State-Space Control of Force-Feedback MEMS Accelerometers with 115-dB Dynamic Range

The research proposes the use of state-space feedback control for closed-loop MEMS capacitive accelerometers targeting low noise and wide full-scale range (FSR). The state-space feedback control is implemented in the digital domain, allowing noise reduction and high flexibility in the sizing of the loop gain and bandwidth. The analog portion of the system is limited to the sense front-end amplifier and the force-to-rebalance drivers. The state-space feedback is realized using a linear-quadratic regulator (LQR). Behavioral simulations show that a FSR as high as ±100 g with an input referred noise equal to 4 μg/√Hz (limited by the thermo-mechanical noise) can be achieved. Experimental measurements result in 12 μg/√Hz and 80-g measured full scale (sub-0.1% linearity error) with programmable bandwidth in the few hundreds Hz range.