| As an important inertial sensor, micro-accelerometer has broad application in field such as inertial guidance, automotive and consumer electronics. In this dissertation, we analyzed the mechanical structure of capacitive closed-loop micro-accelerometer, the principle of signal detection and closed-loop operation. Schematic of the ASIC based on continuous-time feedback for closed-loop micro-accelerometer has been designed with 0.5μm CMOS technology.The interface circuit based on continuous-time feedback for closed-loop micro-accelerometer is composed of three parts: signal detection and operation circuit, feedback control circuit and waveform generation circuit. The signal detection and operation circuit consists of charge-sensitive amplifier, high-pass filter, chopped wave demodulator, low-pass filter and instrument amplifier, and it can detect, amply and output the acceleration. PID controller can control the amplitude and phase of the feedback signal to performance system feed-back control, that conduce to improve stability and dynamic characteristic of the system. Waveform generation circuit is used to generate the high-frequency carrier and the clock used for demodulation, it also can delay the clock to set the delay between the signal and the clock to zero.Based on the ideal dynamics equation and the accelerometer structure parameters, the equivalent electrical model of the closed-loop accelerometer was established. The whole system composed of the equivalent electrical model and interface circuit was simulated with HSPICE. The circuit performance as follow: the full measurement range can be achieved±2g, the sensitivity of the system is 0.94V/g, minimum detectable acceleration is 10μg.Based on the design of the real circuit, we established equivalent noise model for the whole system. The analysis on important noise sources was presented, and arrived at some conclusions to optimize the noise characteristic of the whole system.
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