一种用于电容型体硅微陀螺的低噪声读出电路芯片

A Low-Noise Readout Circuit for Bulk Micro-Machined Capacitive Gyroscope

读出电路位于微传感器系统信号通路的最前端,是决定系统性能的关键因素。本文针对音叉式体硅微陀螺的具体应用,提出了一种低噪声电容读出电路,芯片采用斩波技术降低了电路的低频1/f噪声、失调电压以及参考电压失配的影响,提高了读出电路的分辨率和动态范围;提出一种噪声电荷转移的分析方法,用于分析和预测读出电路的噪声性能;建立一种简化的微陀螺传感器仿真模型,用于模拟读出电路对微传感器的响应。读出电路在0.35μm 2P4 M标准CMOS工艺下设计流片,并与微传感器进行了联合应用,芯片面积为2×2.5mm2,在5V电源电压,100kHz的时钟频率下,实现了4aF/Hz的电容分辨率和94dB的动态范围。

Readout circuit is a key factor determining the performance of MEMS gyroscope system, being at the forefront of the signal loop. This paper presents a low-noise readout circuit for a bulk micromachined tuning fork gyroscope. Using the chopper technique, the circuit can improve the resolution and dynamic range by canceling 1/f noise and offset of the amplifier, and mismatch between reference voltages. Theory predicting the resolution of the readout circuit is given which is based on noise charge transfer method. In order to simulate the response of the circuit with the vibrating gyroscope, a simplified time-varying capacitor model is also proposed. The chip measures 2×2.5mm^2 in a standard 0.35 μm 2P4M CMOS process. Chip tests with the MEMS gyroscope prove the validity of the concepts proposed and show that the readout circuit achieves a resolution of 4aF/√Hz with 94 dB dynamic range from a single 5 V supply.