Magnetoresistive sensor with compensating coil

1. A magnetoresistive sensor, comprising:

a silicon substrate;

a collection of MR sensor units on the silicon substrate;

a collection of rectangular soft ferromagnetic flux concentrators in a parallel arrangement, wherein adjacent ones of the soft ferromagnetic flux concentrators define a gap between the adjacent ones of the soft ferromagnetic flux concentrators, and the MR sensor units are directly below the gaps;

a serpentine compensating coil above the MR sensor units and below the gap between the adjacent ones of the soft ferromagnetic flux concentrators, the serpentine compensation coil having parallel linear segments, the parallel linear segments including a corresponding linear segment under corresponding ones of the soft ferromagnetic flux concentrators and the gaps, wherein the serpentine compensating coil is configured for current to flow in a first direction in the linear segments under each of the soft ferromagnetic flux concentrators and in a second direction opposite the first direction under each of the gaps;

a connecting circuit interconnecting the MR sensor unites to form a push-pull sensor bridge;

a collection of lead pads used for electrical connections to the serpentine compensating coil and the push-pull bridge; and

an encapsulation structure configured to cover the push-pull sensor bridge and the serpentine compensation coil.

2. The magnetoresistive sensor according to claim 1 ,

wherein the magnetoresistive sensor is placed on a PCB substrate to form a sensor chip,

wherein the PCB substrate comprises a spiral initialization coil,

wherein the sensor chip is the spiral initialization coil, and

wherein the direction of a current flowing through the spiral initialization coil is parallel to the direction of a sensitive axis of the sensor chip.

3. The magnetoresistive sensor according to claim 2 ,

wherein the PCB substrate further comprises lead pads and conductive traces which are used to interconnect the MR sensor units to form the push-pull sensor bridge,

wherein these lead pads are disposed at the bottom of the PCB substrate while the sensor chips and the lead pads at the top of the PCB substrate are encapsulated using plastic or resin.

4. The magnetoresistive sensor according to claim 1 , wherein the push-pull sensor bridge is a push-pull full bridge circuit.

5. The magnetoresistive sensor according to claim 1 , wherein the magnetoresistive sensor has an LGA encapsulation structure.

6. The magnetoresistive sensor according to claim 1 , comprising an application-specific integrated circuit (ASIC), wherein the ASIC is electrically connected to the push-pull sensor bridge.

7. The magnetoresistive sensor according to claim 1 , wherein the magnetoresistive sensor is disposed on a lead frame.

8. The magnetoresistive sensor according to claim 7 , wherein the lead frame is encapsulated in plastic.

9. The magnetoresistive sensor according to claim 1 , further comprising:

a first insulation layer;

a second insulation layer; and

a passivation layer,

wherein the collection of MR sensor units is covered with the first insulation layer,

wherein the serpentine compensating coil is covered with the second insulation layer, and

wherein the passivation layer is deposited on the entire sensor chip.

10. A magnetoresistive sensor, comprising:

a silicon substrate;

a push-pull sensor bridge, the sensor bridge including a plurality of MR sensor units on the silicon substrate;

a first insulation layer over the plurality of MR sensor units;

a serpentine compensating coil on the first insulating layer;

a second insulating layer over the compensation coil;

a plurality of flux concentrators comprising a soft ferromagnetic material, the flux concentrators having a rectangular shape with a long axis and being in a parallel arrangement to define gaps between adjacent ones of the flux concentrators, wherein the gaps are directly over the MR sensor units; and

lead pads configured to provide electrical connections to the compensation coil and the sensor bridge,

wherein the compensation coil includes parallel conductor segments, the parallel conductor segments being parallel to the long axes of the flux concentrators, wherein corresponding ones of the conductor segments are under corresponding ones of the flux concentrators and the gaps, and

wherein the parallel conductor segments are electrically-connected to enable current flowing in the compensation coil to flow in a first direction under the flux concentrators and in an opposite second direction under the gaps.

11. The magnetoresistive sensor according to claim 10 ,

wherein the magnetoresistive sensor is placed on a PCB substrate to form a sensor chip,

wherein the PCB substrate comprises a spiral initialization coil,

wherein the sensor chip is the spiral initialization coil, and

wherein the direction of a current flowing through the spiral initialization coil is parallel to the direction of a sensitive axis of the sensor chip.

12. The magnetoresistive sensor according to claim 10 , wherein the push-pull sensor bridge is a push-pull full bridge circuit.

13. The magnetoresistive sensor according to claim 10 , wherein the magnetoresistive sensor has an LGA encapsulation structure.

14. The magnetoresistive sensor according to claim 10 , comprising an application-specific integrated circuit (ASIC), wherein the ASIC is electrically connected to the push-pull sensor bridge.