Method and Apparatus for Magnetic Sensor Producing a Changing Magnetic Field

• US 20150022198A1
• Filed: 07/19/2013
• Published: 01/22/2015
• Est. Priority Date: 07/19/2013
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: David, Paul, Taylor, William P.
• Granted Patent: US 10,145,908 B2
• Time in Patent Office: Days
• US Class Current: 324/251
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence
• CPC Class Codes: G01R 33/00 Arrangements or instruments for measuring magnetic variables
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00

Abstract

Methods and apparatus for detecting a magnetic field include a semiconductor substrate, a coil configured to provide a changing magnetic field in response to a changing current in the coil; and a magnetic field sensing element supported by the substrate. The coil receives the changing current and, in response, generates a changing magnetic field. The magnetic field sensing element detects the presence of a magnetic target by detecting changes to the magnetic field caused by the target and comparing them to an expected value.

Claims

1. A magnetic field sensor comprising:

a semiconductor substrate;

a coil configured to provide a changing magnetic field in response to a changing current in the coil; and

a magnetic field sensing element supported by the substrate to sense the magnetic field as affected by the presence of a ferromagnetic target.

2. The magnetic field sensor of claim 1 wherein the coil is formed from at least one metal layer disposed on a surface of the substrate.

3. The magnetic field sensor of claim 1 wherein the magnetic field sensing element is a giant magnetoresistive (GMR) transducer.

4. The magnetic field sensor of claim 3 wherein the GMR transducer comprises a plurality of GMR elements in a bridge configuration.

5. The magnetic field sensor of claim 4 wherein a first pair of GMR elements of the H-bridge is positioned at an end of the coil and a second pair of GMR elements of the bridge is positioned at an opposing end of the coil.

6. The magnetic field sensor of claim 1 wherein at least a portion of the magnetic field sensing element is positioned within a loop of the coil.

7. The magnetic field sensor of claim 1 wherein the magnetic field sensing element is a Hall element.

8. The magnetic field sensor of claim 1 further including a current source coupled to the coil.

9. The magnetic field sensor of claim 1 further including a pulsed or transient current source coupled to the coil.

10. The magnetic field sensor of claim 1 wherein the coil is positioned above or below the substrate.

11. The magnetic field sensor of claim 1 wherein the coil is a separately formed element included in a same package with the substrate.

12. A method of detecting a magnetic field comprising:

providing a semiconductor substrate;

driving a changing current through a coil so that the coil generates an changing magnetic field; and

sensing, with a magnetic field sensing element supported by the substrate, variations in the changing magnetic field due to a proximity of a ferromagnetic target.

13. The method of claim 12 further comprising forming the inductive coil from one or more metal layers disposed on a surface of the substrate.

14. The method of claim 12 further comprising providing the magnetic field sensing element in the form of a plurality of GMR elements in an bridge configuration.

15. The method of claim 14 further comprising positioning a first pair of GMR elements of the bridge at an end of the inductive coil and positioning a second pair of GMR elements of the bridge at an opposing end of the inductive coil.

16. The method of claim 12 further comprising positioning at least a portion of the magnetic field sensing element within a loop of the inductive coil.

17. The method of claim 12 further comprising providing the magnetic field sensing element in the form of a Hall element

18. The method of claim 12 further comprising supplying a pulsed or transient current to the coil.

19. The method of claim 12 further comprising attaching the coil to a top or bottom surface of the substrate.

20. The method of claim 12 further comprising providing the coil as a separately formed element within a same package as the substrate.