A Sub-400-nT/ $\sqrt {\text {Hz}}$ , 775- $\mu \text{W}$ , Multi-Loop MEMS Magnetometer With Integrated Readout Electronics

This paper presents a novel z-axis Lorentz force magnetometer coupled with a low-power readout integrated circuit. The sensor is fabricated using an industrial process, and exploits an Al-on-polysilicon multi-loop architecture that gives a five-fold sensitivity and resolution improvement, useful for off-resonance operation. The integrated readout is based on a differential charge amplifier front-end, and designed to be balanced with the sensor in terms of noise and power consumption. The overall system, including demodulation and filtering stages, shows a programmable full-scale up to ±2.4 mT, limited by the electronics saturation. The bandwidth can be programmed up to 150 Hz for off-resonance operation where a sub-400-nT/√Hz resolution at 775-μW power consumption is obtained, including the integrated readout and the Lorentz current. Perspectives on low-consumption driving oscillators for off-resonance mode are finally given.