METHODS AND APPARATUS FOR MAGNETIC SENSOR HAVING INTEGRATED COIL

• US 20180011150A1
• Filed: 09/20/2017
• Published: 01/11/2018
• Est. Priority Date: 05/10/2012
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Pepka, Gary T., Taylor, William P.
• Granted Patent: US 11,680,996 B2
• Time in Patent Office: Days
• 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
• CPC Class Codes: G01R 33/09 Magnetoresistive devices

Abstract

Methods and apparatus for a magnetic sensor having a die and sensor circuitry formed in a device layer of the die with a coil integrated with the die to generate a magnetic field. A magnetoresistive magnetic field sensing element on the die detects changes in the magnetic field generated by the coil as a result of the presence of a ferromagnetic target. The sensor circuitry may process the changes in the magnetic field generated by the coil.

Claims

1. A magnetic sensor IC package, comprising:

a die;

sensor circuitry formed in a device layer of the die;

a coil integrated with the die to generate a magnetic field; and

a magnetoresistive magnetic field sensing element on the die to detect changes in the magnetic field generated by the coil as a result of the presence of a ferromagnetic target, wherein the sensor circuitry is configured to process the changes in the magnetic field generated by the coil.

2. The sensor according to claim 1, wherein the magnetoresistive magnetic field sensing element comprises a GMR element.

3. The sensor according to claim 1, further including a constant current source coupled to the coil such that alignment changes of the magnetic field generated by the coil with respect to the magnetic sensing element caused by movement of the target are detected by the magnetic field sensing element.

4. The sensor according to claim 1, wherein the movement of the ferromagnetic target to a first position causes a vector of the magnetic field generated by the coil to align substantially perpendicularly to the magnetic field sensing element which increases the magnetic field observed by the magnetic field sensing element, and further movement of the ferromagnetic target to a second position changes the magnetic field observed by the magnetic field sensing element.

5. The sensor according to claim 1, wherein coil spaces are at least 10 μ

m.

6. The sensor according to claim 1, wherein traces for the coil range from an inner diameter of about 50 μ

m to about 200 μ

m.

7. The sensor according to claim 6, wherein the traces for the coil range from an outer diameter of about 60 μ

m to about 500 μ

m.

8. The sensor according to claim 1, wherein the IC package is configured for an airgap with the target ranging from about 0.5 mm to about 3 mm.

9. The sensor according to claim 1, wherein current through the coil ranges from about 5 μ

A to about 50 μ

A.

10. The sensor according to claim 1, wherein the sensor is configured to use less power for closer airgaps and more power for larger airgarps.

11. The sensor according to claim 1, wherein the coil is substantially flat.

12. The sensor according to claim 1, wherein the only a portion of the magnetic field sensing element overlaps with the coil.

13. The sensor according to claim 1, wherein the magnetic field sensing element is positioned at least in part between the coil and the die.

14. The sensor according to claim 1, wherein the coil is positioned at least in part between the magnetic field sensing element and the die.

15. The sensor according to claim 1, wherein about half of an area of the magnetic field sensing element overlaps with the coil.

16. The sensor according to claim 1, wherein about half of a length of the magnetic field sensing element overlaps with the coil.

17. The sensor according to claim 1, wherein sensor includes a further magnetic field sensing element.

18. The sensor according to claim 1, further including a pulse current source coupled to the coil.

19. The sensor according to claim 1, wherein the magnetic field sensing element has at least a portion that overlaps the coil.

20. A magnetic field sensor, comprising:

a die;

sensor circuitry formed in a device layer of the die;

a coil means integrated with the die to generate a magnetic field; and

a magnetic field sensing means on the die to detect changes in the magnetic field generated by the coil means as a result of the presence of a ferromagnetic target, wherein the sensor circuitry is configured to process the changes in the magnetic field generated by the coil means.

21. The sensor according to claim 20, wherein the magnetic field sensing means comprises a GMR element.

22. The sensor according to claim 20, further including a constant current source means coupled to the coil means such that alignment changes of the magnetic field generated by the coil means with respect to the magnetic field sensing means caused by movement of the target are detected by the magnetic field sensing means.

23. The sensor according to claim 20, wherein the movement of the ferromagnetic target to a first position causes a vector of the magnetic field generated by the coil means to align substantially perpendicularly to the magnetic field sensing means which increases the magnetic field observed by the magnetic field sensing means, and further movement of the ferromagnetic target to a second position changes the magnetic field observed by the magnetic field sensing means.