Study On The Monolithic Interface Circuit For MEMS Capacitive Accelerometer

Capacitive MEMS accelerometer has the advantage of high resolution, large dynamic range and low temperature drift and is widely used in the areas like inertia navigation, micro gravity test and the oil prospect which have more resolution requirements. Using bulk micromachining and silicon bonding we can achieve high-performance full-silicon sandwich accelerometer. But the interface circuit of capacitive transducers is complex and sensitive to the stray capacitance on the board. With the development of the CMOS technology, the integrated detecting technology has been the trend. The integrated MEMS capacitive accelerometer interface circuit will be studied here in this dissertation.First, a new Verilog-A simulation model for sandwich capacitive accelerometers is proposed which is based on the sensor's dynamic equation and differential capacitor structure. Stray capacitances and thermo-mechanical noise are taken account into the model. It has portability and compatibility with the modern IC design environments. So it is possible to simulate the senor together with the interface circuit. From the simulation results of the model, step response, frequency response, noise characteristic is analyzed.Then, we choose the switched capacitor interface circuit considering of the advantage of insensitivity of the stray capacitance. The whole capacitive transducer interface is designed and optimized through the analysis and comparison of different approaches of function models. The noise and non-ideality is considered and simulated to achieve the design specific. Finally, by simulating the transducer and interface circuit together, we get the different step and transient responses. The comparison of simulation results of the correlated double sampling scheme shows it decreases the noise and low frequency offset.