A Closed-loop CMOS Interface for ±1g MEMS Capacitive Accelerometer

This paper presents a simple CMOS interfacing circuit for a single-axis closed loop MEMS capacitive accelerometer. The designed accelerometer consists of a MEMS based acceleration sensor and an analog readout circuit with continuous time feedback. The interfacing circuit for the closed loop accelerometer is designed using SCL 180 nm CMOS process technology. A PI controller has been incorporated in the design to improve the stability of the accelerometer. To ensure the operation of the accelerometer, an equivalent model for closed loop accelerometer is implemented using Cadence Analog Design Environment and the complete system is simulated. Although the complete interface uses a 1.8V supply voltage, to provide the necessary actuation to the accelerometer, the feedback amplifier works with a 3.3V supply voltage. The change in the supply voltage enables the accelerometer to function in a closed loop and also improves the range of accelerometer. The closed-loop accelerometer is designed for an input range of ±1g.