Design of magnetic sensing microsystem with hall sensors

Abstract

Magnetic sensors are transducers which convert magnetic eld into electrical signals. A class of magnetic sensors is Hall E ect sensor where transportation of the electrons in the electrical device is a ected by the presence of the external magnetic eld to produce a voltage di erence with a magnitude depending on the external magnetic eld, Hall Voltage. Hall E ect sensors, formed by Hall element and signal-conditioning electronics integrated on the same integrated circuit fabricated in CMOS technology, include the advantages of small size, high speed, low cost, long life, and design exibility. They are widely used in various industrial and automotive applications. This dissertation presents development of a compact cross-shaped Hall E ect sensor model and design of readout electronics for the magnetic sensing microsystem with Hall E ect sensor using UMC 130 nm CMOS technology. The presented technology allows sensing magnetic eld with a low o set and low noise microsystem. The Hall E ect sensor is biased by a biasing circuit which implements dynamic o set cancellation method for cancelling sensor o sets due to fabrication imperfections and mechanical stress; and, Hall Voltage is ampli ed by an ampli er with a chopper technique realization for improving resolution of the microsystem and rejecting ampli er o set and low-frequency noise of the microsystem. The simulation results present a residual o set due to sensor o sets of 40 V, corresponding to an input-inferred residual o set of 7.62 T; and an input-inferred o set of 1.62 V for a standard o set of 1 mV at ampli er input. Moreover, RMS noise voltage of 167 V in the bandwidth of 1 Hz { 1 kHz at the microsystem output enables a microsystem resolution as low as 31.75 T. Finally, the absolute sensitivity of the microsystem is 5.25 V/T.