A 100-to-10-kHz 5.4-to-216-μW Power-Efficient Readout Circuit Employing Closed-Loop Dynamic Amplifier for MEMS Capacitive Accelerometer

Micro-electromechanical systems (MEMS) capacitive accelerometer for the Internet of Things (IoT) applications is required to operate at various sampling frequencies while keeping high power efficiency. To meet this requirement, dynamic amplifiers are used in the readout circuit of the accelerometer. However, the dynamic amplifier's open-loop gain is low and varies with the sampling frequency of the readout circuit. This significantly deteriorates the gain accuracy of the readout circuit. In this article, the dynamic-amplifier-specific oversampling successive approximation (DA-OSA) readout technique is proposed to overcome this gain variation problem and make the dynamic amplifier applicable to the readout circuit. The DA-OSA-based readout circuit is fabricated in a commercial 0.18-mu m 1.8-V CMOS process and tested with the MEMS accelerometer sensing element. The measurement results show that, with the sampling frequency varying from 10 kHz to 1 MHz, the proposed readout circuit achieves a variable signal bandwidth from 100 Hz to 10 kHz, a variable power consumption from 5.4 to 216 mu W, and a low gain variation of 1.2%.

Automated summary

This article proposes a dynamic-amplifier-specific oversampling successive approximation (DA-OSA) readout technique to overcome gain variation problems in MEMS capacitive accelerometers for IoT applications. Experimental results show that the proposed readout circuit achieves variable signal bandwidth (100 Hz to 10 kHz), power consumption (5.4 to 216 mu W), and low gain variation (1.2%) for sampling frequencies ranging from 10 kHz to 1 MHz.