Circuits and methods for generating a threshold signal used in a motion detector in accordance with a least common multiple of a set of possible quantities of features upon a target

摘要

A circuit to detect a movement of an object provides a threshold selection module or a peak identifier module that uses one or more threshold signals identified prior to a present cycle of magnetic field signal in order to establish a threshold signal used for a present cycle of the magnetic field signal. A method associated with the circuit is also described. The circuit and method can be tailored to store values associated with a least common multiple of a set of possible quantities of detectable features on target objects.

主权项

1. A magnetic field sensor for detecting a movement of an object, wherein the object has a plurality of object features, wherein a quantity of the object features belongs to a set of possible quantities of object features, wherein the set has a least common multiple of possible quantities of object features, wherein the magnetic field sensor comprises:
a magnetic field sensing element for generating a magnetic field signal responsive to the object features as they pass by the magnetic field sensing element, wherein the magnetic field signal comprises a plurality of magnetic field signal cycles, wherein each one of the plurality of magnetic field signal cycles is indicative of a respective one of the plurality of object features passing by the magnetic field sensing element, wherein the plurality of magnetic field signal cycles includes a present magnetic field signal cycle and a plurality of past magnetic field signal cycles; and a motion detector coupled to the magnetic field sensing element and configured to generate a motion signal indicative of the movement of the object, wherein the motion signal has a plurality of rising edges and a plurality of falling edges, wherein each rising edge and each falling edge is associated with a respective one of the plurality of magnetic field signal cycles, wherein the motion detector comprises:
a peak identifying circuit for identifying at least one of a plurality of positive peaks of the magnetic field signal or a plurality of negative peaks of the magnetic field signal to provide a peak signal indicative of the at least one of the plurality of positive peaks of the magnetic field signal or of the plurality of negative peak of the magnetic field signal;a sample selection circuit module coupled to receive a peak-related signal related to the peak signal and configured to store a plurality of samples of the peak-related signal, wherein the sample selection circuit module is further configured to sequentially recall stored samples of the peak-related signal from the stored plurality of samples to generate a sampled signal, wherein each sequentially selected stored sample within the sampled signal is associated with a respective one of the plurality of prior cycles of the magnetic field signal that occurred a quantity of prior cycles ago equal to an integer multiple of the least common multiple of the possible quantities of the object features; anda comparator coupled to receive a signal related to the sampled signal, coupled to receive the magnetic field signal, and configured to compare the signal related to the sampled signal with the magnetic field signal in order to generate the motion signal.