Patent ID: 8299783

Claim:
A circuit for detecting a movement of an object, comprising: at least one magnetic field sensing element for generating a DIFF signal proportional to a magnetic field associated with the object; at least one motion detector coupled to receive the DIFF signal and configured to generate a tracking signal to track the DIFF signal so as to move toward a peak of the DIFF signal, wherein the at least one motion detector comprises: a positive digital-to-analog converter (PDAC) configured to generate a PDAC output signal to track the DIFF signal during a PDAC update time interval within a calibration time period and to hold the DIFF signal at times outside of the PDAC update time interval within the calibration time period, wherein the calibration time period is a time period during which at least one aspect of the circuit is calibrated, and wherein the PDAC update time interval is a time interval within the calibration time period during which the PDAC is updated; a negative digital-to-analog converter (NDAC) configured to generate an NDAC output signal to track the DIFF signal during an NDAC update time interval within the calibration time period and to hold the DIFF signal at times outside of the NDAC update time interval within the calibration time period, wherein the NDAC update time interval is a time interval within the calibration time period during which the NDAC is updated; and an update logic circuit coupled to the PDAC and to the NDAC, wherein the update logic circuit is configured to establish an end of the calibration time period by determining if a first time period since an end of the PDAC update time interval is greater than a first predetermined time threshold and by determining if a second time period since an end of the NDAC update time interval is greater than a second predetermined time threshold.