Integrated micro search coil magnetic sensor

Abstract

A fully integrated micro search coil magnetometer (µSCM) with a low-noise instrumentation amplifier is provided for low-frequency magnetic field measurements in the range of 1Hz to 1kHz. A micro search coil formed by stacking planar spiral inductors and serially connecting them with an in-phase configuration is used for magnetic field measurements. The critical line width and inner diameter of a planar spiral inductor are theoretically calculated and experimentally verified, enabling the development of a unique CMOS layout. This layout incorporates the calculated critical inner diameter, significantly optimizing the area utilization on the CMOS die. Additionally, the CMOS die includes a polysilicon-layer inductor for on-chip calibration, a Hall effect sensor for DC magnetic field measurement, and a temperature sensor for enhanced functionality. The µSCM delivers a compact, energy-efficient, and highly sensitive solution for low-frequency magnetic field measurements, surpassing the performance of most commercially available Hall effect sensors.