Current Sensing Integrated Circuit and Corresponding Method

Abstract

An integrated circuit is presented. The integrated circuit includes a first terminal, a second terminal, a control terminal, a current monitor terminal, a power transistor coupled between the first terminal and the second terminal, and a replica transistor coupled between the first terminal and the current monitor terminal. The integrated circuit is configured to control a current between the first terminal and the second terminal based on a control signal applied to the control terminal. The integrated circuit is further configured to provide, at the current monitor terminal, a current monitor signal indicative of a value of the current.

Claims

1. An integrated circuit comprising a first terminal, a second terminal, a control terminal, a current monitor terminal, a power transistor coupled between the first terminal and the second terminal, and a replica transistor coupled between the first terminal and the current monitor terminal, wherein the integrated circuit is configured to: control a current between the first terminal and the second terminal based on a control signal applied to the control terminal; and provide, at the current monitor terminal, a current monitor signal indicative of a value of the current.

2. The integrated circuit of claim 1, wherein the control terminal is coupled to a control node of the power transistor, and wherein the control terminal is coupled to a control node of the replica transistor.

3. The integrated circuit of claim 1, wherein a controlled section of the power transistor is coupled between the first terminal and the second terminal, and wherein a controlled section of the replica transistor is coupled between the first terminal and the second terminal.

4. The integrated circuit of claim 1, wherein an on-resistance of the replica transistor is K-times larger than an on-resistance of the power transistor.

5. The integrated circuit of claim 4, wherein K is an integer between 1000 and 50000.

6. The integrated circuit of claim 1, further comprising a first resistive element coupled in series with the replica transistor between the first terminal and the second terminal, wherein a node connecting the first resistive element with the replica transistor is coupled to the current monitor terminal.

7. The integrated circuit of claim 6, wherein a drain of the power transistor is connected to the first terminal, wherein a drain of the replica transistor is connected to the first terminal, wherein a source of the power transistor is connected to the second terminal, wherein a source of the replica transistor is connected to the current monitor terminal, and wherein the first resistive element is connected between the current monitor terminal and the second terminal.

8. The integrated circuit of claim 6, further comprising a temperature monitor terminal, wherein the integrated circuit is configured to provide, at the temperature monitor terminal, a temperature monitor signal indicative of a temperature of the first resistive element.

9. The integrated circuit of claim 8, further comprising a second resistive element coupled between the temperature monitor terminal and a reference potential.

10. The integrated circuit of claim 1, further comprising an amplifier circuit, wherein a first input of the amplifier circuit is coupled to the power transistor, wherein a second input of the amplifier circuit is coupled to the replica transistor, and wherein a first output of the amplifier circuit is coupled to the current monitor terminal.

11. The integrated circuit of claim 10, wherein the first input of the amplifier circuit is coupled to a source of the power transistor, wherein the second input of the amplifier circuit is coupled to a source of the replica transistor, and wherein a second output of the amplifier circuit is coupled to the source of the replica transistor.

12. The integrated circuit of claim 10, wherein the amplifier circuit is configured to regulate a voltage at a source of the replica transistor such that the voltage at the source of the replica transistor approaches a voltage at a source of the power transistor.

13. A method of operating an integrated circuit, the integrated circuit comprising a first terminal, a second terminal, a control terminal, a current monitor terminal, a power transistor coupled between the first terminal and the second terminal, and a replica transistor coupled between the first terminal and the current monitor terminal, the method comprising: controlling a current between the first terminal and the second terminal based on a control signal applied to the control terminal; and providing, at the current monitor terminal, a current monitor signal indicative of a value of the current.

14. The method of claim 13, further comprising: arranging a first resistive element in series with the replica transistor between the first terminal and the second terminal; and coupling a node connecting the first resistive element with the replica transistor to the current monitor terminal.

15. The method of claim 14, further comprising: coupling a second resistive element between the second terminal and a temperature monitor terminal.

16. The method of claim 15, further comprising: injecting a current into the temperature monitor terminal and, at the same time, measuring a voltage of the temperature monitor terminal; or connecting an external resistor between the temperature monitor terminal and the control terminal; or connecting an external resistor between the temperature monitor terminal and a supply voltage; or forcing a voltage on the temperature monitor terminal and, at the same time, monitoring a current at the temperature monitor terminal.

