5th order sigma delta MEMS accelerometer system with enhanced linearity

Aykutlu, Ulaş
This thesis reports the linearity enhanced 5th order sigma delta MEMS accelerometer readout circuit utilizing varying gap type capacitive MEMS accelerometer sensor. While varying gap type capacitive MEMS accelerometers provide high sensitivity, high reliability and high shock tolerance suitable for navigation grade applications, these types of mechanical sensors suffer from the non-linear input to output relation even in the closed loop operation due to the limited loop gain. Thus, this research aims to improve the linearity performance and eliminate the non-linear behavior of mechanical sensor by employing PI controller in the sigma delta interface circuit designed previously in METU-MEMS Center. In order to achieve this goal, firstly the non linear behavior of the capacitive MEMS accelerometer is examined. Then, MATLAB-Simulink simulations are performed to demonstrate the enhancement in the linearity performance of the accelerometer system taking advantage of PI controller in the loop. Programmable PI controller which enables integration of various MEMS accelerometer with the readout circuit is implemented carefully using XFab 0.35µm CMOS process to guarantee low noise and bias instability while providing enhanced linearity performance. Designed readout is integrated with the MEMS accelerometer which is fabricated at METU-MEMS Center in a 16-pin metal package to perform system level performance tests.
Citation Formats
U. Aykutlu, “5th order sigma delta MEMS accelerometer system with enhanced linearity,” M.S. - Master of Science, Middle East Technical University, 2015.