Single chip push-pull bridge-type magnetic field sensor

Patent metadata

Field	Value
Publication number	US-9664754-B2
Application number	US-201214009912-A
Country	US
Kind code	B2
Filing date	Apr 1, 2012
Priority date	Apr 6, 2011
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

The present invention discloses a design of a single-chip push-pull bridge sensor, composed of magnetoresistive elements, utilizing on-chip permanent magnets. The permanent magnets are oriented to preset magnetization directions of free layers of adjacent sensor bridge arms so that they point to different directions with respect the same sensing direction, enabling push-pull operation. The push-pull bridge sensor of the present invention is integrated on a single chip. Additionally, an on-chip coil is disclosed to reset or calibrate the magnetization directions of the free layers of the magnetoresistive elements.

First claim

The invention claimed is:

1. A single-chip push-pull magnetoresistive sensor bridge, comprising
a sensor bridge comprised of magnetoresistive sensor arms, wherein each magnetoresistive sensor arm comprises multiple magnetic tunnel junction (MTJ) or giant magnetoresistance (GMR) magnetoresistive elements, each of the magnetoresistive elements has a magnetic pinned layer that has a same pinned layer magnetization direction as the other magnetoresistive elements, each of the magnetoresistive elements has a free layer that has a magnetization direction, and each of the magnetoresistive elements is sensitive to a magnetic field along a sensing direction that is perpendicular to the pinned layer magnetization direction; and
permanent magnets disposed on two sides of each of the magnetoresistive sensor arms to bias the direction of the magnetization of the multiple magnetoresistive elements in each of the magnetoresistive sensor arms, wherein the permanent magnets are oriented to provide for each sensor arm a magnetic bias used to preset the magnetization direction of the free layer for the respective sensor arm, and the permanent magnets provide magnetic biases in different directions for adjacent sensor arms to preset the magnetization direction of the free layer for adjacent sensor arms in different directions, the preset magnetization direction of the free layer for adjacent sensor arms being either a sharp angle or obtuse angle with respect to the sensing direction such that the preset magnetization is not aligned with either of the sensing direction or the pinned layer magnetization direction.

2. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 1 , wherein the length of each permanent magnet is larger than the gap between adjacent permanent magnets in order to make the magnetic field between the permanent magnets uniform.

3. A single-chip push-pull bridge magnetoresistive sensor as claimed in claim 1 , wherein a first sensor arm has a preset magnetization of direction that has a first rotational angle from the sensing direction, and the second sensor arm has a preset magnetization direction that has a second rotational angle from the sensing direction that is equal in magnitude and opposite in direction from the first rotational angle.

4. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 1 , wherein each magnetoresistive element has a shape anistropy, and for each sensor arm the preset magnetization direction is determined by the shape anistropy of the magnetoresistive elements in the sensor arm and a direction of the magnetic bias provided by the permanent magnets disposed on the two sides of the sensor arm.

5. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 1 , wherein the magnitude of the magnetic bias field is dependent on the thickness of the permanent magnets.

6. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 1 , wherein each of the pair of the permanent magnets disposed on two sides of a magnetoresistive element has an edge closest to the magnetoresistive element, and the strength of the permanent magnet bias field can be adjusted by varying the orientation of the magnetization directions of the permanent magnets or the angle of the edge boundary with respect to the sensing direction.

7. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 1 , wherein the bias field provided by the permanent magnets is uniform.

8. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 1 , wherein the magnetoresistive elements are parallel to each other.

9. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 1 , further comprising an electric coil in the vicinity of the magnetoresistive elements, wherein there is an insulation layer between the magnetoresistive elements and the electric coil.

10. A single-chip push-pull magnetoresistive sensor bridge, comprising
a sensor bridge comprised of magnetoresistive sensor arms, each magnetoresistive sensor arm comprising a string of MTJ elements, each of the MTJ elements has a magnetic pinned layer that has a same pinned layer magnetization direction as the other MTJ elements, each of the MTJ elements have a free layer that has a magnetization direction, and each of the MTJ elements is sensitive to a magnetic field along a sensing direction that is perpendicular to the pinned layer magnetization direction; and
permanent magnet bars disposed on two sides of each string of MTJ elements to bias the direction of the magnetization of each MTJ element in the string of MTJ elements, wherein the permanent magnet bars are oriented to provide for each sensor arm a magnetic bias used to preset the magnetization direction of the free layer for the respective sensor arm, and the permanent magnet bars provide magnetic biases for adjacent sensor arms in different directions to preset the magnetization direction of the free layer for adjacent sensor arms in different directions, the preset magnetization direction of the free layer for adjacent sensor arms being either a sharp angle or obtuse angle with respect to the sensing direction such that the preset magnetization is not aligned with either of the sensing direction or the pinned layer magnetization direction.

11. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 10 , wherein the permanent magnet bars is a pair of permanent magnet bars on opposing sides of each string of MTJ elements.

12. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 11 , wherein the pair of permanent magnet bars are parallel to each other, forming a gap between the pair of permanent magnet bars, wherein each of the pair of permanent magnet bars has a length longer than the gap.

13. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 10 , further comprising bonding pads.

14. A single-chip push-pull magnetoresistive sensor bridge as claimed in claim 10 , further comprising an electric coil in the vicinity of the magnetoresistive elements, wherein there is an insulation layer between the magnetoresistive elements and the electric coil.

15. A single-chip push-pull magnetoresistive sensor bridge, comprising
a sensor bridge comprised of magnetoresistive sensor arms, each magnetoresistive sensor arm comprising a string of series-connected MTJ elements, each of the MTJ elements has a magnetic pinned layer that has a same pinned layer magnetization direction as the other MTJ elements, each of the MTJ elements have a free layer that has a magnetization direction, and each of the MTJ elements is sensitive to a magnetic field along a sensing direction that is perpendicular to the pinned layer magnetization direction; and
a plurality of permanent magnet bars, including a pair of parallel permanent magnet bars proximate to each string of MTJ elements, the pair of parallel permanent magnet bars forming a gap between the pair of parallel permanent magnet bars within which is the string of series-connected MTJ elements, wherein each of the pair of parallel permanent magnet bars has a length longer than the gap to uniformly bias the direction of the magnetization of each MTJ element in the string of MTJ elements, wherein the permanent magnet bars are oriented to provide for each sensor arm a magnetic bias used to preset the magnetization direction of the free layer for the respective sensor arm, and the permanent magnet bars provide magnetic biases for adjacent sensor arms in different directions to preset the magnetization direction of the free layer for adjacent sensor ar

Assignees

• Jin Insik
• Lei Xiaofeng
• Deak James Geza
• Shen Weifeng
• Xue Songsheng
• Li Wei
• Multidimension Technology Co Ltd

Inventors

• Jin Insik
• Lei Xiaofeng
• Deak James Geza
• Shen Weifeng
• Xue Songsheng
• Li Wei

Classifications

• G01R33/0005

  Geometrical arrangement of magnetic sensor elements; Apparatus combining different magnetic sensor types (G01R33/0206 takes precedence) · CPC title

• G06Q10/00

  Administration; Management · CPC title

• G06Q2220/00

  Business processing using cryptography · 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

• G07F1/00

  Coin inlet arrangements; Coins specially adapted to operate coin-freed mechanisms · CPC title