Auto-calibrating a magnetic field sensor

Abstract

In one embodiment a method to compensate for the sensitivity drift of a magnetic field sensor for sensing a magnetic field comprises forming a reference magnetic field having first magnetic field parameters, e.g. a first amplitude and/or direction, in a first step and second magnetic field parameters, a second amplitude and/or direction, in a second step and a bias signal is formed without adjusting the bias signal with a feedback signal derived from an output signal of the magnetic field sensor.

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         13 . A method to compensate the sensitivity drift of a magnetic field sensor for sensing a magnetic field, the sensor comprising at least four electrodes, the method comprising:
 a first step where a first set of two electrodes is used to bias the sensor and a second set of two electrodes is used to sense an output signal of the magnetic field sensor; and   a second step where the second set of two electrodes is used to bias the sensor and the first set of two electrodes is used to sense an output signal of the magnetic field sensor;   the method being characterized in that:   a reference magnetic field is formed having first magnetic field parameters in the first step and second magnetic field parameters in the second step; and   the output signal is sensed in the first and in the second steps wherein during both the first and second steps the bias signal is formed without adjusting the bias signal with a feedback signal that is derived from the output signal.   
     
     
         14 . A method according to  claim 13 , characterized in that the second step includes first and second sub-steps and wherein during both the first step and one of the first and second sub-steps of the second step the reference magnetic field has a first amplitude and a first phase that are substantially equal and during only one of the first or second sub-steps the reference magnetic field has one of a) an amplitude that is different than the first magnetic field parameters, b) a zero amplitude, or c) the first amplitude and an opposite phase to the first phase. 
     
     
         15 . A method according to claim.  13 , characterized in that the second step includes first and second sub-steps and wherein during both the first step and one of the first and second sub-steps of the second step the reference magnetic field has a first amplitude and a first phase that are substantially equal and during only one of the first or second sub-steps the reference magnetic field has one of a) a greater amplitude than the first amplitude and has the first phase, or b) a zero amplitude.