Single chip push-pull bridge-type magnetic field sensor
First Claim
1. A single-chip push-pull magnetoresistive sensor bridge, comprisinga 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;
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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.
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Citations
17 Claims
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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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. - View Dependent Claims (11, 12, 13, 14)
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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 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. - View Dependent Claims (16, 17)
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Specification