Allegro Microsystems, LLC

Daniel S Dwyer

Christine M Graham

P Karl Scheller

Ravi Vig

Sandra R Pinelle

Terry R Clapp

Gregory R Bowman

Glenn A Forrest

Eric G Shoemaker

Eric Burdette

Mark J Donovan

James M Bailey

Jeff Eagen

Karl P Scheller

A method of performing a self-test associated with a magnetic field sensor includes generating a proximity signal responsive to a proximity of a sensed object with one or more magnetic field sensing elements, and identifying one or more characteristic values associated with the proximity signal while the proximity signal is responding to the proximity signal, The method also includes categorizing the one or more characteristic values into three or more potential categories, including three or more categories, wherein the plurality of potential categories is representative of a plurality of discrete self-test states of the proximity signal that could occur while the proximity signal is responding to the proximity of the sensed object. The method also includes communicating at least one of the plurality of potential categories into which at least one of the one or more characteristic values was categorized. A magnetic field senor implements the above method.

Magnetic field sensors and related techniques that can communicate at least one of three or more potential categories in which one or more characteristic values of a proximity signal responsive to a proximity of a sensed object are categorized

Magnetic field sensors and related techniques can identify passing conditions, failing conditions, and marginal conditions of a sensed object. A magnetic field sensor used in the techniques can have a substrate and can have one or more magnetic field sensing elements disposed on the substrate that are configured to generate a proximity signal responsive to a proximity of the sensed object. The magnetic field sensor can have a self-test module disposed on the substrate, coupled to receive the proximity signal, configured to sample the proximity signal, by analog sampling or digitally converting, to generate a plurality of analog samples or a plurality of digital samples, respectively, each digital sample comprising a plurality of digital bits, configured to select samples from among the plurality of analog or digital samples, and configured to communicate the selected samples to outside of the magnetic field sensor.

Magnetic field sensors and related techniques provide a self-test by communicating selected analog or digital samples of a proximity signal

Magnetic field sensor and related techniques can identify passing conditions, failing conditions, and marginal conditions of a sensed object. The magnetic field sensor and techniques can use one or more peak values of a proximity signal representative of proximity of the sensed object, can generate one or more difference values representative of difference between the peak values of the proximity signal and threshold values of a threshold signal proportional to the peak values, can categorize the one or more difference values into a plurality of potential categories, wherein at least one of the plurality of potential categories is representative of a respective passing self-test and wherein another at least one of the plurality of potential categories is representative of a respective marginally passing self-test, can assign category values to the plurality of potential categories, and can communicate at least one of the plurality of category values.

Magnetic field sensors and related techniques that can provide a self-test using signals and related thresholds

A circuit to detect a movement of an object includes a magnetic field sensing element for generating a magnetic field signal proportional to a magnetic field associated with the object and a motion detector to generate a motion signal indicative of the movement of the object. The motion detector includes a peak identifying circuit to provide a peak signal and a peak sample selection module that selects a sample associated with one or more prior cycles of a magnetic field signal to generate a selected peak signal. The motion detector further includes a threshold generator to generate a threshold signal as a function of the selected peak signal and a comparator to compare the threshold signal with the magnetic field signal to generate the motion signal. Peak samples from prior magnetic field signal cycles may be averaged for use to establish the threshold signal. A method associated with the circuit is also described.

Circuits and methods for generating a threshold signal used in a magnetic field sensor based on a peak signal associated with a prior cycle of a magnetic field signal

A magnet structure including a magnet and an integral magnetically permeable concentrator and methods for making the same are provided. The concentrator is comprised of a plastic loaded with one or more magnetically permeable materials to a percentage suitable for providing desired magnetic field characteristics. The magnetic element may be comprised of a conventional magnetic material or a plastic loaded with one or more magnetic materials. An insert molding technique is described in which either the concentrator or magnetic element is prefabricated and inserted into a mold which is subsequently filled with a loaded plastic to provide the other component of the magnet structure. In an alternate fabrication technique, both the concentrator and magnet are sequentially formed by injection molding in the same mold. Also described is a magnet structure including a ring magnet having a central aperture in which a steel rod is disposed.

Method for fabricating a magnet structure

A magnet structure including a magnet and an integral magnetically permeable concentrator and methods for making the same are provided. In one embodiment, the concentrator has a substantially planar base and a post extending normal to the base and the magnetic element is a ring magnet having a central aperture through which the concentrator post extends. The concentrator is comprised of a plastic loaded with one or more magnetically permeable materials to a percentage suitable for providing desired magnetic field characteristics. The magnetic element may be comprised of a conventional magnetic material or a plastic loaded with one or more magnetic materials. An insert molding technique is described in which either the concentrator or magnetic element is prefabricated and inserted into a mold which is subsequently filled with a loaded plastic to provide the other component of the magnet structure. In an alternate fabrication technique, both the concentrator and magnet are sequentially formed by injection molding in the same mold. Also described is a magnet structure including a ring magnet having a central aperture in which a steel rod is disposed.

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Auburn, NH, United States of America

Daniel S Dwyer