Circuits and methods for self-calibrating or self-testing a magnetic field sensor

• US 8,680,846 B2
• Filed: 04/27/2011
• Issued: 03/25/2014
• Est. Priority Date: 04/27/2011
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Cesaretti, Juan Manuel, Monreal, Gerardo
• Primary Examiner(s): Vazquez, Arleen M
• Assistant Examiner(s): ALLGOOD, ALESA M
• Application Number:
  US13/095,371
• Publication Number:
  US 20120274314A1
• Time in Patent Office: 1,063 Days
• Field of Search: 324/202, 324/251, 324/260, 702/117, 702/183
• US Class Current: 324/202
• CPC Class Codes: G01R 33/0017 Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration

Abstract

A magnetic field sensor includes a reference-field-sensing circuit channel that allows a calibration or a self-test of the circuitry of the magnetic field sensor. The magnetic field sensor can generate a reference magnetic field to which the magnetic field sensor is responsive.

Claims

1. A magnetic field sensor, comprising:

at least two magnetic field sensing elements;

a first switching circuit coupled to the at least two magnetic field sensing elements, wherein the first switching circuit is configured to couple the at least two magnetic field sensing elements into a measured-field-sensing configuration and into a reference-field-sensing configuration, wherein the first switching circuit is configured to couple the at least two magnetic field sensing elements in parallel so as to respond in cooperation in the presence of an external magnetic field when coupled in the measured-field-sensing configuration, and to couple the at least two magnetic field sensing elements such that the responses to the external magnetic field oppose one another when coupled in the reference-field-sensing configuration, and wherein the first switching circuit is operable to switch back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the first switching circuit is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to the external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration;

a processing circuit coupled to receive the magnetic field signal; and

a feedback circuit coupled to receive a signal representative of the magnetic field signal from the processing circuit and configured to generate a feedback signal to control at least one of a bias signal applied to drive the at least two magnetic field sensing elements or a gain of the processing circuit.

2. The magnetic field sensor of claim 1, wherein the reference magnetic field comprises first and second reference magnetic fields pointing in opposite directions at locations of selected ones of the at least two magnetic field sensing elements, the magnetic field sensor further comprising:

a magnetic field generator operable to generate the first and second reference magnetic fields.

3. The magnetic field sensor of claim 2, wherein the magnetic field generator comprises:

at least two reference field conductor portions proximate to the at least two magnetic field sensing elements, respectively, wherein the at least two reference field conductor portions are configured to carry a reference current to generate the reference magnetic field.

4. The magnetic field sensor of claim 3, further comprising:

a second switching circuit coupled to provide the reference current, wherein the second switching circuit is operable to alternately switch the reference current between a first reference current direction and a second opposite reference current direction synchronously with the first switching rate.

5. The magnetic field sensor of claim 3, wherein the processing circuit is coupled to receive the magnetic field signal from the first switching circuit, wherein the magnetic field signal, during first time periods, is representative of the measured-magnetic-field-responsive signal portion and, during second different time periods interleaved with the first time periods at a rate synchronous with the first switching rate, is representative of the reference-magnetic-field-responsive signal portion, wherein the processing circuit comprise:

a first processing channel time multiplexed to select and to process the signal representative of the measured-magnetic-field-responsive signal portion during the first time periods to generate a first sensor output signal representative of the measured-magnetic-field-responsive signal portion; and

a second different processing channel time multiplexed to select and to process the signal representative of the reference-magnetic-field-responsive signal portion during the second different time periods to generate a second different sensor output signal representative of the reference-magnetic-field-responsive signal portion.

6. The magnetic field sensor of claim 5, wherein the feedback circuit is coupled to receive a signal representative of the second sensor output signal.

7. The magnetic field sensor of claim 5, wherein the measured-field-sensing configuration comprises at least two different alternating measured-field-sensing configurations representative of a chopping of the at least two magnetic field sensing elements.

