Low-noise, low-power and extended bandwidth MEMS magnetic field sensing system

This paper shows, for the first time, a complete magnetic field sensing system including a Lorentz-force sensor operating at a frequency slightly lower than the mechanical resonance coupled to an integrated circuit for sensing and driving the device. Working out of resonance, the trade-off between maximum sensing bandwidth and minimum detectable magnetic field is overwhelmed, allowing to improve the resolution and to enlarge the bandwidth. However, the decreased signal amplitude in off-resonance operation mode makes the read-out electronics the most critical block Measurement results carried-out on the system prototype show an achievable resolution of 220 nT ·mA/ √ Hz over a larger than 100-Hz bandwidth. The integrated read-out circuit low-noise performance does not impair the resolution, limited by the MEMS thermo-mechanical noise. Dissipating less than 500 μW, the magnetic field sensing system satisfies the consumer electronics low-power requirements. Key–Words: Microelectromechanical Systems (MEMS), magnetometer, integrated circuit (IC), low-power lownoise electronics