Circuits and methods for generating a self-test of a magnetic field sensor

• US 8,818,749 B2
• Filed: 01/17/2013
• Issued: 08/26/2014
• Est. Priority Date: 02/17/2009
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Friedrich, Andreas P., Foletto, Andrea, Doogue, Michael C., Taylor, William P., Vig, Ravi, Scheller, P. Karl
• Primary Examiner(s): Desta, Elias
• Application Number:
  US13/743,451
• Publication Number:
  US 20130134965A1
• Time in Patent Office: 586 Days
• Field of Search: 702116-117, 702/183, 702/189, 324/202, 257/427, 73/12.2
• US Class Current: 702/117
• CPC Class Codes: G01R 33/0023 Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration G01R33/0017 takes precedence
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A magnetic field sensor includes built in self-test circuits that allow a self-test of most of, or all of, the circuitry of the magnetic field sensor, including self-test of a magnetic field sensing element used within the magnetic field sensor, while the magnetic field sensor is functioning in normal operation.

Claims

1. A magnetic field sensor, comprising:

a magnetic field sensing element supported by a substrate, wherein the magnetic field sensing element is configured to generate a self-test signal responsive to a pulsing self-test magnetic field during one or more self-test time periods;

a self-test circuit supported by the substrate, the self-test circuit comprising;

a self-test current conductor proximate to the magnetic field sensing element, the self-test current conductor for carrying a self-test current to generate the self-test magnetic field;

a processing circuit coupled to receive a signal representative of the self-test signal; and

a diagnostic request processor configured to control the self-test current to be on or off in response to a diagnostic input signal received by the diagnostic request processor or to be indicative of a self-test during one or more time periods in response to a diagnostic clock signal generated by the diagnostic request processor, wherein the diagnostic request processor comprises at least one of;

a decoder coupled to receive the diagnostic input signal, configured to decode the diagnostic input signal, and configured to generate a decoded diagnostic signal, or

an internal diagnostic clock generator configured to generate the diagnostic clock signal to control the self-test current to comprise a group of current pulses during the one or more time periods, wherein,

the diagnostic request processor is configured to generate the diagnostic control signal to control the self-test current in response to at least one of the decoded diagnostic signal or the diagnostic clock signal.

2. The magnetic field sensor of claim 1, wherein the self-test circuit further comprises:

a current generator circuit having an output node at which self-test current pulses are generated, wherein the self-test current conductor is coupled to receive the self-test current pulses resulting in the self-test magnetic field having magnetic field pulses.

3. The magnetic field sensor of claim 2, wherein the current generator is configured to generate the self-test current pulses in response to the diagnostic control signal.

4. The magnetic field sensor of claim 2, wherein the diagnostic input signal comprises control pulses, each control pulse resulting in one self-test current pulse from the current generator.

5. The magnetic field sensor of claim 2, wherein the diagnostic input signal comprises control pulses, each control pulse resulting in a plurality of self-test current pulses from the current generator.

6. The magnetic field sensor of claim 2, wherein the diagnostic input signal comprises a first state during which the current generator generates self-test current pulses and a second state during which the current generator does not generate self-test current pulses.

7. The magnetic field sensor of claim 2, wherein the diagnostic input signal comprises first control pulses with a first duty cycle during which the current generator generates self-test current pulses, and wherein the diagnostic input signal comprises second control pulses with a second duty cycle during which the current generator does not generate self-test current pulses.

8. The magnetic field sensor of claim 2, wherein the diagnostic input signal comprises a binary digital word.

9. The magnetic field sensor of claim 1, wherein the self-test current conductor comprises a conductor supported by the substrate and proximate to the magnetic field sensing element.

10. The magnetic field sensor of claim 1, wherein the self-test current conductor comprises a conductor supported by the substrate and spanning more than one metal layer supported by the substrate.

11. The magnetic field sensor of claim 1, further comprising an electromagnetic shield proximate to the magnetic field sensor.

12. The magnetic field sensor of claim 11, wherein the electromagnetic shield comprises at least one feature configured to reduce an eddy current in the electromagnetic shield when the shield is exposed to an AC magnetic field.

13. The magnetic field sensor of claim 1, wherein the magnetic field sensing element comprises a Hall effect element, wherein the magnetic field sensor further comprises a current or voltage generator coupled to the Hall effect element.

14. The magnetic field sensor of claim 1, wherein the magnetic field sensing element comprises a magnetoresistance element, wherein the magnetic field sensor further comprises a current generator coupled to the magnetoresistance element.

15. The magnetic field sensor of claim 1, wherein the one or more self-test time periods comprises a time period beginning with a power-on of the magnetic field sensor and terminating a predetermined time thereafter.

16. A method of generating a self-test of a magnetic field sensor, comprising:

generating, with a magnetic field sensing element supported by a substrate, a self-test signal responsive to a pulsing self-test magnetic field during one or more self-test time periods;

providing a self-test circuit supported by the substrate, the providing the self-test circuit comprising;

providing a self-test current conductor proximate to the magnetic field sensing element, the self-test current conductor for carrying a self-test current to generate the self-test magnetic field;

providing a processing circuit coupled to receive a signal representative of the self-test signal; and

providing a diagnostic request processor configured to control the self-test current to be on or off in response to a diagnostic input signal received by the diagnostic request processor or to be indicative of a self-test during one or more time periods in response to a diagnostic clock signal generated by the diagnostic request processor, wherein the diagnositc request processor comprises at least one of;

a decoder coupled to receive the diagnostic input signal, configured to decode the diagnostic input signal, and configured to generate a decoded diagnostic signal, or

an internal diagnostic clock generator configured to generate the diagnostic clock signal to control the self-test current to comrprise a group of current pulses during the one or more time periods, wherein,

the diagnostic reguest processor is configured to generate the diagnostic control signal to control the self-test current in response to at least one of the decoded diagnostic signal or the diagnostic clock signal.

17. The method of claim 16, further comprising:

controlling, in response to an internal control signal, the self-test current to comprise a group of current pulses during the one or more time periods.

18. The method of claim 16, wherein the self-test current conductor comprises a conductor supported by the substrate and proximate to the magnetic field sensing element.

19. The method of claim 16, wherein the self-test current conductor comprises a coil supported by the substrate and spanning more than one metal layer supported by the substrate.

20. The method of claim 19, further comprising electromagnetically shielding the magnetic field sensor.

21. The method of claim 16, further comprising electromagnetically shielding the magnetic field sensor.

22. The method of claim 16, wherein the one or more self-test time periods comprises a time period beginning with a power-on of the magnetic field sensor and terminating a predetermined time thereafter.