8. The magnetic field sensor of claim 5, wherein the at least two magnetic field sensing elements are supported by a substrate, and wherein the at least two reference field conductor portions comprise a conductor separate from but proximate to the substrate.

9. The magnetic field sensor of claim 5, wherein the external magnetic field is generated by a measured current carried by a measured-current conductor.

10. The magnetic field sensor of claim 5, wherein the at least two magnetic field sensing elements comprise at least two Hall effect elements.

11. The magnetic field sensor of claim 5, wherein the at least two magnetic field sensing elements comprise at least two magnetoresistance elements.

12. The magnetic field sensor of claim 5, wherein the at least two magnetic field sensing elements are supported by a substrate, and wherein the at least two reference field conductor portions comprise a conductor supported by the substrate and proximate to the magnetic field sensing element.

13. The magnetic field sensor of claim 12, wherein the at least two reference field conductor portions span more than one metal layer supported by the substrate.

14. A method of generating a calibration or a self-test of a magnetic field sensor, comprising:

coupling at least two magnetic field sensing elements into a measured-field-sensing configuration, wherein the coupling the at least two magnetic field sensing elements into the measured-field-sensing comprises coupling the at least two magnetic field sensing elements in parallel so as to respond in cooperation in the presence of an external field,

coupling the at least two magnetic field sensing elements into a reference-field-sensing configuration, wherein the coupling that at least two magnetic field sensing elements into the reference-field-sensing configuration comprises coupling the at least two magnetic field sensing elements such that their responses to the external magnetic field oppose one another,

switching back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the switching is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to the external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration; and

using a signal representative of the magnetic field signal as feedback signal to control at least one of a bias signal applied to drive that at least two magnetic field sensing elements or a gain of a processing circuit coupled to the at least two magnetic field sensing elements.

15. The method of claim 14, wherein the reference magnetic field comprises first and second reference magnetic fields pointing in opposite directions at locations of selected ones of the at least two magnetic field sensing elements.

16. The method of claim 14, further comprising:

generating a reference current to generate the reference magnetic field, wherein the reference magnetic field comprises at least two reference magnetic field portions having respective magnetic field directions directed in opposite directions.

17. The method of claim 16, further comprising;

switching alternately between a first reference current direction and a second opposite reference current direction synchronously with the first switching rate.

18. The method of claim 16, further comprising:

receiving the magnetic field signal from the first switching circuit, wherein the magnetic field signal, during first time periods, is representative of the measured-magnetic-field-responsive signal portion and, during second different time periods interleaved with the first time periods at a rate synchronous with the first switching rate, is representative of the reference-magnetic-field-responsive signal portion;

time multiplexing to select and to process the signal representative of the measured-magnetic-field-responsive signal portion during the first time periods to generate a first sensor output signal representative of the measured-magnetic-field-responsive signal portion; and

time multiplexing to select and to process the signal representative of the reference-magnetic-field-responsive signal portion during the second different time periods to generate a second different sensor output signal representative of the reference-magnetic-field-responsive signal portion.

19. The method of claim 18, further comprising:

using a signal representative of the second sensor output signal as the feedback signal.

20. The method of claim 18, wherein the measured-field-sensing configuration comprises at least two different alternating measured-field-sensing configurations representative of a chopping of the at least two magnetic field sensing elements.

21. The method of claim 18, wherein the at least two magnetic field sensing elements are supported by a substrate, wherein the at least two reference magnetic field portions are generated by at least two reference field conductor portions comprising a conductor separate from but proximate to the substrate.

22. The method of claim 18, wherein the external magnetic field is generated by a measured current carried by a measured-current conductor.

23. The method of claim 18, wherein the at least two magnetic field sensing elements comprise at least two Hall effect elements.

24. The method of claim 18, wherein the at least two magnetic field sensing elements comprise at least two magnetoresistance elements.

25. The method of claim 18, wherein the at least two magnetic field sensing elements are supported by a substrate, and wherein the at least two reference magnetic field portions are generated by at least two reference field conductor portions comprising a conductor supported by the substrate and proximate to the at least two magnetic field sensing elements.

