Design Of Readout Circuit For MEMS Accelerometer

MEMS(Microelectromechanical Systems)accelerometers are of great significance among various accelerometers.They are applying to a wide range of motivation detection,including biomedical applications,automotive safety and stability,computer accessories and oil,gas exploration,etc.Among various mechanisms in seismic exploration,MEMS detector is the dominant sensing methods,since it not only provides excellent resolution,but also has advantages of wide dynamic range and high sensitivity.MEMS detector consists of a capacitive acceleration sensor and an application specific integrated chip(ASIC).MEMS acceleration sensor signal processing circuit is mainly used to detect the acceleration of the sensitive mass of the MEMS capacitive acceleration sensor and convert it into voltage signal.In this paper,the working principle of MEMS accelerometer readout circuit is analyzed,including MEMS sensor,capacitance detection and the readout circuit.In order to reduce the noise and improve the linearity,it adopts analog closed-loop switched capacitor detection system.The readout circuit is composed of a capacitance compensation array,a reference source,a multi-phase clock,a fully differential switched capacitor circuit,a RC low-pass filter and an instrument amplifier.The fully differential switch capacitor circuit adopts correlated double sampling technique to eliminate the imbalance,and the three op amp instrumentation amplifier structure can achieve single output from double end signal.High trigger voltage and low holding voltage are challenge of high voltage ESD(Electrostatic Discharge)in field exploration.In the readout circuit,I/O port ESD protection achieved by using complementary gate-coupling technique of PMOS and NMOS,and power clamp is gate-coupling technique NMOS,effectively improving ESD protection level.It's verified that the whole chip obtains high linearity and low noise and offset.Finally,it carried out in MXIC L50 W 0.5 ?m process.