Patent ID: 8736260
Filing Date: 2014-05-27
Classification: G01D,G01P

Abstract:
1. A magnetic field sensor, comprising: a magnetic field sensing element responsive to a changing magnetic field and configured to generate a magnetic field signal having an amplitude; an amplitude module configured to generate an amplitude signal representative of the amplitude of the magnetic field signal; a measured threshold module coupled to receive a positive peak signal and a negative peak signal representative of positive peaks and negative peaks, respectively, of the magnetic field signal, and configured to generate a measured threshold signal in accordance with the positive peak signal and the negative peak signal; a temperature sensor configured to sense a temperature of the magnetic field sensor and configured to generate a temperature signal in accordance with the temperature; a temperature coefficient module coupled to receive the temperature signal, coupled to receive the amplitude signal, and configured to generate a temperature coefficient signal in accordance with the temperature signal and the amplitude signal; a memory device coupled to receive and configured to store, at each one of a plurality of storage times, a respective value of the temperature coefficient signal and a respective value of the measured threshold signal; a threshold module coupled to receive, at a calculation time, a stored value of the temperature coefficient signal and a stored value of the measured threshold signal, each stored at a selected one of the plurality of storage times prior to the calculation time, coupled to receive the temperature signal, and configured to combine the received stored value of the temperature coefficient signal, the received stored value of the measured threshold signal, and the temperature signal to generate a calculated threshold value; and a true power on state (TPOS) detector coupled to receive the calculated threshold value and also coupled to receive a signal representative of the magnetic field signal, wherein the true power on state (TPOS) detector is configured to compare the calculated threshold value with a signal representative of the magnetic field signal to generate an output signal.