26. The method of claim 25, wherein the at least two reference field conductor portions span more than one metal layer supported by the substrate.

27. A magnetic field sensor, comprising:

at least two magnetic field sensing elements; and

a first switching circuit coupled to the at least two magnetic field sensing elements, wherein the first switching circuit is configured to couple the at least two magnetic field sensing elements into a measured-field-sensing configuration and into a reference-field-sensing configuration, wherein the first switching circuit is operable to switch back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the first switching circuit is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to an external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration, wherein the reference magnetic field comprises first and second reference magnetic fields pointing in opposite directions at locations of selected ones of the at least two magnetic field sensing elements, wherein the magnetic field sensor further comprises;

a magnetic field generator operable to generate the first and second reference magnetic fields, wherein the magnetic field generator comprises;

at least two reference field conductor portions proximate to the at least two magnetic field sensing elements, respectively, wherein the at least two reference field conductor portions are configured to carry a reference current to generate the reference magnetic field, wherein the reference magnetic field comprises at least two reference magnetic field portions having respective magnetic field directions directed in opposite directions, wherein the magnetic field sensor further comprises;

a second switching circuit coupled to provide the reference current, wherein the second switching circuit is operable to alternately switch the reference current between a first reference current direction and a second opposite reference current direction synchronously with the first switching rate.

28. The magnetic field sensor of claim 27, wherein the first switching circuit is configured to couple the at least two magnetic field sensing elements to have respective opposite directions of responses to a magnetic field when coupled in the reference-field-sensing configuration.

29. The magnetic field sensor of claim 27, further comprising a feedback circuit configured to generate a feedback signal to control at least one of a bias signal applied to drive the at least two magnetic field sensing elements or a gain of the first and second processing channels.

30. The magnetic field sensor of claim 27, wherein the measured-field-sensing configuration comprises at least two different alternating measured-field-sensing configurations representative of a chopping of the at least two magnetic field sensing elements.

31. The magnetic field sensor of claim 27, wherein the at least two magnetic field sensing elements are supported by a substrate, and wherein the at least two reference field conductor portions comprise a conductor supported by the substrate and proximate to the magnetic field sensing element.

32. The magnetic field sensor of claim 27, wherein the external magnetic field is generated by a measured current carried by a measured-current conductor.

33. The magnetic field sensor of claim 27, wherein the at least two magnetic field sensing elements comprise at least two Hall effect elements.

34. The magnetic field sensor of claim 27, wherein the at least two magnetic field sensing elements comprise at least two magnetoresistance elements.

35. A magnetic field sensor, comprising:

at least two magnetic field sensing elements; and

a first switching circuit coupled to the at least two magnetic field sensing elements, wherein the first switching circuit is configured to couple the at least two magnetic field sensing elements into a measured-field-sensing configuration and into a reference-field-sensing configuration, wherein the first switching circuit is operable to switch back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the first switching circuit is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to an external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration, wherein the reference magnetic field comprises first and second reference magnetic fields pointing in opposite directions at locations of selected ones of the at least two magnetic field sensing elements, wherein the magnetic field sensor further comprises;

a magnetic field generator operable to generate the first and second reference magnetic fields, wherein the magnetic field generator comprises;

at least two reference field conductor portions proximate to the at least two magnetic field sensing elements, respectively, wherein the at least two reference field conductor portions are configured to carry a reference current to generate the reference magnetic field, wherein the reference magnetic field comprises at least two reference magnetic field portions having respective magnetic field directions directed in opposite directions, wherein the magnetic field sensor further comprises;

a processing circuit coupled to receive the magnetic field signal from the first switching circuit, wherein the magnetic field signal, during first time periods, is representative of the measured-magnetic-field-responsive signal portion and, during second different time periods interleaved with the first time periods at a rate synchronous with the first switching rate, is representative of the reference-magnetic-field-responsive signal portion, wherein the processing circuit comprises;

a first processing channel time multiplexed to select and to process the signal representative of the measured-magnetic-field-responsive signal portion during the first time periods to generate a first sensor output signal representative of the measured-magnetic-field-responsive signal portion; and

a second different processing channel time multiplexed to select and to process the signal representative of the reference-magnetic-field-responsive signal portion during the second different time periods to generate a second different sensor output signal representative of the reference-magnetic-field-responsive signal portion.

