Methods and apparatus for magnetic sensors having highly uniform magnetic fields

Patent metadata

Field	Value
Publication number	US-10215550-B2
Application number	US-201213461164-A
Country	US
Kind code	B2
Filing date	May 1, 2012
Priority date	May 1, 2012
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

Methods and apparatus for a magnetic sensor including an elliptical magnet to generate substantially circular concentric zones of similar flux density in a plane over and parallel to a surface of the magnet. The sensor can include a sensing element disposed a selected distance from the magnet and a substrate containing circuitry to process a signal from the sensing element to provide a sensor output.

First claim

What is claimed is:

1. A system, comprising:
a magnet having a length, width, and height, wherein the magnet has a substantially planar surface that defines an ellipse across the length and width to generate substantially circular concentric zones of similar flux density in a plane over and parallel to the elliptical planar surface of the magnet, wherein the ellipse is noncircular; and
a magnetic sensor IC package comprising:
a sensing element disposed a selected distance from the planar surface of the magnet, wherein the planar surface of the magnet and a surface of the magnetic sensor IC package define an airgap with respect to rotation of the magnetic sensor IC package and/or magnet, wherein a center of the sensing element is substantially aligned with a center of the magnet; and

a substrate containing circuitry to process a signal from the sensing element to provide an output of the magnetic sensor IC package.

2. The magnetic sensor IC package according to claim 1 , wherein a center of the concentric zones is aligned with a center of the magnet surface.

3. The magnetic sensor IC package according to claim 1 , wherein a gradient of the flux density across the concentric zones is less than for a cylindrical magnet of the same volume.

4. The magnetic sensor IC package according to claim 1 , wherein the magnetic sensor IC package provides better accuracy than a magnetic sensor having a cylindrical magnet having the same volume as the elliptical magnet.

5. The magnetic sensor IC package according to claim 1 , wherein the sensing element comprises a circular vertical hall element.

6. The magnetic sensor IC package according to claim 1 , wherein a length to width ratio of the elliptical magnet surface is about 1.5.

7. The magnetic sensor IC package according to claim 1 , wherein the elliptical magnet is not keyed for orientation.

8. The magnetic sensor IC package according to claim 1 , wherein the magnetic sensor IC package senses angular position of a target.

9. The magnetic sensor IC package according to claim 1 , wherein the sensing element comprises at least one of a Hall element, an anisotropic magnetoresistance (AMR) element and/or a giant magnetoresistance (GMR) element.

10. The magnetic sensor IC package according to claim 9 , wherein the sensing element comprises a circular vertical hall element.

11. A system, comprising:
a magnet having a length, width, and height, wherein the magnet has a substantially planar surface that defines a noncircular ellipse to generate substantially circular concentric zones of substantially similar flux density in a plane parallel to the elliptical planar surface of the magnet; and
magnetic sensor IC package comprising
a circular implant region having a plurality of vertical Hall elements defining a center, wherein the Hall elements are located in a plane located a distance from the elliptical planar surface of the magnet, wherein the center of the vertical Hall elements is substantially aligned with a center of the elliptical planar surface of the magnet.

12. The magnetic sensor IC package according to claim 11 , wherein a gradient of the flux density across the concentric zones is less than for a cylindrical magnet of the same volume.

13. The magnetic sensor IC package according to claim 11 , wherein the sensor provides better accuracy than a magnetic sensor having a cylindrical magnet having the same volume as the elliptical magnet.

14. The magnetic sensor IC package according to claim 11 , wherein a length to width ratio of the elliptical magnet is about 1.5.

15. The magnetic sensor IC package according to claim 11 , wherein the elliptical magnet is not keyed for orientation.

Assignees

• Metivier Ryan
• Taylor William P
• Allegro Microsystems Llc

Inventors

• Metivier Ryan
• Taylor William P

Classifications

• G01B7/30 Primary

  for measuring angles or tapers; for testing the alignment of axes · CPC title