A Low Noise Readout Circuit With Input-Common-Mode-Feedback Charge Sensitive Amplifier Using Differential Pseudo Resistors for MEMS Gyroscopes
Wenbo Zhang, Xin Yu, Yihang Wang, Xiaokun Zhan, Huan Zhang, Xinpeng Di, Liang Yin, Haifeng Zhang, Qiang Fu, Liang Yin, Xiangyu Li
Abstract
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-order <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Sigma \Delta $</tex-math> </inline-formula> modulator in the readout circuit. The readout circuit is fabricated using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18\mu $</tex-math> </inline-formula>m BCD process and achieves bias instability (BI) and angle random walk (ARW) of 0.11°/h and 0.035°/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd $</tex-math> </inline-formula>Hz, respectively combined with MEMS gyroscope and digital circuits. The CSA achieves a capacitance resolution, power consumption, and area consumption of 7.56zF/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd $</tex-math> </inline-formula>Hz, 1.28mW, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$48720\mu $</tex-math> </inline-formula>m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, respectively.