Circuits and methods for self-calibrating or self-testing a magnetic field sensor using phase discrimination
First Claim
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1. A magnetic field sensor, comprising:
- a reference magnetic field generator, wherein the reference magnetic field generator is configured to generate an alternating current (AC) signal having a first frequency with a first phase and to generate an alternating current (AC) reference magnetic field having the same first frequency with the same 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 alternating current (AC) reference magnetic field and also responsive to an external magnetic field at the same time, wherein the combined signal comprises, at the same time, an alternating current (AC) reference magnetic field signal component and an external magnetic field signal component, and wherein the at least one magnetic field sensing element is responsive to the alternating current (AC) reference magnetic field and, at the same time, is also responsive to the 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 a modulation signal having the same first frequency as the alternating current (AC) signal but with a second phase different than the first phase of the alternating current (AC) signal to generate a modulated combined signal.
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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.
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Citations
34 Claims
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1. A magnetic field sensor, comprising:
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a reference magnetic field generator, wherein the reference magnetic field generator is configured to generate an alternating current (AC) signal having a first frequency with a first phase and to generate an alternating current (AC) reference magnetic field having the same first frequency with the same 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 alternating current (AC) reference magnetic field and also responsive to an external magnetic field at the same time, wherein the combined signal comprises, at the same time, an alternating current (AC) reference magnetic field signal component and an external magnetic field signal component, and wherein the at least one magnetic field sensing element is responsive to the alternating current (AC) reference magnetic field and, at the same time, is also responsive to the 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 a modulation signal having the same first frequency as the alternating current (AC) signal but with a second phase different than the first phase of the alternating current (AC) signal to generate a modulated combined signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 27, 28, 29, 30)
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15. A method used on a magnetic field sensor, the method comprising:
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generating an alternating current (AC) signal field having a first frequency with a first phase to generate a reference magnetic field having the same first frequency with the same first phase; generating, with at least one magnetic field sensing element, a combined output signal responsive to the alternating current (AC) reference magnetic field and also responsive to an external magnetic field at the same time, wherein the combined signal comprises, at the same time, an alternating current (AC) reference magnetic field signal component and an external magnetic field signal component, and wherein the at least one magnetic field sensing element is responsive to the alternating current (AC) reference magnetic field and, at the same time, is also responsive to the external magnetic field; and modulating the combined signal with a modulation signal having the same first frequency as the alternating current (AC) signal but with a second phase different than the first phase of the alternating current (AC) signal to generate a modulated combined signal. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 31, 32, 33, 34)
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Specification