Magnetic field sensor for detecting a magnetic field in any direction above thresholds

Patent metadata

Field	Value
Publication number	US-9664752-B2
Application number	US-201414277218-A
Country	US
Kind code	B2
Filing date	May 14, 2014
Priority date	May 24, 2013
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

A magnetic field sensor includes first, second, and third magnetic field sensing elements having respective first, second and third maximum response axes, the first second and third maximum response axes pointing along respective first, second, and third different coordinate axes. In response to a magnetic field, the first, second, and third magnetic field sensing elements are operable to generate first second, and third magnetic field signals. Signals representative of the first, second, and third magnetic field signals are compared with thresholds to determine if the magnetic field is greater than the thresholds. A corresponding method is also provided.

First claim

What is claimed is:

1. A magnetic field sensor, comprising:
first, second, and third magnetic field sensing elements having respective first, second and third maximum response axes, the first second and third maximum response axes pointing along respective first, second, and third different coordinate axes, wherein, in response to a magnetic field, the first, second, and third magnetic field sensing elements are operable to generate first second, and third magnetic field signals; and
an electronic circuit coupled to receive the first, second, and third magnetic field signals, wherein the electronic circuit comprises:
a threshold generator configured to generate first, second, and third operating point thresholds; and
a comparator circuit configured to compare signals corresponding to the first, second, and third magnetic field signals with the first, second, and third operating point thresholds, respectively, and to generate a comparator circuit output signal, wherein the comparator circuit output signal changes state to a first state if a respective one or more of the signals corresponding to the first, second, and third magnetic field signals has a magnitude above a respective one of the first, second, and third operating point thresholds.

2. The magnetic field sensor of claim 1 , wherein the electronic circuit is operable to cause the first, second, and third magnetic field sensing elements to generate the first second, and third magnetic field signals sequentially and with a sampling duty cycle less than about ten percent, and wherein substantial portions of the electronic circuit are placed in a lower power condition when the magnetic field signals are not being generated.

3. The magnetic field sensor of claim 1 , wherein the a comparator circuit comprises only two comparators.

4. The magnetic field sensor of claim 1 , wherein the comparator circuit output signal changes state to a second different state if a respective one or more of the signals corresponding to the first, second, and third magnetic field signals has a magnitude below a respective one of a first, second, and third release point thresholds, wherein the first, second, and third release point thresholds are related to and less than the first, second, and third operating point thresholds, respectively.

5. The magnetic field sensor of claim 1 , wherein the first, second, and third coordinate axes represent orthogonal Cartesian coordinates.

6. The magnetic field sensor of claim 1 , wherein the first magnetic field sensing element comprises a planar Hall element, the second magnetic field sensing element comprises a first vertical Hall element, and the third magnetic field sensing element comprises a second vertical Hall element.

7. The magnetic field sensor of claim 6 , wherein a respective one or more of the one or more comparator output signals changes state to a second different state if a respective one or more of the signals related to the first, second, and third magnetic field signals has a magnitude below a respective one of a first, second, and third release point threshold, wherein the first, second, and third release point thresholds are related to and less than the first, second, and third operating point thresholds, respectively.

8. The magnetic field sensor of claim 6 , wherein the electronic circuit further comprises a time divisional multiplexing module operable to time division multiplex the first, second, and third magnetic field sensing elements into a common circuit channel within the electronic circuit.

9. The magnetic field sensor of claim 8 , wherein the first, second, and third magnetic field sensing elements are chopped, and wherein the common circuit channel comprises a switched capacitor notch filter having a first notch at a frequency selected to remove products of the chopping.

10. The magnetic field sensor of claim 6 , wherein the electronic circuit further comprises a magnetic field sensing element drive circuit operable to time division multiplex drive signals applied to the first, second, and third magnetic field sensing elements.

11. The magnetic field sensor of claim 6 , wherein the electronic circuit further comprises a sensitivity adjust memory configured to store first, second, and third sensitivity correction values associated with sensitivities of the first, second, and third magnetic field sensing elements, respectively, wherein the magnetic field sensor is operable to apply the first, second, and third sensitivity correction values to match sensitivities of the signals related to the first, second, and third magnetic field signals, respectively.

12. The magnetic field sensor of claim 6 , wherein the electronic circuit further comprises an offset adjust memory configured to store first, second, and third offset correction values associated with offsets of the first, second, and third magnetic field sensing elements, respectively, wherein the magnetic field sensor is operable to apply the first, second, and third offset correction values to match offsets of the signals related to the first, second, and third magnetic field signals, respectively.

13. The magnetic field sensor of claim 6 , wherein the electronic circuit further comprises a threshold memory configured to store first, second, and third threshold values for comparison with signals representative of the first, second, and third magnetic field signals, respectively.

14. The magnetic field sensor of claim 1 , wherein the first magnetic field sensing element comprises a planar Hall element, the second magnetic field sensing element comprises a first magnetoresistance circuit, and the third magnetic field sensing element comprises a second magnetoresistance circuit.

15. The magnetic field sensor of claim 14 , wherein a respective one or more of the one or more comparator output signals changes state to a second different state if a respective one or more of the signals related to the first, second, and third magnetic field signals has a magnitude below a respective one of a first, second, and third release point threshold, wherein the first, second, and third release point thresholds are related to and less than the first, second, and third operating point thresholds, respectively.

16. The magnetic field sensor of claim 14 , wherein the electronic circuit further comprises a time divisional multiplexing module operable to time division multiplex the first, second, and third magnetic field sensing elements.

17. The magnetic field sensor of claim 14 , wherein the first magnetic field sensing element is chopped with a chopping frequency of Fchop, and wherein the electronic circuit comprises a switched capacitor notch filter coupled to the first magnetic field sensing element and having a first notch at a frequency of Fchop.

18. The magnetic field sensor of claim 14 , wherein the electronic circuit further comprises a magnetic field sensing element drive circuit operable to time division multiplex drive signals applied to the first, second, and third magnetic field sensing elements.

19. The magnetic field sensor of claim 14 , wherein the electronic circuit further comprises a sensitivity adjust memory configured to store first, second, and third sensitivity correction values associated with sensitivities of the first, second, and third magnetic field sensing elements, respectively, wherein the magnetic field sensor is operable to apply the first, second, and third sensitivity correction values to match sensitivities of the signals related to the first, second, and third magnetic field signals, r

Assignees

• Allegro Microsystems Llc

Inventors

• Monreal Gerardo A
• Uberti Bruno Luis

Classifications

• G01R33/0023 Primary

  Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration (G01R33/0017 takes precedence) · CPC title

• G01R33/07 Primary

  Hall effect devices · CPC title

• G01R33/0206

  Three-component magnetometers · CPC title