Integrated Fluxgate Magnetometer for Use in Isolated Current Sensing

This paper presents two integrated magnetic sensor ICs for isolated current measurement that have a fluxgate magnetometer co-integrated along with circuitry on a die. The integrated fluxgate has a sensitivity of 250 V/T and a 500 ksps readout circuit and requires only 5.4 mW for fluxgate excitation, which is 20x more power-efficient than the state of the art. The fluxgate magnetometer was used to realize the first fully integrated sensor IC for closed-loop current sensing. It achieves a dynamic range of 112 dB and a nonlinearity below 0.03%. A second realization provides a precision magnetic sensor IC that can be used for open-loop and differential-field current sensing. It features a sensor gain variation of 0.04% (1-sigma), a nonlinearity below 0.2%, a bandwidth of 47 kHz, and a dynamic range of 100 dB.