A Low Noise Readout Circuit With Input-Common-Mode-Feedback Charge Sensitive Amplifier Using Differential Pseudo Resistors for MEMS Gyroscopes

This paper aims to design a high-performance interface readout circuit for MEMS gyroscopes, focusing on the low-noise, fully integrated design of the front-end charge-sensitive amplifier (CSA) within the readout circuit. It first reveals themechanism by which the voltage-resistance characteristics of the pseudo-resistor used to improve the integration level influence the common-mode voltage, and emphasizes the necessity of stabilizing the input common-mode voltage with the continuous-time CSA in gyroscope systems. Based on this theory, a fully integrated CSA based on input common-mode feedback is proposed. TheCSAachieves comprehensive optimization of noise and power consumption by reusing the input common-mode feedback circuit and differential-mode detection circuit. Furthermore, the CSA employs a novel differential pseudo-resistor structure, which reduces the noise, area, and power consumption of this part of the circuit by reusing the pseudo-resistor bias circuits. The paper also presents the specific implementation of the PGA and 4th-orderΣ Δmodulator in the readout circuit. The readout circuit is fabricated using a0.18μm BCD process and achieves bias instability (BI) and angle random walk (ARW) of 0.11°/h and 0.035°/Hz, respectively combined with MEMS gyroscope and digital circuits. The CSA achieves a capacitance resolution, power consumption, and area consumption of 7.56zF/Hz, 1.28mW, and48720μm2, respectively.