High speed densor circuit for stabilized hall effect sensor

Abstract

An improved Hall effect sensor includes a four-terminal Hall plate with orthogonally paired terminals that produce voltage signals in response to changes in an ambient magnetic field created by the proximity of a ferrous gear tooth to the sensor. Voltage signals from orthogonally paired terminals of the Hall plate are controlled by switches that are coupled to a clock signal generator. In response to the clock signal, the switches allow current to flow in a first direction corresponding to a first phase of the clock and to flow in a second direction corresponding to a second phase of the clock. A plurality of pass gate transistors in the sensor circuitry are connected to a timing generator synchronized with the clock signal generator. The timing generator outputs are received by the gate transistors and the gate transistors control the sequence in which a plurality of capacitors are charged. This plurality of capacitors store the voltage output from the Hall plate. The capacitors are charged in pairs so that one capacitor of the pair receives a voltage signal from a first terminal pair while the other receives a voltage signal from an orthogonal terminal pair as determined by the gate transistors. There are multiple capacitors corresponding to each terminal pair on the Hall plate. Once a capacitor pair is charged, both capacitors in the pair are discharged in response to another signal from the timing generator. Furthermore, they are discharged so that only correctly paired capacitors are discharged simultaneously. Because there are multiple capacitors corresponding to each terminal pair, each of the capacitors is relatively smaller and has a faster response time. Thus, the time delay in responding to the input signal is minimized.