A CMOS front-end circuit for integrated fluxgate magnetic sensors

In this paper an integrated CMOS front-end circuit for a micro-integrated fluxgate magnetometer is proposed. The system is based on excitation block, that feeds the excitation coil of the sensor and a read-out block that sense the voltage of the pick-up coils. To sense the output signal, the second harmonic detection principle has been chosen to achieve a good compromise between power consumption and noise requirements. An integrated low pass Sallen-Key filter has been used to extract the dc signal after the demodulation. The preliminary measurements, performed with a PCB sensor, show a sensitivity of 920 V/T and a linearity error of 6% full scale. The circuit has been realized in a standard 0.35 mum CMOS process. The power consumption is 8 mW @ 3.3V for the excitation and read-out parts and unit and 42 mW @ 5V for the output power stage