US-12618875-B2 - Current sensor with magnetic and resistive sensing and shared calibration

Abstract

A current sensor for sensing a current through a conductor includes a magnetic field sensing element configured to generate a magnetic field signal indicative of a magnetic field associated with the current through the conductor, a first processing path responsive to the magnetic field signal and configured to generate a first current sensor output signal, a resistive element coupled to the conductor, a second processing path coupled across the resistive element and configured to measure a voltage across the resistive element and generate a second current sensor output signal, and a shared processor configured to calibrate the first processing path and second processing path. The shared processor can be configured to generate one or more of a sensitivity calibration signal, a temperature calibration signal, an offset calibration signal, or a lifetime drift calibration signal.

Inventors

• Emil Pavlov

Assignees

• ALLEGRO MICROSYSTEMS, LLC

Dates

Publication Date

20260505

Application Date

20240524

Claims (19)

1. 1 . A current sensor for sensing a current through a conductor, comprising: a magnetic field sensing element configured to generate a magnetic field signal indicative of a magnetic field associated with the current through the conductor; a first processing path responsive to the magnetic field signal and configured to generate a first current sensor output signal; a resistive element coupled to the conductor; a second processing path coupled across the resistive element and configured to measure a voltage across the resistive element and generate a second current sensor output signal; and a shared processor configured to calibrate the first processing path and second processing path.
2. 2 . The current sensor of claim 1 , wherein the shared processor is configured to generate a sensitivity calibration signal.
3. 3 . The current sensor of claim 2 , wherein the sensitivity calibration signal comprises: a first sensitivity calibration signal based on a difference between the magnetic field signal and an expected magnetic field signal associated with a predetermined current through the conductor for coupling to the first processing path; and a second sensitivity calibration signal based on a difference between the measured voltage across the resistive element and an expected voltage across the resistive element associated with the predetermined current through the conductor for coupling to the second processing path.
4. 4 . The current sensor of claim 1 , wherein the shared processor is configured to generate a temperature calibration signal.
5. 5 . The current sensor of claim 4 , wherein the magnetic field sensing element has a first temperature coefficient, the resistive element has a second temperature coefficient, and wherein the magnetic field sensing element and the resistive element are selected so that the first temperature coefficient and the second temperature coefficient are substantially equal in value and opposite in polarity.
6. 6 . The current sensor of claim 4 , further comprising a temperature sensing element positioned adjacent to the magnetic field sensing element and configured to generate a temperature signal indicative of a measured temperature associated with the magnetic field sensing element, wherein the temperature signal is coupled to the shared processor.
7. 7 . The current sensor of claim 6 , wherein the temperature calibration signal comprises: a first temperature compensation signal based on a difference between the magnetic field signal and an expected magnetic field signal associated with the measured temperature for coupling to the first processing path; and a second temperature compensation signal based on a difference between the measured voltage across the resistive element and an expected voltage across the resistive element associated with the measured temperature for coupling to the second processing path.
8. 8 . The current sensor of claim 1 , wherein the shared processor is configured to generate an offset calibration signal.
9. 9 . The current sensor of claim 8 , wherein the offset calibration signal is based on a measured voltage across the resistive element and is coupled to first processing path.
10. 10 . The current sensor of claim 1 , wherein the shared processor is configured to generate a lifetime drift calibration signal.
11. 11 . The current sensor of claim 10 , wherein the lifetime drift calibration signal is based on a measured voltage across the resistive element and is coupled to first processing path.
12. 12 . The current sensor of claim 1 , wherein the first processing path comprises a first front-end amplifier and the second processing path comprises a second front-end amplifier and wherein the calibration signal is coupled to the first front end amplifier and to the second front end amplifier.
13. 13 . A method of calibrating a current sensor comprising: generating a magnetic field signal with a magnetic field sensing element, wherein the magnetic field signal is indicative of a magnetic field associated with a current through a conductor; generating a first current sensor output signal with a first processing path responsive to the magnetic field signal; coupling a resistive element to the conductor; measuring a voltage across the resistive element; generating a second current sensor output signal with a second processing path responsive to the measured voltage coupled across the resistive element; and calibrating the first processing path and the second processing path with a shared processor.
14. 14 . The method of claim 13 , wherein calibrating the first processing path comprises adjusting a sensitivity of the first processing path based on a difference between the magnetic field signal and an expected magnetic field signal associated with a predetermined current through the conductor for coupling to the first processing path and wherein calibrating the second processing path comprises adjusting a sensitivity of the second processing path based on a difference between the measured voltage across the resistive element and an expected voltage across the resistive element associated with the predetermined current through the conductor for coupling to the second processing path.
15. 15 . The method of claim 13 , further comprising: providing the magnetic field sensing element with a first temperature coefficient; and providing the resistive element with a second temperature coefficient that is substantially equal in value and opposite in polarity with respect to the first temperature coefficient.
16. 16 . The method of claim 13 , further comprising measuring a temperature associated with the magnetic field sensing element and adjusting the first processing path based on the measured temperature based on a difference between the magnetic field signal and an expected magnetic field signal associated with the measured temperature for coupling to the first processing path.
17. 17 . The method of claim 16 , further comprising adjusting the second processing path based on a difference between the measured voltage across the resistive element and an expected voltage across the resistive element associated with the measured temperature.
18. 18 . The method of claim 13 , further comprising adjusting an offset the first processing path based on a measured voltage across the resistive element.
19. 19 . The method of claim 13 , further comprising adjusting a lifetime drift the first processing path based on a measured voltage across the resistive element.

