Methods and apparatus for magnetic sensor having integrated coil

1. A magnetic field sensor, comprising:

a die;

a coil proximate the die to generate a magnetic field;

a Hall element magnetic field sensing element on said die to detect changes in the magnetic field generated by the coil as a result of movement of a ferromagnetic target external to the magnetic field sensor;

a constant current source coupled to the coil such that alignment changes of the magnetic field generated by the coil with respect to the magnetic sensing element caused by movement of the target are detected by the magnetic field sensing element,

wherein the movement of the ferromagnetic target to a first position causes a vector of the magnetic field generated by the coil to align substantially perpendicularly to the magnetic field sensing element which increases the magnetic field observed by the magnetic field sensing element, and further movement of the ferromagnetic target to a second position changes the magnetic field observed by the magnetic field sensing element; and

a GMR magnetic sensing element positioned in relation to the coil, wherein the Hall element magnetic sensing element is configured for a first airgap distance, and the GMR magnetic sensing element is configured for a second airgap distance, which is greater than the first airgap distance.

2. The sensor according to claim 1 , wherein the coil is integrated with the die.

3. The sensor according to claim 1 , wherein the coil is substantially flat.

4. The sensor according to claim 1 , wherein the coil comprises a solenoid.

5. The sensor according to claim 1 , wherein the only a portion of the Hall magnetic field sensing element overlaps with the coil.

6. The sensor according to claim 1 , wherein the Hall magnetic field sensing element is positioned at least in part between the coil and the die.

7. The sensor according to claim 1 , wherein the coil is positioned at least in part between the Hall magnetic field sensing element and the die.

8. The sensor according to claim 1 , wherein about half of an area of the Hall magnetic field sensing element overlaps with the coil.

9. The sensor according to claim 1 , wherein about half of a length of the Hall magnetic field sensing element overlaps with the coil.

10. The sensor according to claim 1 , wherein sensor includes a further magnetic field sensing element.

11. The sensor according to claim 1 , wherein the die includes circuitry to process information from the Hall magnetic field sensor.

12. The sensor according to claim 1 , wherein the Hall magnetic field sensing element has at least a portion that overlaps the coil.

13. The sensor according to claim 1 , wherein the GMR magnetic field sensing element comprises a semiconductor device.

14. A magnetic field sensor, comprising:

a die;

a first means proximate the die for generating a magnetic field, wherein the first means comprises a coil; and

a second means for detecting changes in the magnetic field generated by the first means as a result of movement of a ferromagnetic target external to the magnetic field sensor, wherein the second means comprises a Hall element magnetic sensing element;

a constant current source means coupled to the first means such that alignment changes of the magnetic field generated by the coil with respect to the Hall magnetic sensing element caused by movement of the target are detected by the Hall magnetic field sensing element,

wherein the movement of the ferromagnetic target to a first position causes a vector of the magnetic field generated by the coil to align substantially perpendicularly to the Hall magnetic field sensing element, which increases the magnetic field observed by the Hall magnetic field sensing element, and further movement of the ferromagnetic target to a second position changes the magnetic field observed by the Hall magnetic field sensing element, and

and a GMR magnetic sensing element positioned in relation to the coil, wherein the Hall element magnetic sensing element is configured for a first airgap distance, and the GMR magnetic sensing element is configured for a second airgap distance, which is greater than the first airgap distance.

15. The sensor according to claim 14 , wherein the first means is integrated with the die.

16. A method, comprising:

providing a die within a magnetic field sensor;

providing a coil proximate the die to generate a magnetic field;

providing a Hall element magnetic field sensing element to detect changes in the magnetic field generated by the coil as a result of movement of a ferromagnetic target external to the magnetic field sensor;

coupling a constant current source to the coil such that alignment changes of the magnetic field generated by the coil with respect to the magnetic sensing element caused by movement of the target are detected by the magnetic field sensing element,

wherein the movement of the ferromagnetic target to a first position causes a vector of the magnetic field generated by the coil to align substantially perpendicularly to the magnetic field sensing element, which increases the magnetic field observed by the magnetic field sensing element, and further movement of the ferromagnetic target to a second position changes the magnetic field observed by the magnetic field sensing element; and

providing a GMR magnetic sensing element positioned in relation to the coil, wherein the Hall element magnetic sensing element is configured for a first airgap distance, and the GMR magnetic sensing element is configured for a second airgap distance, which is greater than the first airgap distance.

17. The method according to claim 16 , wherein the coil is integrated on the die.

18. The method according to claim 16 , wherein the GMR magnetic field sensing element is positioned at least in part between the coil and the die.

19. The method according to claim 16 , wherein the coil is positioned at least in part between the GMR magnetic field sensing element and the die.

20. The method according to claim 16 , wherein the GMR magnetic field sensing element has at least a portion that overlaps the coil.

21. A magnetic field sensor, comprising:

a die;

a coil proximate the die to generate a magnetic field, wherein the coil is integrated with the die;

a GMR magnetic field sensing element on said die to detect changes in the magnetic field generated by the coil as a result of movement of a ferromagnetic target external to the magnetic field sensor, wherein the die includes circuitry to process information from the magnetic field sensing element;

a constant current source coupled to the coil such that alignment changes of the magnetic field generated by the coil with respect to the magnetic sensing element caused by movement of the target are detected by the magnetic field sensing element,

wherein the movement of the ferromagnetic target causes a vector of the magnetic field generated by the coil to align substantially parallel to the magnetic field sensing element; and

a Hall magnetic sensing element positioned in relation to the coil, wherein the Hall element magnetic sensing element is configured for a first airgap distance, and the GMR magnetic sensing element is configured for a second airgap distance, which is greater than the first airgap distance.

22. The sensor according to claim 21 , wherein the only a portion of the GMR magnetic field sensing element overlaps with the coil.

23. The sensor according to claim 21 , wherein the GMR magnetic field sensing element is positioned at least in part between the coil and the die.

24. The sensor according to claim 21 , wherein the coil is positioned at least in part between the GMR magnetic field sensing element and the die.

25. A magnetic field sensor, comprising:

a die;

a coil proximate the die to generate a magnetic field;

a GMR magnetic field sensing element on said die to detect changes in the magnetic field generated by the coil as a result of movement of a ferromagnetic target external to the magnetic field sensor;

a constant current source coupled to the coil such that alignment changes of the magnetic field generated by the coil with respect to the GMR magnetic sensing element caused by movement of the target are detected by the GMR magnetic field sensing element,

wherein the movement of the ferromagnetic target to a first position causes a vector of the magnetic field generated by the coil to align substantially perpendicularly to the GMR magnetic field sensing element which increases the magnetic field observed by the GMR magnetic field sensing element, and further movement of the ferromagnetic target to a second position changes the magnetic field observed by the GMR magnetic field sensing element; and

a Hall magnetic sensing element positioned in relation to the coil, wherein the Hall element magnetic sensing element is configured for a first airgap distance, and the GMR magnetic sensing element is configured for a second airgap distance, which is greater than the first airgap distance.