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 the output node of the first trimming circuit, and an amplifier output coupled to the 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 the output node of the second trimming circuit, and an amplifier output coupled to the control node of the second output transistor, 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 the temperature of the second resistor and the third resistor at or near the temperature of the first transistor when the system current flows through the first resistor and heats the first resistor. 3 . The bidirectional system current sensor module of claim 1 , wherein the first resistor, the second resistor, and the third resistor comprise a same material.

4. The bidirectional system current sensor module according to claim 1, wherein: When current flows in a first direction, the first trimming circuit is configured to receive a first trimming code and, in response, couple a corresponding resistor in parallel with the first resistor to adjust a gain between the system load current and a first output monitoring current, and Wherein, when the current flows in a direction opposite to the first direction, the second fine-tuning circuit is configured to receive a second fine-tuning code and, in response, couple a corresponding resistor in parallel with the first resistor to adjust the gain between the system load current and the second output monitoring current. 5 . The bidirectional system current sensor module of claim 1 , wherein each of the first fine-tuning circuit and the second fine-tuning circuit comprises a respective digital-to-analog converter. 6 . The bidirectional system current sensor module of claim 5 , wherein the digital-to-analog converter comprises a voltage digital-to-analog converter. 7 . The bidirectional system current sensor module of claim 6 , wherein the voltage digital-to-analog converter comprises an R-2R digital-to-analog converter.

8. The bidirectional system current sensor module according to claim 1, 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 sensing or measuring a load current in a bidirectional system, comprising: shunting a first output monitoring current via a second resistor 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; adjusting a gain between an input node and the system current monitoring node using a first trimming circuit connected across and in parallel with the first resistor; and using a first amplifier configured in a closed feedback loop, controlling a first output monitor current in a manner tending to reduce or minimize a voltage difference between first and second inputs of the first amplifier; and shunting a second output monitoring current via a third resistor in response to the system load current flowing between the input node and the system current monitoring node via the first resistor in a direction opposite to the first direction; using a second trimming circuit connected across and in parallel with the first resistor to adjust a signal between the input node and the system current monitoring node; and Using a second amplifier configured in a closed feedback loop, a second output monitor current is controlled in a manner that tends to reduce or minimize a voltage difference between first and second inputs of the second amplifier.

10. The method according to claim 9, comprising: The first resistor, the second resistor, and the third resistor are thermally coupled to maintain the temperatures 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, wherein regulating the signal between the system load current and the system current monitoring node using the first and second trimming circuits connected across and in parallel with the first resistor 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 a system load current across the first resistor and the first trim code, wherein the trim represented by the first and second trim codes provides a variable attenuation based on the first and second trim codes.

12. The method according to claim 11, wherein: Using the first and second trimming circuits connected across and in parallel with the first resistor to adjust the signal between the input node and the system current monitoring node includes: A digital-to-analog converter is used to modify the resistance of a variable resistor connected across and in parallel with the first resistor.

13. 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, wherein the first resistor has 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 Amplifiers, including: a first amplifier input coupled to an output node of the 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 the second trimming circuit and a second amplifier output coupled to a control node of the second output transistor, The first output node and the second output node are configured to generate a differential output monitoring current.

14. The bidirectional system current sensor module according to claim 13, comprising: the first trimming circuit being coupled to receive a voltage at the first node and a voltage at a node between the first node and the second node; and The second trimming circuit is coupled to receive a voltage at a node between the first node and the second node and a voltage at the second node.

15. The bidirectional system current sensor module according to claim 13, comprising: A third resistor and a fourth resistor coupled in series, wherein the first resistor is coupled in parallel with the series combination of the third resistor and the fourth resistor, and wherein a node between the first node and the second node is a node between the third resistor and the fourth resistor.

16. The bidirectional system current sensor module according to claim 13, comprising: a first current source coupled in series with the first output transistor and configured to provide a first reference current; and The second current source is coupled in series with the second output transistor and is configured to provide a second reference current.

17. The bidirectional system current sensor module of claim 13, wherein each of the first fine-tuning circuit and the second fine-tuning circuit comprises a respective digital-to-analog converter.

18. The bidirectional system current sensor module of claim 17, wherein the digital-to-analog converter comprises a voltage digital-to-analog converter.

19. The bidirectional system current sensor module of claim 18, wherein the voltage digital-to-analog converter comprises an R-2R digital-to-analog converter.

20. The bidirectional system current sensor module of claim 13, 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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