Description

BACKGROUND Current sensing sometimes includes one or more magnetic field sensing elements in proximity to a current-carrying conductor. The magnetic field sensing elements generate an magnetic field signal having a magnitude proportional to the magnetic field induced by the current through the conductor. Another type of current sensing methodology includes measuring a voltage drop across the conductor in order to thereby determine the level of current flow through the conductor based on the measured voltage drop and known resistance of the conductor. Such current sensing can be referred to as resistive, or shunt sensing. Current sensor integrated circuits (ICs) are often used in automotive control systems and other safety critical applications. There are a variety of specifications that set forth requirements related to permissible sensor quality levels, failure rates, and overall functional safety. One approach to meeting such mandates has been to use redundant, identical circuits in a sensor integrated circuit. Another approach to meeting a high level of safety standard compliance involves using more than one different (i.e., heterogenous) sensing elements, circuitry and/or methodologies. Various error sources can adversely impact current sensor accuracy including sensitivity variations of the sensing elements, offset variations, effects temperature variations, and lifetime drift degradation. Sensitivity refers generally to the relationship between changes in the sensing element output in response and changes in the sensed current level. Offset refers to an electrical offset that can be introduced in the sensor output signal that can be attributable to various factors such as offset associated with sensing elements and signal processing circuitry. For example, some magnetic field sensing elements, such as Hall Effect elements, exhibit an undesirable DC offset voltage. Variations in the temperature to which a sensor is exposed and mechanical and other stresses on the sensor can also adversely impact sensor output signal accuracy. SUMMARY The present disclosure is directed to circuits and methods for providing shared processing between heterogeneous current sensing processing paths, such as magnetic field sensing and resistive sensing processing paths. Cost, circuit area, and power consumption efficiencies can be achieved by shared processing. Example shared processing can include one or more of sensitivity calibration, temperature calibration, offset calibration, or lifetime drift calibration. According to the disclosure, a current sensor for sensing a current through a conductor includes a magnetic field sensing element configured to generate a magnetic field signal indicative of a magnetic field associated with the current through the conductor, a first processing path responsive to the magnetic field signal and configured to generate a first current sensor output signal, a resistive element coupled to the conductor, a second processing path coupled across the resistive element and configured to measure a voltage across the resistive element and generate a second current sensor output signal, and a shared processor configured to calibrate the first processing path and second processing path. Features may include one or more of the following individually or in combination with other features. The shared processor can be configured to generate a sensitivity calibration signal. The sensitivity calibration signal includes a first sensitivity calibration signal based on a difference between the magnetic field signal and an expected magnetic field signal associated with a predetermined current through the conductor for coupling to the first processing path and a second sensitivity calibration signal based on a difference between the measured voltage across the resistive element and an expected voltage across the resistive element associated with the predetermined current through the conductor for coupling to the second processing path. The shared processor can be configured to generate a temperature calibration signal. The magnetic field sensing element has a first temperature coefficient, the resistive element has a second temperature coefficient, and the magnetic field sensing element and the resistive element are selected so that the first temperature coefficient and the second temperature coefficient are substantially equal in value and opposite in polarity. The temperature sensing element is positioned adjacent to the magnetic field sensing element and configured to generate a temperature signal indicative of a measured temperature associated with the magnetic field sensing element, wherein the temperature signal is coupled to the shared processor. The temperature calibration signal includes a first temperature compensation signal based on a difference between the magnetic field signal and an expected magnetic field signal associated with the measured temperature for coupling to the first processing path