Electronic Circuit and Method for Resetting a Magnetoresistance Element

• US 20100026288A1
• Filed: 07/31/2008
• Published: 02/04/2010
• Est. Priority Date: 07/31/2008
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Taylor, William P., Sauber, John
• Granted Patent: US 8,063,634 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 15/205 using magneto-resistance devices, e.g. field plates
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00

Abstract

An electronic circuit includes a primary magnetoresistance element for providing a first output signal proportional to a magnetic field. The primary magnetoresistance element has a primary maximum response axis. The primary magnetoresistance element also has a hysteresis characteristic. The electronic circuit also includes a reset conductor disposed proximate to the magnetoresistance element. The electronic circuit also includes a secondary magnetic field sensing element for providing a second output signal proportional to a magnetic field. The secondary magnetic field sensing element has a secondary maximum response axis, which, in some embodiments, is substantially perpendicular to the primary maximum response axis. In operation, the primary magnetoresistance is reset in accordance with an excessive magnetic field sensed by the secondary magnetic field sensing element.

Claims

1. An electronic circuit, comprising:

a primary magnetoresistance element for providing a first output signal proportional to a magnetic field, wherein the primary magnetoresistance element has a primary maximum response axis, wherein the primary magnetoresistance element has a hysteresis characteristic;

a reset conductor disposed proximate to the magnetoresistance element;

a secondary magnetic field sensing element for providing a second output signal proportional to a magnetic field, wherein the secondary magnetic field sensing element has a secondary maximum response axis; and

a comparison circuit coupled to receive the second output signal, configured to compare the second output signal to a threshold signal, and configured to generate a reset current carried by the reset conductor in response to the comparison, wherein, in response to the reset current, the reset conductor is configured to generate a reset magnetic field at the primary magnetoresistance element to temporarily force the magnetoresistance element to a saturation region of the hysteresis characteristic.

2. The electronic circuit of claim 1, wherein the secondary maximum response axis is substantially perpendicular to the primary maximum response axis.

3. The electronic circuit of claim 1, wherein the primary magnetoresistance element comprises a giant magnetoresistance element.

4. The electronic circuit of claim 1, wherein the primary magnetoresistance element comprises two primary magnetoresistance elements.

5. The electronic circuit of claim 4, wherein the two primary magnetoresistance elements have opposite polarities.

6. The electronic circuit of claim 4, wherein the reset magnetic field is generated so as to temporarily force one of the two primary magnetoresistance elements to a highest resistance and the other one of the two primary magnetoresistance elements to a lowest resistance.

7. The electronic circuit of claim 4, wherein the reset magnetic field is generated so as to temporarily force both of the two primary magnetoresistance elements to a highest resistance or to a lowest resistance.

8. The electronic circuit of claim 1, further comprising a current carrying conductor disposed proximate to the primary magnetoresistance element, wherein the first output signal is proportional to a sensed current magnetic field generated by a current carried by the current carrying conductor, wherein the electronic circuit is configured as a current sensor.

9. The electronic circuit of claim 1, wherein the reset conductor comprises a coil.

10. The electronic circuit of claim 1, wherein the comparison circuit comprises:

a comparator coupled to receive the output signal, coupled to receive the threshold signal, and configured to generate a comparison signal; and

a monostable multivibrator coupled to receive the comparison signal and configured to generate the reset current.

11. The electronic circuit of claim 1, wherein the secondary magnetic field sensing element comprises a secondary magnetoresistance element.

12. The electronic circuit of claim 1, wherein the secondary magnetic field sensing element comprises a secondary Hall effect element.

13. The electronic circuit of claims 12, wherein the Hall effect element is disposed on a substrate die with at least one amplifier.

14. The electronic circuit of claim 1, wherein the hysteresis characteristic is a function of resistance versus an applied magnetic field and a graph of the hysteresis characteristic has a parallelogram shape.

15. The electronic circuit of claim 1, wherein the hysteresis characteristic is a function of resistance versus an applied magnetic field and a graph of the hysteresis characteristic has a shape comprising two coupled curves.

16. A method of resetting a primary magnetoresistance element having a primary maximum response axis and a hysteresis characteristic, comprising:

sensing a magnetic field with a secondary magnetic field sensing element having a secondary maximum response axis;

comparing the magnetic field sensed by the secondary magnetic field sensing element to a threshold; and

resetting the primary magnetoresistance element with a reset magnetic field in response to the comparing by temporarily forcing the primary magnetoresistance element to a saturation region of the hysteresis characteristic.

17. The method of claim 16, wherein the secondary maximum response axis is substantially perpendicular to the primary maximum response axis.

18. The method of claim 16 wherein the primary magnetoresistance element comprises a giant magnetoresistance element.

19. The method of claim 16 wherein the primary magnetoresistance element comprises two primary magnetoresistance elements.

20. The method of claim 19 wherein the two primary magnetoresistance elements have opposite polarities.

21. The method of claim 19, wherein the reset magnetic field is generated so as to temporarily force one of the two primary magnetoresistance elements to a highest resistance and the other one of the two primary magnetoresistance elements to a lowest resistance.

23. The method of claim 16, further comprising:

sensing a magnetic field generally parallel to the primary maximum response axis with the primary magnetoresistance element, wherein the magnetic field generally parallel to the primary maximum response axis is generated in response to a sensed current carried by a current-carrying conductor.

22. The method of claim 197 wherein the reset magnetic field is generated so as to temporarily force both of the two primary magnetoresistance elements to a highest resistance or to a lowest resistance.