17. A control circuit comprising a driver circuit, wherein the control circuit is configured to: generate a control signal for turning on or off a power transistor of an integrated circuit; and read a current monitor signal generated by the integrated circuit, wherein the current monitor signal is indicative of a current flowing through the power transistor.

18. The control circuit of claim 17, wherein the control circuit is further configured to read a temperature monitor signal generated by the integrated circuit, and wherein the temperature monitor signal is indicative of a temperature within the integrated circuit.

19. The control circuit of claim 18, wherein the control circuit is further configured to adjust the read current monitor signal based on the read temperature monitor signal.

20. The control circuit of claim 18, wherein the control circuit is configured to read the temperature monitor signal by: injecting a current into the temperature monitor terminal and, at the same time, measuring a voltage of the temperature monitor terminal; or connecting an external resistor between the temperature monitor terminal and the control terminal; or connecting an external resistor between the temperature monitor terminal and a supply voltage; or forcing a voltage on the temperature monitor terminal and, at the same time, monitoring a current at the temperature monitor terminal.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] The present invention is illustrated by way of example, and not by way of limitation, in the figures in which like reference numerals refer to similar or identical elements, and in which:

[0043] FIG. 1 shows an exemplary circuit diagram of an integrated circuit with current sensing capabilities,

[0044] FIG. 2 shows an exemplary circuit diagram of an integrated circuit with current and temperature sensing capabilities,

[0045] FIG. 3 shows an exemplary compensation circuit for temperature-compensated current sensing using an exemplary integrated circuit with both current and temperature sensing capabilities,

[0046] FIG. 4 shows the temperature dependency of the sensed currents,

[0047] FIG. 5 shows two integrated circuits according to FIG. 1 connected in parallel,

[0048] FIG. 6 shows another exemplary circuit diagram of an integrated circuit with current sensing capabilities, and

[0049] FIG. 7 shows two integrated circuits according to FIG. 6 connected in parallel.

DETAILED DESCRIPTION

[0050] FIG. 1 shows an exemplary circuit diagram of an integrated circuit 1 with current sensing capabilities. The integrated circuit 1 comprises a first terminal 6, a second terminal 7, a control terminal 5, a current monitor terminal 8, a power transistor 2 coupled between the first terminal and the second terminal, and a replica transistor 3 coupled between the first terminal and the current monitor terminal. The integrated circuit 1 controls a current between the first terminal 6 and the second terminal 7 based on a control signal applied to the control terminal 5. Due to the dimensioning of both transistors, said current is mainly flowing through the power transistor 2, and only a small current is flowing through the replica transistor 3. The current is controlled in a sense that both transistors are, depending on the control signal, either turned on or off. In FIG. 1, the body diodes 21 and 31 of both transistors are depicted. The integrated circuit 1 generates, at the current monitor terminal 8, a current monitor signal indicative of a value of said current. The integrated circuit 1 comprises a first resistive element 4 coupled in series with the replica transistor 3 between the first terminal 6 and the second terminal 7. A node connecting the first resistive element 4 with the replica transistor 3 is coupled to the current monitor terminal 8. In other words, the integrated circuit 1 comprises the replica transistor 3 and the resistive element 4 as current sensing means.

[0051] The integrated circuit 1 may provide the following advantages: bidirectional sensing without any charge pumps, simpler circuit for external amplifier, bandwidth defined by the replica transistor, limited impact on package and MOSFET on-resistance RDSon, easy to have second source, and the resistor may be embedded on the MOSFET die.

[0052] However, the current monitor signal provided at the current monitor terminal may show a dependency on temperature. By construction, the voltage VMON at the current monitor terminal may be regarded as a partition of the drain-source voltage of the power transistor 2 (Vds=Iload?RDSon) by using the replica transistor's 3 on-resistance RDSon and the resistance of the integrated sense resistor 4. As a result, the current monitor signal VMON is affected by self-heating effects when the current through the power transistor 2 increases.

[0053] An example for an improved integrated circuit which addresses this temperature dependency is illustrated in FIG. 2. FIG. 2 shows an exemplary circuit diagram of an integrated circuit 1 with current and temperature sensing capabilities. This integrated circuit 1 comprises, in addition to the elements already described in the context of FIG. 1, a temperature monitor terminal 10 for providing a temperature monitor signal indicative of a temperature of the first resistive element 4 (or in general: a temperature associated with the power transistor 2). The integrated circuit 1 further comprises a second resistive element 9 coupled between the temperature monitor terminal 10 and a reference potential. In the depicted example, the reference potential is chosen to be the source of the power transistor 2.

