A Research On Interface Circuits Of Closed-Acceleromenter

Based on analyzing the principle of the closed-loop accelerometer and combining the experience of the open-loop accelerometer designed by HIT MEMS center, the interface circuits of the closed-loop accelerometer is designed by using the process parameter of CSMC 0.5μm DPDM.The circuits composed of two parts. They are analog part and digital part. The analog part includes the switch controlling circuits, driving circuits, operation amplifier, sample/hold circuits, phase modulating circuits, unity gain buffer, current reference source, compensation capacity array, voltage conversion circuit. Compensation capacity array in the absence of acceleration-sensitive condition also verify the whole circuits function. The digital part includes closed loop oscillator, frequency divider, combinational logic circuit, non-overlapping clock generation circuit. By using the digital part, the entire circuit get 8 different phase sequence controlling signal. Each signal don't occur the overlapping clock. The accelerometer system is placed in several states by digital circuits which control the opening and closing of various switches. The digital circuits operate at a clock frequency of 2MHz. A repetitive cycle includes 32 states. Each cycle includes three phases: Sensing phase, sample phase, and forcing phase. Each cycle starts with the end of the forcing period and beginning of sensing phase. The circuits performance as follow: the full measurement range can be achieved from -3g to +3g, the sensitivity of the system is 0.78V/g, the minimum acceleration detected can be achieved 30μg.And the compensation capacity array could to a certain extent prevent capacity deviation.The thesis has completed the layout of the whole circuit, by LPE extracting parameter to verify the function of the circuits.