MEMS陀螺仪高精度低噪声检测电路设计

Design of high-precision and low-noise detection circuit for MEMS gyroscope

为满足电容式MEMS陀螺仪低噪声,高精度的检测需求,设计了一款基于开关电容结构的全差分检测电路,主要包括电容检测和数字量化处理两部分。电容检测电路采用离散时间电容电压(C/V)转换方案,提出将高频载波调制和相关双采样技术相结合的方式,有效降低了低频噪声的干扰。量化电路采用一款4阶4 bit单环前馈结构的带通ΔΣ调制器,输入信号前馈通路的引入提高了系统的稳定性,内部多位量化器有效提高了信噪比。系统在保持低功耗的同时实现了高精度输出。基于0.18μm BCD工艺,在5 V电源电压下,对整体电路进行仿真验证。仿真结果表明,检测电路灵敏度可以实现10 m V/f F,在谐振频率5 k Hz处,等效输入电容噪声为■。最终在100 Hz带宽范围内,读出信号量化精度可以达到15 bits。与传统的MEMS陀螺仪检测电路相比,该电路具有更低的噪声和更高的量化精度,能够满足高精度检测应用需求。

To fulfill the demands of achieving low-noise and high-precision detection of capacitive MEMS gyroscopes,this paper presents a fully differential sensing circuit based on a switched capacitor structure.The design consists of two parts:capacitance detection and digital quantization processing.The discrete-time capacitor to voltage (C/V) conversion scheme is used for capacitance detection.The method of combining high frequency carrier modulation and correlated double sampling technique is proposed to reduce the low frequency noise.The quantization circuit adopts a bandpassΔΣmodulator with a 4th-order,4-bit single-loop feedforward structure.The input signal feedforward pathway is introduced to improve the stability of the system.The internal multi-bit quantizer is used to improve the signal-to-noise ratio.The system achieves high precision with low power consumption.Based on the 0.18μm BCD process,the overall circuit is simulated and verified under a 5 V power supply.The simulation results demonstrate that the sensitivity of the detection circuit can reach 10 m V/f F,and the equivalent input capacitive noise is ■ at 5 kHz.The quantization accuracy of the readout signal can be up to 15 bits in the bandwidth range of 100 Hz.Compared with the traditional MEMS gyroscope sensing circuit,this circuit has lower noise and higher quantization accuracy.It is suitable for high-precision detection.