An integrated micro fluxgate magnetic sensor

This paper presents an integrated micro fluxgate magnetic sensor with planar fluxgate sensing elements and on-chip sensor interface circuits based on silicon integration technology. To simplify the integration process, we developed a noble sensing element with two-layer spiral coils and permalloy thin films at the top layer. The sensor interface circuits have been fabricated with the standard n-channel E/D (enhancement/depletion) MOS process technology, and include the driver circuits for the periodic excitation of the core through the excitation coil and signal-processing circuits for the pick-up coil output based on second-harmonic detection. The fabricated planar sensing element has a magnetic sensitivity of about 73 V T(-)1 at 1 MHz excitation frequency and 150 mA(p-p) driver current. The magnetic sensitivity of the integrated fluxgate sensor is about 90 V T-1 at 610 kHz excitation frequency and 110 mA(p-p) driver current.