Fault detection scheme for a variable reluctance sensor interface having

Abstract

In accordance with the teachings of the present invention, a fault detection circuit is provided which detects short circuits on differential leads associated with a magnetic sensor and modifies said differential voltage to avoid possible errors associated with a short circuit. The circuit includes a first and second input coupled to first and second signal lines for receiving a differential voltage. A first voltage comparator compares voltage potentials at the first and second signal lines so as to detect equal voltage crossings and provide an output in response thereto. A rectifier is coupled to the first and second signal lines in the output of the first comparator and has first and second outputs for producing positive half-wave voltage cycles with a voltage potential at each of the first and second lead lines. A second comparator is provided for comparing the half-wave voltage cycles with a first threshold voltage that represents a short circuit power source. A third comparator is provided for comparing the half-wave voltage cycles with a second threshold voltage that represents a short circuit to ground. The voltage potentials at the first and second signal lines are converted to separate single-ended voltages when one of the second and third voltage comparators detects a short circuit so as to correct for possible errors caused by the short circuit.