Systems and Methods for Magnetic Field Sensors with Self-Test

摘要

Systems, methods, and apparatuses for magnetic field sensors with self-test include a detection circuit to detect speed and direction of a target. One or more circuits to test accuracy of the detected speed and direction may be included. One or more circuits to test accuracy of an oscillator may also be included. One or more circuits to test the accuracy of an analog-to-digital converter may also be included. Additionally, one or more IDDQ and/or built-in-self test (BIST) circuits may be included.

主权项

1. An apparatus comprising:
a detection circuit to detect speed and direction of a target, the detection circuit comprising:
one or more magnetic field sensing elements;a first signal channel to output a first signal;a second signal channel to output a second signal, wherein the first and second signals correspond to a position of the target in relation to the one or more magnetic field sensing elements;an oscillator to provide an oscillating output; andan analog-to-digital converter; a first test circuit to determine if the apparatus is detecting speed and/or direction accurately, the first test circuit comprising a counter coupled to the signal channels such that the first signal channel increments the counter and the second signal channels decrements the counter, the first test circuit including circuitry to assert an error condition if a count of the counter exceeds a predetermined threshold; a second test circuit coupled to the oscillator to determine whether the oscillator is oscillating within a predetermined frequency range, the second test circuit comprising a ramp generator to generate a voltage ramp signal that decays over time and resets upon detection of an edge of the oscillating output, and a comparator circuit to determine whether a voltage level of the voltage ramp signal is between a predetermined voltage range upon detection of the edge of the oscillating output; a third test circuit coupled to the analog-to-digital converter to determine whether the analog-to-digital converter is operating with an expected accuracy, the third test circuit comprising an output to inject an analog test signal into an input of the analog-to-digital converter, an input coupled to receive a digital signal from the analog-to-digital converter representing a conversion of the analog test signal; and a comparator circuit to compare the digital signal to an expected value; and a fourth test circuit coupled to receive the digital signal from the analog-to-digital converter, compute a rate of change of the output of the analog-to-digital converter, and determine whether the rate of change is within a predetermined range defined by a mechanical system to which the target is attached.