36. The magnetic field sensor of claim 35, wherein the first switching circuit is configured to couple the at least two magnetic field sensing elements to have respective opposite directions of responses to a magnetic field when coupled in the reference-field-sensing configuration.

37. The magnetic field sensor of claim 35, further comprising a feedback circuit configured to generate a feedback signal to control at least one of a bias signal applied to drive the at least two magnetic field sensing elements or a gain of the first and second processing channels.

38. The magnetic field sensor of claim 35, wherein the measured-field-sensing configuration comprises at least two different alternating measured-field-sensing configurations representative of a chopping of the at least two magnetic field sensing elements.

39. The magnetic field sensor of claim 35, wherein the at least two magnetic field sensing elements are supported by a substrate, and wherein the at least two reference field conductor portions comprise a conductor supported by the substrate and proximate to the magnetic field sensing element.

40. The magnetic field sensor of claim 35, wherein the external magnetic field is generated by a measured current carried by a measured-current conductor.

41. The magnetic field sensor of claim 35, wherein the at least two magnetic field sensing elements comprise at least two Hall effect elements.

42. The magnetic field sensor of claim 35, wherein the at least two magnetic field sensing elements comprise at least two magnetoresistance elements.

43. A method of generating a calibration or a self-test of a magnetic field sensor, comprising:

coupling at least two magnetic field sensing elements into a measured-field-sensing configuration,

coupling the at least two magnetic field sensing elements into a reference-field-sensing configuration, and

switching back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the switching is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to an external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration, wherein the method further comprises;

generating a reference current to generate the reference magnetic field, wherein the reference magnetic field comprises at least two reference magnetic field portions having respective magnetic field directions directed in opposite directions; and

switching alternately between a first reference current direction and a second opposite reference current direction synchronously with the first switching rate.

44. The method of claim 43, wherein the coupling the at least two magnetic field sensing elements into the reference-field-sensing configuration comprises coupling the at least two magnetic field sensing elements to have respective opposite directions of responses to a magnetic field When coupled in the reference-field-sensing configuration.

45. The method of claim 43, further comprising:

generating a feedback signal to control at least one of a bias signal applied to drive the at least two magnetic field sensing elements or a gain of the first and second processing channels.

46. The method of claim 43, wherein the measured-field-sensing configuration comprises at least two different alternating measured-field-sensing configurations representative of a chopping of the at least two magnetic field sensing elements.

47. The method of claim 43, wherein the at least two magnetic field sensing elements are supported by a substrate, and wherein the at least two reference magnetic field portions are generated by at least two reference field conductor portions comprising a conductor supported by the substrate and proximate to the at least two magnetic field sensing elements.

48. The method of claim 43, wherein the external magnetic field is generated by a measured current carried by a measured-current conductor.

49. The method of claim 43, wherein the at least two magnetic field sensing elements comprise at least two Hall effect elements.

50. The method of claim 43, wherein the at least two magnetic field sensing elements comprise at least two magnetoresistance elements.

51. A method of generating a calibration or a self-test of a magnetic field sensor, comprising:

coupling at least two magnetic field sensing elements into a measured-field-sensing configuration,

coupling the at least two magnetic field sensing elements into a reference-field-sensing configuration, and

switching back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the switching is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to an external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration, wherein the method further comprises;

generating a reference current to generate the reference magnetic field, wherein the reference magnetic field comprises at least two reference magnetic field portions having respective magnetic field directions directed in opposite directions;

receiving the magnetic field signal from the first switching circuit, wherein the magnetic field signal, during first time periods, is representative of the measured-magnetic-field-responsive signal portion and, during second different time periods interleaved with the first time periods at a rate synchronous with the first switching rate, is representative of the reference-magnetic-field-responsive signal portion;

time multiplexing to select and to process the signal representative of the measured-magnetic-field-responsive signal portion during the first time periods to generate a first sensor output signal representative of the measured-magnetic-field-responsive signal portion; and

time multiplexing to select and to process the signal representative of the reference-magnetic-field-responsive signal portion during the second different time periods to generate a second different sensor output signal representative of the reference-magnetic-field-responsive signal portion.

