Design of magnetic sensing microsystem with hall sensors

Magnetic sensors are transducers which convert magnetic field into electrical signals. A class of magnetic sensors is Hall Effect sensor where transportation of the electrons in the electrical device is affected by the presence of the external magnetic field to produce a voltage difference with a magnitude depending on the external magnetic field, Hall Voltage. Hall Effect 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 flexibility. They are widely used in various industrial and automotive applications. This dissertation presents development of a compact cross-shaped Hall Effect sensor model and design of readout electronics for the magnetic sensing microsystem with Hall Effect sensor using UMC 130 nm CMOS technology. The presented technology allows sensing magnetic field with a low offset and low noise microsystem. The Hall Effect sensor is biased by a biasing circuit which implements dynamic offset cancellation method for cancelling sensor offsets due to fabrication imperfections and mechanical stress; and, Hall Voltage is amplified by an amplifier with a chopper technique realization for improving resolution of the microsystem and rejecting amplifier offset and low-frequency noise of the microsystem. The simulation results present a residual offset due to sensor offsets of 40 uV, corresponding to an input-inferred residual offset of 7.62 uT; and an input-inferred offset of 1.62 uV for a standard offset of 1 mV at amplifier input. Moreover, RMS noise voltage of 167 uV in the bandwidth of 1 Hz – 1 kHz at the microsystem output enables a microsystem resolution as low as 31.75 uT. Finally, the absolute sensitivity of the microsystem is 5.25 V/T.