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US 8,299,783 B2Granted
Circuits and methods for calibration of a motion detector
AssigneeAllegro MicroSystems, LLC
InventorsDevon Fernandez, Glenn A. Forrest
Life of this patent
Estimating the term…
Abstract
A circuit to detect a movement of an object has a calibration time period that ends when peak detectors in the circuit stop updating for a predetermined amount of time. A method associated with the circuit is also described.
Claims25
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.
3 more elements
A method, used in a magnetic field sensor, of detecting a movement of an object, comprising:
- generating a DIFF signal with at least one magnetic field sensing element, wherein the DIFF signal is proportional to a magnetic field associated with the object;
- generating a tracking signal to track the DIFF signal, wherein the generating the tracking signal comprises:
- generating a positive digital-to-analog converter (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 magnetic field sensor is calibrated, and wherein the update time interval is a time interval within the calibration time period during which the PDAC is updated;
- generating a negative digital-to-analog converter (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
- establishing an end of the calibration time period, wherein the establishing comprises:
- determining if a first time period since an end of the PDAC update time interval is greater than a first predetermined time threshold;
- and
- determining if a second time period since an end of the NDAC update time interval is greater than a second predetermined time threshold.
6 more elements
A method, used in a magnetic field sensor, of detecting movement of an object, comprising:
- generating a magnetic field signal with at least one magnetic field sensing element, wherein the magnetic field signal is proportional to a magnetic field associated with the object;
- generating a tracking signal during a calibration mode of operation that moves toward a peak of the magnetic field signal at least until the peak is reached, wherein the calibration mode occurs during a calibration time period during which at least one as aspect of the magnetic field sensor is calibrated;
- and
- terminating the calibration mode of operation after a predetermined time interval has lapsed since the tracking signal reached the peak of the magnetic field signal.
1 more element
Dependencies are inferred from the claim text.