Study of a three-axis digital tunneling resistance-type magnetic sensor

Abstract

In this paper, an interface circuit for a three-axis digital tunneling resistance-type magnetic sensor in a standard 0.5 µm CMOS technology is presented. The weak signal detection is achieved by the chopper instrumentation amplifier. The conversion between analog and digital is achieved by the fully differential fourth-order forward Sigma-Delta modulator. The output zero-bias of magnetic sensor is corrected by digital auto-offset circuit. The design and fabrication of tunneling resistance-type magnetic sensor interface ASIC with digital output have been achieved by the research. The performance of magnetic sensor is shown as below: the sensor is at 5 V operating voltage, the value of consumption is only 120 mW; the nonlinear of the sensor is 0.1%FS; the zero reference output is less than 10 nT; the equivalent input noise density is less than 0.13 nT/Hz^1/2 (at 10 Hz).