Magnetic field sensor with 3-axes self test

Patent metadata

Field	Value
Publication number	US-10012707-B2
Application number	US-201615140137-A
Country	US
Kind code	B2
Filing date	Apr 27, 2016
Priority date	Apr 29, 2015
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A magnetic field sensor includes built-in self-test coils in a configuration to provide magnetic field stimulation along three axes, with a high field factor, and thus, reduce a power budget of the sensor and physical size of the self-test coils. The magnetic field sensor comprises a first bridge circuit including a plurality of sense elements configured to sense a magnetic field. The magnetic field sensor further comprises re-configurable self-test current lines coupled to a self-test source to perform high field, high power wafer and die level testing and trim, as well as low power in-situ characterization and calibration of the sensor. The self-test current lines may be routed to form a coil with multiple turns around the TMR elements.

First claim

What is claimed is:

1. A magnetic field sensor, comprising:
a plurality of magnetoresistance sense elements coupled together as a bridge circuit to sense a magnetic field; and
a first circuit comprising a first plurality of current lines, wherein the first plurality of current lines is configured to selectively conduct current in a series configuration and in a parallel configuration, wherein the first circuit includes circuitry to selectively energize the first plurality of current lines in series in a first instance and in parallel in a second instance, wherein each current line of the first plurality of current lines is adjacent to a magnetoresistance sense element of the plurality of magnetoresistance sense elements, wherein, when energized, at least one current line of the first plurality of current lines is configured to generate an induced magnetic field sensed by the bridge circuit, and wherein the first circuit is configured to selectively energize, in series in the first instance and in parallel in the second instance, the at least one current line and another current line of the first plurality of current lines of the first circuit.

2. The magnetic field sensor of claim 1 , wherein the at least one current line and the another current line includes the entirety of the first plurality of current lines.

3. The magnetic field sensor of claim 1 , wherein one or more current lines of the first plurality of current lines are routed to form a coil around at least one magnetoresistance sense element of the plurality of magnetoresistance sense elements.

4. The magnetic field sensor of claim 1 , wherein one or more current lines of the first plurality of current lines are routed to form a coil extending across at least one magnetoresistance sense element of the plurality of magnetoresistance sense elements.

5. The magnetic field sensor of claim 1 , wherein one or more current lines of the first plurality of current lines are routed to form a loop around at least one magnetoresistance sense element of the plurality of magnetoresistance sense elements.

6. The magnetic field sensor of claim 1 , wherein each magnetoresistance sense element of the plurality of magnetoresistance sense elements includes a first ferromagnetic layer and a second ferromagnetic layer separated by a non-magnetic, insulating barrier, and
wherein the first ferromagnetic layer of each magnetoresistance sense element includes a magnetization direction free to rotate in a magnetic field, and wherein the second ferromagnetic layer of each magnetoresistance sense element includes a fixed magnetization direction.

7. The magnetic field sensor of claim 1 , wherein the plurality of magnetoresistance sense elements includes one or more tunneling magnetoresistance sense elements, giant magnetoresistance sense elements, and/or anisotropic magnetoresistance sense elements.

8. The magnetic field sensor of claim 1 , further comprising:
a current source connection that connects a current source to the first circuit for selectively energizing the at least one current line of the first plurality of current lines.

9. The magnetic field sensor of claim 1 , further comprising:
a second circuit comprising a second plurality of current lines, wherein each current line of the second plurality of current lines is adjacent to a magnetoresistance sense element of the plurality of magnetoresistance sense elements;
a first current source connection that connects a first current source to the first circuit; and
a second current source connection that connects a second current source to the second circuit.

10. The magnetic field sensor of claim 1 , wherein at least one magnetoresistance sense element of the plurality of magnetoresistance sense elements includes at least one flux guide.

11. The magnetic field sensor of claim 10 , wherein the at least one flux guide is a vertical bar comprising a high permeability magnetic material with an end terminating proximate to an edge of the respective magnetoresistance sense element.

12. The magnetic field sensor of claim 10 , wherein the at least one flux guide is located below the respective magnetoresistance sense element.

13. The magnetic field sensor of claim 1 , further comprising:
a second plurality of magnetoresistance sense elements coupled together as a second bridge circuit to sense a magnetic field; and
a second circuit comprising a second plurality of current lines, wherein each current line of the second plurality of current lines is adjacent to a magnetoresistance sense element of the second plurality of magnetoresistance sense elements, wherein, when energized, at least one current line of the second plurality of current lines is configured to generate a second induced magnetic field sensed by the second bridge circuit, and wherein the second circuit is configured to selectively energize, in parallel or in series, the at least one current line and another current line of the second plurality of current lines of the second circuit,
wherein the first bridge circuit is configured to sense the magnetic field in a first direction, and the second bridge circuit is configured to sense the magnetic field in a second direction that is orthogonal to the first direction.

14. The magnetic field sensor of claim 13 , wherein the second direction extends out of a plane formed by the second plurality of magnetoresistance sense elements.

15. The magnetic field sensor of claim 13 , further comprising:
a third plurality of magnetoresistance sense elements coupled together as a third bridge circuit to sense a magnetic field in a third direction, wherein the third direction is orthogonal to the first and second directions; and
a third circuit comprising a third plurality of current lines, wherein each current line of the third plurality of current lines is adjacent to a magnetoresistance sense element of the third plurality of magnetoresistance sense elements, wherein, when energized, at least one current line of the third plurality of current lines is configured to generate a third induced magnetic field sensed by the third bridge circuit, and wherein the third circuit is configured to selectively energize, in parallel or in series, the at least one current line and another current line of the third plurality of current lines of the third circuit.

16. A magnetic field sensor, comprising:
a plurality of magnetoresistance sense elements coupled together as a bridge circuit to sense a magnetic field in a first direction;
a first circuit comprising a first plurality of current lines, wherein each current line of the first plurality of current lines is adjacent to a magnetoresistance sense element of the plurality of magnetoresistance sense elements, wherein, when energized, at least one current line of the first plurality of current lines is configured to generate an induced magnetic field sensed by the bridge circuit, and wherein the induced magnetic field includes an in-plane component and an out-of-plane component, and
at least one flux guide, wherein the at least one flux guide is a vertical bar comprising a high permeability magnetic material with an end terminating proximate to an edge of at least one magnetoresistance sense element of the plurality of magnetoresistance sense elements, wherein the at least one flux guide is located between the at least one current line and another current line of the plurality of current lines, and wherein, when the at least one current line and the another current line of the plurality of current lines are energized, the in-plane component of the induced magnetic field at the at

Assignees

• Everspin Technologies Inc

Inventors

• Mather Phillip G
• Mohan Anuraag
• De Sandre Guido

Classifications

• G01R33/0206

  Three-component magnetometers · CPC title

• G01R33/0011

  comprising means, e.g. flux concentrators, flux guides, for guiding or concentrating the magnetic flux, e.g. to the magnetic sensor · CPC title

• G01R33/098 Primary

  comprising tunnel junctions, e.g. tunnel magnetoresistance sensors · CPC title

• G01R33/0023

  Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration (G01R33/0017 takes precedence) · CPC title