Magnetic Field Sensor Providing a Movement Detector

• US 20160123771A1
• Filed: 10/31/2014
• Published: 05/05/2016
• Est. Priority Date: 10/31/2014
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: David, Paul A., Taylor, William P.
• Granted Patent: US 9,823,092 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence

Abstract

A magnetic field sensor has a plurality of magnetic field sensing elements and operates as a motion detector for sensing a rotation or other movement of a target object.

Claims

1. A magnetic field sensor for measuring movement of a target object, the movement in an x-z plane within x-y-z Cartesian coordinates with x, y, and z orthogonal axes, a tangent to a direction of movement of a surface of the target object proximate to the magnetic field sensor substantially parallel to the x axis, the magnetic field sensor comprising:

a substrate having a major planar surface within about twenty degrees of parallel to the x-z plane; and

a plurality of magnetic field sensing elements disposed upon the major planar surface of the substrate, each one of the plurality of magnetic field sensing elements having a major response axis substantially parallel to the major planar surface of the substrate, and the plurality of magnetic field sensing elements is configured to generate a respective plurality of magnetic field signals.

2. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements comprises a plurality of magnetoresistance elements.

3. The magnetic field sensor of claim 1, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit comprising;

a non-volatile memory device operable to store a value indicative of a measured operational characteristic of the magnetic field sensor.

4. The magnetic field sensor of claim 3, wherein the stored value is stored during a first time period, and wherein the stored value is recalled and used during a second different time period after the first time period.

5. The magnetic field sensor of claim 1, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit comprising;

an output protocol module operable to use the plurality of magnetic field signals to determine a direction of movement of the target object.

6. The magnetic field sensor of claim 1, further comprising:

a magnet disposed proximate to the substrate, the magnet having at least two poles to generate a magnetic field substantially parallel to the major planar surface of the substrate.

7. The magnetic field sensor of claim 6, wherein the major planar surface of the substrate overlaps the target object such that a line perpendicular to the major planar surface of the substrate intersects the target object.

8. The magnetic field sensor of claim 1, wherein the target object comprises a ring magnet having a plurality of alternating north and south poles, the target object to generate a magnetic field substantially parallel to the major planar surface of the substrate.

9. The magnetic field sensor of claim 8, wherein the major planar surface of the substrate overlaps the target object such that a line perpendicular to the major planar surface of the substrate intersects the target object.

10. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements is arranged in a line within about twenty degrees of parallel to the tangent to the direction of movement of the target object.

11. The magnetic field sensor of claim 10, wherein the plurality of magnetic field sensing elements comprises a quantity of magnetic field sensing elements in a range of two to nine magnetic field sensing elements.

12. The magnetic field sensor of claim 10, wherein the electronic circuit further comprises:

an output protocol module operable to use the plurality of magnetic field signals to determine a direction of movement of the target object.

13. The magnetic field sensor of claim 10, further comprising:

a non-volatile memory device operable to store a value indicative of a measured operational characteristic of the magnetic field sensor.

14. The magnetic field sensor of claim 10, wherein the plurality of magnetic field sensing elements comprises a plurality of magnetoresistance elements.

15. The magnetic field sensor of claim 10, wherein maximum response axes of the plurality of magnetic field sensing elements are substantially parallel to each other.

16. The magnetic field sensor of claim 10, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit comprising;

a plurality of analog or digital comparators configured to compare each respective one of the plurality of magnetic field signals to a threshold signal to generate a plurality of binary signals, wherein states of the plurality of binary signals are indicative of a position of the target object relative to the plurality of magnetic field sensing elements.

17. The magnetic field sensor of claim 16, wherein the electronic circuit further comprises:

an output protocol module operable to use the plurality of binary signals to determine a direction of movement of the target object.

18. The magnetic field sensor of claim 16, wherein the electronic circuit further comprises:

a non-volatile memory device operable to store a value indicative of a measured operational characteristic of the magnetic field sensor.

19. The magnetic field sensor of claim 10, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit operable to determine a position of the target object relative to the plurality of magnetic field sensing elements.

20. The magnetic field sensor of claim 10, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit comprising;

at least one analog-to digital converter operable to convert the plurality of magnetic field signals to generate a plurality of binary signals, wherein states of the plurality of binary signals are indicative of a position of the object relative to the plurality of magnetic field sensing elements.

