Circuits and Methods for Self-Calibrating or Self-Testing a Magnetic Field Sensor Using Phase Discrimination

• US 20150301149A1
• Filed: 04/17/2014
• Published: 10/22/2015
• Est. Priority Date: 04/17/2014
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Cesaretti, Juan Manuel, Milesi, Alejandro G., Romero, Hernan D., Uberti, Bruno Luis, Alpago, Octavio, Martin Pirchio, Franco Noel
• Granted Patent: US 9,645,220 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: G01R 33/075 Hall devices configured for spinning current measurements
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

A magnetic field sensor has a reference magnetic field channel and an external magnetic field channel. The magnetic field sensor uses phase discrimination to isolate a reference-magnetic-field signal component from an external magnetic field signal component in the two channels.

Claims

1. A magnetic field sensor, comprising:

a reference magnetic field generator, wherein the reference magnetic field generator is configured to generate an AC reference magnetic field having a first frequency with a first phase;

a magnetic field sensing circuit comprising at least one magnetic field sensing element, wherein the magnetic field sensing circuit is configured to generate a combined output signal responsive to the AC reference magnetic field and also responsive to an external magnetic field; and

a signal processing circuit coupled to receive the combined output signal, wherein the signal processing circuit comprises a first modulator, wherein the first modulator is configured to modulate the combined signal with the same first frequency as the reference magnetic field generator but with a second different phase to generate a modulated combined signal.

2. The magnetic field sensor of claim 1, wherein a difference between the first phase and the second different phase is ninety degrees.

3. The magnetic field sensor of claim 1, further comprising:

a reference modulator coupled to receive a current signal and configured to modulate the current signal to generate a modulated current signal having the first frequency; and

at least one coil disposed proximate to the at least one magnetic field sensing element, the at least one coil coupled to receive the modulated current signal and configured to generate the AC reference magnetic field.

4. The magnetic field sensor of claim 1, wherein the signal processing circuit is further configured to generate a reference field signal responsive to the AC reference magnetic field and not responsive to the external magnetic field and, at the same time, configured to generate an external field signal responsive to the external magnetic field and not responsive to the AC reference magnetic field.

5. The magnetic field sensor of claim 1, wherein the signal processor circuit comprises:

a first circuit channel, the first circuit channel comprising a second modulator coupled to the first modulator and configured to generate, at baseband, an external field signal responsive to the external magnetic field and not responsive to the AC reference magnetic field, wherein the second modulator is configured to modulate the modulated combined signal; and

a second circuit channel, the second circuit channel comprising a third modulator coupled to the first modulator and configured to generate, at baseband, a reference field signal responsive to the AC reference magnetic field and not responsive to the external magnetic field, wherein magnetic field sensor is operable to generate the external field signal and the reference field signal at the same time, wherein the third modulator is configured to modulate the modulated combined signal.

6. The magnetic field sensor of claim 5, wherein the second modulator is configured to modulate the modulated combined signal with the same first frequency as the reference magnetic field generator, and wherein the third modulator is configured to modulate the modulated combined signal with a frequency different from first frequency.

7. The magnetic field sensor of claim 5, further comprising a feedback circuit coupled to the second circuit channel and configured to generate a feedback signal coupled to at least one of the magnetic field sensing circuit or the signal processing circuit to control an amplitude of the external field signal according to an amplitude of the reference field signal.

8. The magnetic field sensor of claim 7, wherein the feedback circuit is configured to correct error fluctuations in a transfer characteristic of the magnetic field sensing circuit.

9. The magnetic field sensor of claim 1, wherein the at least one magnetic field sensing element comprises first and second magnetic field sensing elements coupled so as to constructively combine output signals therefrom.

10. The magnetic field sensor of claim 1, wherein the at least one magnetic field sensing element comprises first and second magnetoresistance elements coupled so as to constructively combine output signals therefrom.

