An area-efficient wideband CMOS hall sensor system for camera autofocus systems

Abstract

This paper presents an area-efficient and fast-response CMOS Hall sensor system for a camera autofocus system. The prototype comprises of a Hall sensor and a capacitively-coupled instrumentation amplifier (CCIA). The Hall sensor adopts the spinning current technique to mitigate the Hall element offset. In the CCIA, the T-capacitor network is employed considering the capacitor matching requirement and the chip area. The amplifier offset is further suppressed by a ripple-reduction loop. This chip is measured with Helmholtz coil, Solenoid, and NMR system. Implemented in a 0.18-μm CMOS process, it achieves 564 μT rms in 180-kHz BW. The linearity error is < 0.5% over ±100-mT range. The power consumption is 1.19 mW, and the area is 0.12 mm2.