A Z-Axis MEMS Accelerometer with Input-Insensitive Constant Stiffness

This paper reports on a Z-axis MEMS accelerometer with see-saw structure and electrostatically tunable effective stiffness. A control approach based on PWM is proposed for the multiplexed gap-variable capacitors to retain the reduced effective stiffness by electrostatic softening when an external acceleration is applied to the MEMS accelerometer. When the effective stiffness is reduced by a factor of over 100, the proposed MEMS accelerometer realizes an Allan bias instability of 16.7 μg and a noise floor of 9 μg/Hz.