52. The method of claim 51, wherein the coupling the at least two magnetic field sensing elements into the reference-field-sensing configuration comprises coupling the at least two magnetic field sensing elements to have respective opposite directions of responses to a magnetic field when coupled in the reference-field-sensing configuration.

53. The method of claim 51, further comprising:

generating a feedback signal to control at least one of a bias signal applied to drive the at least two magnetic field sensing elements or a gain of the first and second processing channels.

54. The method of claim 51, wherein the measured-field-sensing configuration comprises at least two different alternating measured-field-sensing configurations representative of a chopping of the at least two magnetic field sensing elements.

55. The method of claim 51, wherein the at least two magnetic field sensing elements are supported by a substrate, and wherein the at least two reference magnetic field portions are generated by at least two reference field conductor portions comprising a conductor supported by the substrate and proximate to the at least two magnetic field sensing elements.

56. The method of claim 51, wherein the external magnetic field is generated by a measured current carried by a measured-current conductor.

57. The method of claim 51, wherein the at least two magnetic field sensing elements comprise at least two Hall effect elements.

58. The method of claim 51, wherein the at least two magnetic field sensing elements comprise at least two magnetoresistance elements.

59. A magnetic field sensor, comprising:

at least two magnetic field sensing elements;

a first switching circuit coupled to the at least two magnetic field sensing elements, wherein the first switching circuit is configured to couple the at least two magnetic field sensing elements into a measured-field-sensing configuration and into a reference-field-sensing configuration, wherein the first switching circuit is operable to switch back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the first switching circuit is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to an external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration, wherein the reference magnetic field comprises first and second reference magnetic fields pointing in opposite directions at locations of selected ones of the at least two magnetic field sensing elements;

a processing circuit coupled to receive the magnetic field signal;

a feedback circuit coupled to receive a signal representative of the magnetic field signal from the processing circuit and configured to generate a feedback signal to control at least one of a bias signal applied to drive the at least two magnetic field sensing elements or a gain of the processing circuit; and

a magnetic field generator operable to generate the first and second reference magnetic fields.

60. The magnetic field sensor of claim 59, wherein the magnetic field generator comprises:

at least two reference field conductor portions proximate to the at least two magnetic field sensing elements, respectively, wherein the at least two reference field conductor portions are configured to carry a reference current to generate the reference magnetic field.

61. A method of generating a calibration or a self-test of a magnetic field sensor, comprising:

coupling at least two magnetic field sensing elements into a measured-field-sensing configuration,

coupling the at least two magnetic field sensing elements into a reference-field-sensing configuration,

switching back and forth alternately between the measured-field-sensing configuration and the reference-field-sensing configuration at a first switching rate to provide a magnetic field signal, wherein the switching is configured to generate the magnetic field signal comprising;

a measured-magnetic-field-responsive signal portion responsive to an external magnetic field when coupled in the measured-field-sensing configuration; and

a reference-magnetic-field-responsive signal portion responsive to a reference magnetic field when coupled in the reference-field-sensing configuration, wherein the reference magnetic field comprises first and second reference magnetic fields pointing in opposite directions at locations of selected ones of the at least two magnetic field sensing elements; and

using a signal representative of the magnetic field signal as feedback signal to control at least one of a bias signal applied to drive the at least two magnetic field sensing elements or a gain of a processing circuit coupled to the at least two magnetic field sensing elements.

62. The method of claim 61, further comprising:

generating a reference current to generate the reference magnetic field.