[0054] FIG. 3 shows an exemplary compensation circuit 30 for temperature-compensated current sensing using an exemplary integrated circuit 1 with both current and temperature sensing capabilities. Compensation circuit 30 comprises a resistor 31 connected between the gate driver signal generated by the gate driver and the temperature monitor terminal 10 of the integrated circuit 1. The exemplary compensation circuit 30 also comprises a voltage controlled current source (VCCS) 32 (for example an operational transconductance amplifier (OTA) or Gm-stage) for generating a compensation current Icomp 33 based on a voltage difference between the temperature monitor terminal 10 and the second terminal 7 of the integrated circuit 1 (which may be typically connected to a reference potential). The compensation current 33 is then used to compensate the current monitor signal provided at the current monitor terminal 8. In FIG. 3, a compensation amplifier 34 is generating the compensated current monitor signal 35 based on a voltage difference between the current monitor terminal 8 and the second terminal 7 of the integrated circuit 1.

[0055] The compensation circuit 30 can be placed in a dedicated IC (e.g. gate driver) or in the controller (e.g. digital controller for the converter or protection controller). Alternatively, an external amplifier can be used. In many applications, there is a microcontroller with accurate an analog-to-digital converter. In this case, the current and temperature sense outputs can be directly digitized by the microcontroller and all processing can be implemented digitally.

[0056] FIG. 4 shows the temperature monitor signal 40 at the temperature monitor terminal 10 for different output currents, and the compensation current monitor signal 35 for different output currents. FIG. 5 shows two integrated circuits according to FIG. 1 connected in parallel.

[0057] FIG. 6 shows another exemplary circuit diagram of an integrated circuit 60 with current sensing capabilities. The integrated circuit 60 comprises a first terminal 67, a second terminal 69, a control terminal 68, a current monitor terminal 70, a power transistor 62 coupled between the first terminal and the second terminal, and a replica transistor 63 coupled between the first terminal and the current monitor terminal. The integrated circuit 60 controls a current between the first terminal 67 and the second terminal 69 based on a control signal applied to the control terminal 68. Due to the dimensioning of both transistors, said current is mainly flowing through the power transistor 62, and only a small current is flowing through the replica transistor 63. The current is controlled in a sense that both transistors are, depending on the control signal, either turned on or off. In FIG. 6, the body diodes 64 and 65 of both transistors are illustrated. The integrated circuit 60 generates, at the current monitor terminal 70, a current monitor signal indicative of a value of said current. For this purpose, the integrated circuit 70 comprises an amplifier circuit 66, wherein a first input of the amplifier circuit is coupled to the power transistor 62, wherein a second input of the amplifier circuit is coupled to the replica transistor 63, and wherein a first output of the amplifier circuit is coupled to the current monitor terminal 70. The first input of the amplifier circuit 66 is coupled to the source of the power transistor 62, and the second input of the amplifier circuit 66 is coupled to the source of the replica transistor 63, and a second output of the amplifier circuit 66 is coupled to the source of the replica transistor 63 to form a feedback loop. In other words, unlike the integrated circuit 1 in FIG. 1, where the source of the replica transistor is left floating, the integrated circuit 60 in FIG. 6 comprises a feedback loop to force the voltage at the source of the replica transistor to same (or almost the same) voltage as the voltage at the source of the power transistor. In this way, current sensing with high accuracy may be achieved. Furthermore, the current monitor terminal IMON forms an efficient interface to be coupled with a microcontroller MCU.

[0058] Thus, in summary, the integrated circuit 60 comprises the replica transistor 63 and the amplifier circuit 66 as current sensing means. FIG. 7 shows two integrated circuits according to FIG. 6 connected in parallel.

[0059] Terms such as first, second, and the like, are used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.

[0060] As used herein, the terms having, containing, including, comprising and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles a, an and the are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[0061] The expression and/or should be interpreted to cover all possible conjunctive and disjunctive combinations, unless expressly noted otherwise. For example, the expression A and/or B should be interpreted to mean only A, only B, or both A and B. The expression at least one of should be interpreted in the same manner as and/or, unless expressly noted otherwise. For example, the expression at least one of A and B should be interpreted to mean only A, only B, or both A and B.

[0062] It is to be understood that the features of the various embodiments described herein may be combined with each other, unless specifically noted otherwise.

[0063] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.