11. The magnetic field sensor of claim 1, wherein the at least one magnetic field sensing element comprises first and second Hall elements coupled so as to constructively combine output signals therefrom, wherein the first and second Hall elements are driven in respective coupling arrangements representative of current spinning phases that are ninety degrees apart.

12. The magnetic field sensor of claim 1, wherein the at least one magnetic field sensing element comprises first and second Hall elements coupled so as to constructively combine output signals therefrom, wherein the first and second Hall elements are driven in respective coupling arrangements representative of current spinning phases that are the same.

13. The magnetic field sensor of claim 1, wherein the at least one magnetic field sensing element comprises at least one Hall element, wherein the magnetic field sensor further comprises:

a current spinning module coupled to the at least one Hall element and configured to current spin the at least one Hall element by redirecting drive currents to, and redirecting output connections to, different nodes of the at least one Hall element at a spinning rate having a spinning frequency.

14. The magnetic field sensor of claim 13, wherein the at least one magnetic field sensing element comprises first and second Hall elements coupled so as to constructively combine output signals therefrom, wherein the first and second Hall elements are driven in respective coupling arrangements representative of current spinning phases that are ninety degrees apart.

15. A method used on a magnetic field sensor, the method comprising:

generating an AC reference magnetic field having a first frequency with a first phase;

generating, with one or more magnetic field sensing elements, a combined output signal responsive to the AC reference magnetic field and also responsive to an external magnetic field; and

modulating the combined signal with the same first frequency as the reference magnetic field generator but with a second different phase to generate a modulated combined signal.

16. The method of claim 15, wherein a difference between the first phase and the second different phase is ninety degrees.

17. The magnetic field sensor of claim 15, wherein the generating the AC magnetic field comprises:

generating current signal;

modulating the current signal to generate a modulated current signal having the first frequency; and

coupling the modulated current signal to at least one coil disposed proximate to the at least one magnetic field sensing element, the at least one coil configured to generate the AC reference magnetic field.

18. The method of claim 15, further comprising:

generating a reference field signal responsive to the AC reference magnetic field and not responsive to the external magnetic field, wherein the generating the reference field signal comprises modulating the modulated combined signal; and

at the same time, generating an external field signal responsive to the external magnetic field and not responsive to the AC reference magnetic field, wherein the generating the external field signal comprises modulating the modulated combined signal.

19. The method of claim 18, wherein the generating the reference field signal comprises modulating the modulated combined signal with the same first frequency, and, wherein the generating the external field signal comprises modulating the modulated combined signal with a frequency different than the first frequency.

20. The method of claim 18, further comprising:

generating a feedback signal to control an amplitude of the external field signal according to an amplitude of the reference field signal.

21. The method of claim 18, wherein the generating the feedback signal is operable to correct error fluctuations in a transfer characteristic of the magnetic field sensor.

22. The method of claim 15, wherein the at least one magnetic field sensing element comprises first and second magnetic field sensing elements coupled so as to constructively combine output signals therefrom.

23. The method of claim 15, wherein the at least one magnetic field sensing element comprises first and second Hall elements coupled so as to constructively combine output signals therefrom, wherein the first and second Hall elements are driven in respective coupling arrangements representative of current spinning phases that are ninety degrees apart.

24. The method of claim 15, wherein the at least one magnetic field sensing element comprises first and second Hall elements coupled so as to constructively combine output signals therefrom, wherein the first and second Hall elements are driven in respective coupling arrangements representative of current spinning phases that are the same.

25. The method of claim 15, wherein the at least one magnetic field sensing element comprises at least one Hall element, wherein the method further comprises:

current spinning by redirecting drive currents to, and redirecting output connections to, different nodes of the at least one Hall element at a spinning rate having a spinning frequency.

26. The method of claim 25, wherein the at least one magnetic field sensing element comprises first and second Hall elements coupled so as to constructively combine output signals therefrom, wherein the first and second Hall elements are driven in respective coupling arrangements representative of current spinning phases that are ninety degrees apart.