Design Of Closed Loop Driving Circuits For MEMS Silicon Gyroscope Based On PLL

The prodigious value of Silicon MEMS gyroscope has spread out in military, aerospace industry and civil fields. In the recent years, as the grown of the MEMS technology, MEMS gyroscope has become the hot research point. MEMS gyroscope consist of sensor and interface circuit, the whole performance of MEMS gyroscope depends much on the interface circuit. A closed loop drive circuit based on phase locking loop theory is proposed in the thesis, the closed loop self-excitation drive circuit is realized for the MEMS gyroscope, and the performance of the interface circuit is analyzed.Firstly, the thesis introduces the operating principle of MEMS gyroscope with electrostatic driving and capacitive sensing, and based on the kinetics model of the MEMS gyroscope sensor, the equivalent circuit model is presented, and the parameters of the equivalent circuit model are deduced. The result of the simulation for the equivalent circuit model show that the drive sense current is maximal as the drive voltage frequency and gyroscope sensor inherent resonance frequency are equally.As is known drive sense current keep the same phase and frequency with drive voltage while MEMS gyroscope sensor resonates in the drive axis, and the phase locking loop circuit could lock the phase and frequency accurately, so the closed loop drive circuit combine with phase locking loop circuit could realize a stable resonance, stable frequency is gyroscope sensor inherent resonance frequency. The main design work contain closed loop drive circuit model building and simulation in Matlab, MOS transistor realize and simulation in Cadence, layout and post simulation. Then do some analysis work like loop stability, resonance building time, frequency stability, etc.The main circuit modules contain C-V convert circuit, phase shift circuit, amplifier, phase locking circuit, proportion circuit. Drive sense current convert to voltage signal, the phase shift circuit compensates the voltage signal’s phase offset, the phase locking circuit lock the frequency, then provide the drive voltage. Due to the same frequency drive voltage, the drive loop resonant quickly, the result of simulation show that the frequency error less than 0.2Hz after 150 ms, and the drive loop resonance frequency is 2.7739 k Hz.