A 2D CMOS microfluxgate sensor system for digital detection of weak magnetic fields

This paper presents a CMOS two-dimensional (2-D) vector magnetic sensor system integrating two planar microfluxgate sensors and the complete electronics for sensor excitation and signal readout. The system is based on an industrial 0.8-/spl mu/m double-poly, double-metal CMOS technology with ferromagnetic NiFeMo cores added in a simple postprocessing sequence. The fluxgate sensors are embedded in a /spl Sigma//spl Delta/ analog-to-digital converter for a stable and precise digital detection of weak magnetic fields. A cascaded /spl Sigma//spl Delta/ modulator topology is utilized to obtain second-order noise shaping and to suppress pattern noise. Within the range of /spl plusmn/50 /spl mu/T, the system nonlinearity is less than 1.5 /spl mu/T. The angular resolution as a 2D vector sensor is less than 4/spl deg/ for a measured magnetic induction of 50 /spl mu/T. This makes the 2-D microfluxgate magnetometer suitable for use as fully integrated electronic compass.