Resolution and Start-up Dynamics of MEMS Resonant Accelerometers

In this paper it is presented a study on two key parameters of MEMS resonant accelerometers, resolution and start-up dynamics. A uniaxial differential accelerometer, built in the surface micromachining ThELMA process of ST Microelectronics, is used in the tests together with a discrete components readout circuit. The implemented circuit is an oscillator constituted by a Transimpedance stage (TIA) followed by a gain stage and an amplitude-limiting circuit (ALC). In the present work, it is shown how the sensor resolution can be related to the phase noise of the oscillator output signal and how the start-up dynamics depends on the biasing voltage of the resonator. A sensing resolution of 98 mu g/root Hz is demonstrated through experimental measurements and a well-defined relationship between the resonators biasing voltage and the start-up time is observed.