A Novel Time-Multiplexed Fully Differential Interface ASIC With Strong Nonlinear Suppression for MEMS Accelerometers

In this article, a novel time-multiplexed fully differential (TMFD) interface ASIC with strong nonlinear suppression is presented. The interface ASIC adopts the half-bridge measurement method and two single-end charge amplifiers in the novel $C$ – $V$ converter instead of the conventional full-bridge sensing structure. The $C$ – $V$ converter can greatly suppress the influence of the common-mode voltage by declining the gain of virtual ground node for charge transfer. As a result, the nonlinearity of the front-end circuit decreases obviously due to the low common-mode disturbance. This article also proposes a TMFD switched-capacitor (SC) programmable gain amplifier (PGA) with continuous output to suppress the fluctuation caused by discrete signals from conventional SC PGA. The readout circuit chip was implemented in a 1P3M 0.18- $\mu \text{m}$ CMOS process. The operating frequency reaches 200 kHz with a power consumption of 2.5 mA from a 3.3-V power supply. Due to the strong nonlinear suppression capability of the proposed interface ASIC, the measuring sensitivity of the accelerometer achieved 0.530 V/g with only a dc-nonlinearity of 0.08%. The experimental results at different operating temperatures indicate that the presented readout ASIC performs great temperature stability. The temperature sensitivity ratio reduces to 0.008% ‰/K. The experimental results indicate that the nonlinearity has reduced significantly compared with conventional readout chips.