21. The magnetic field sensor of claim 20, wherein the at least one analog-to-digital converter comprises a plurality of analog-to-digital converters, each one of the plurality of analog-to-digital converters coupled to a respective one of the plurality of magnetic field sensing elements.

22. The magnetic field sensor of claim 10, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit comprising;

a processor configured to compare each respective one of the plurality of magnetic field signals to a respective threshold signal to generate a plurality of binary signals, wherein states of the plurality of binary signals are indicative of a position of the target object relative to the plurality of magnetic field sensing elements.

23. The magnetic field sensor of claim 22, wherein the electronic circuit further comprises:

a. threshold calculation module coupled to receive signals representative of the plurality of magnetic field signals, the threshold calculation module configured to generate a plurality of threshold values indicative of amplitudes of the plurality of magnetic field signals;

a nonvolatile memory device operable to store the plurality of threshold values; and

a plurality of analog or digital comparators, the memory device operable to provide the plurality of threshold values as input values to the plurality of analog or digital comparators.

24. The magnetic field sensor of claim 23, wherein the plurality of threshold values is stored during a time period when the electronic circuit is powered down and wherein the plurality of threshold values is provided to the plurality of analog or digital comparators when the electronic circuit powers up.

25. The magnetic field sensor of claim 23, wherein the plurality of threshold values is stored during a first time period, and wherein the plurality of threshold values is provided as the input values to the plurality of analog or digital comparators during a second different time period after the first time period.

26. The magnetic field sensor of claim 22, wherein the electronic circuit further comprises:

an output protocol module coupled to the processor and operable to use the plurality of binary signals to determine a direction of movement of the target object.

27. The magnetic field sensor of claim 22, further comprising:

a non-volatile memory device coupled to the processor and operable to store a value indicative of a measured operational characteristic of the magnetic field sensor.

28. The magnetic field sensor of claim 6, wherein the plurality of magnetic field sensing elements comprises two magnetic field sensing elements configured to generate two respective magnetic field signals, the magnetic field sensor further comprising:

an electronic circuit disposed upon the substrate, the electronic circuit comprising;

a differential amplifier coupled to receive a signal representative of the two magnetic field signals and configured to generate an output signal indicative of a position of the target object relative to the plurality of magnetic field sensing elements.

29. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements is formed as at least one circular vertical Hall (CVH) sensing element.

30. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements comprises a plurality of vertical Hall Effect elements.

31. The magnetic field sensor of claim 1, wherein the target object comprises a ferromagnetic tooth of a gear configured to rotate.

32. The magnetic field sensor of claim 1, wherein the target object comprises a ferromagnetic ring magnet configured to rotate.

33. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements is arranged in an are proximate to the target object, and wherein maximum response axes of the plurality of magnetic field sensing elements are substantially parallel to each other.

34. The magnetic field sensor of claim 1, wherein the plurality of magnetic field sensing elements is arranged in an arc proximate to the target object, and wherein maximum response axes of the plurality of magnetic field sensing elements are not substantially parallel to each other.

35. The magnetic field sensor of claim 1, wherein the substrate overlaps the target object such that a line perpendicular to the major surface of the substrate intersects the target object.

36. The magnetic field sensor of claim 1, further comprising:

a non-volatile memory device coupled to the plurality of magnetic field sensing elements and operable to store a value indicative of a measured operational characteristic of the magnetic field sensor.

37. The magnetic field sensor of claim 1, wherein the target object comprises a ferromagnetic target object.

38. The magnetic field sensor of claim 1, wherein the target object comprises a ferromagnetic gear.

39. The magnetic field sensor of claim 1, wherein the target object comprises a ferromagnetic ring magnet.

40. The magnetic field sensor of claim 1, wherein the target object comprises a non-ferromagnetic conductive target object.

41. The magnetic field sensor of claim 1, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit comprising;

a plurality of analog or digital comparators configured to compare each respective one of the plurality of magnetic field signals to a threshold signal to generate a plurality of binary signals, wherein states of the plurality of binary signals are indicative of a position of the target object relative to the plurality of magnetic field sensing elements.

42. The magnetic field sensor of claim 1, further comprising:

an electronic circuit disposed upon the substrate and coupled to the plurality of magnetic field sensing elements, the electronic circuit comprising;

at least one analog-to digital converter operable to convert the plurality of magnetic field signals to generate a plurality of binary signals, wherein states of the plurality of binary signals are indicative of a position of the object relative to the plurality of magnetic field sensing elements.