高精度MEMS硅陀螺仪接口ASIC设计

Design of High-Precision MEMS Silicon Gyroscope Interface ASIC

摘要:

为满足惯性导航、自动驾驶等领域的应用需求，实现微电子机械系统（MEMS）硅陀螺仪向高精度、数字化和微小型化的方向发展，本文基于0.35 μm BCD工艺（双极型-互补金属氧化物半导体-双扩散金属氧化物半导体工艺），采用单芯片集成方式，设计并实现了一款具有数字化输出的MEMS硅陀螺仪接口电路。采用基于噪声自激的闭环驱动方案，使陀螺仪在驱动方向上实现简谐振动。检测电路使用低噪声电容-电压（C/V）转换电路，将检测模态位移信号转换为电压信号。信号处理通过开关相敏解调技术进行精确解调，并结合低通滤波处理，有效抑制系统噪声，从而获得低噪声的模拟角速度输出信号。为了实现硅陀螺角速度的数字化输出，设计了集成的四阶全前馈Sigma-Delta （ΣΔ）模数转换器（ADC），将模拟角速度信号转换为数字信号。芯片测试结果表明：ΣΔ调制器的动态范围达到110 dB，低频噪底约为-120 dB。陀螺整机的量程为±200(°)/s，标度因数为21 310 LSB/（(°)/s）（最低有效位每度每秒），非线性误差为178×10^-6，零偏不稳定性为0.259(°)/h，角度随机游走为0.028 7(°)/√h（度每平方根小时）。该芯片面积为4.3 mm×4.3 mm。通过采用单片集成的接口ASIC（专用集成电路）替代传统的PCB（印制电路板）板级系统，显著提高了系统集成度，成功满足了MEMS硅陀螺微小型化的需求，推动了其在高精度数字化应用中的发展。

Abstract:

To meet the application requirements of inertial navigation, autonomous driving, and other fields, and to advance the development of micro-electromechanical systems (MEMS) silicon gyroscopes towards high precision, digitalization, and miniaturization, this paper presents the design and implementation of a MEMS silicon gyroscope interface ASIC with digital output, based on a 0.35 μm BCD process and a monolithic integration approach. A closed-loop drive scheme based on noise self-excitation is adopted, enabling the gyroscope to achieve harmonic vibration in the drive direction. The detection circuit uses a low-noise capacitive-to-voltage (C/V) conversion circuit to efficiently convert the small displacement signal into a voltage signal. Signal processing is performed using switched-capacitor phase-sensitive demodulation technology, combined with low-pass filtering, effectively suppressing noise interference and yielding a low-noise analog angular velocity output signal. To achieve the digital output of the silicon gyroscope's angular velocity, an integrated fourth-order feed-forward Sigma-Delta (ΣΔ) analog-to-digital converter (ADC) is designed to convert the analog angular velocity signal into a digital signal. The chip test results show that the dynamic range of the ΣΔ modulator reaches 110 dB, with a low-frequency noise floor of approximately -120 dB. The overall range of the gyroscope is ±200(°)/s, with a scale factor of 21 310 LSB/((°)/s), a nonlinearity of 178×10^-6, bias instability of 0.259(°)/h, and angle random walk of 0.028 7(°)/√h. The chip area is 4.3 mm×4.3 mm. By using the integrated interface ASIC to replace the traditional PCB-level system, the system's integration is significantly improved, successfully meeting the miniaturization requirements for MEMS silicon gyroscopes and promoting their development in high-precision digital applications.