Design of a CMOS MEMS Accelerometer Used in IoT Devices for Seismic Detection

Abstract

This paper reports a design for a complementary metal oxide semiconductor (CMOS) microelectromechanical system accelerometer used in Internet of Things (IoT) devices for seismic detection. The proposed device performs the main functions of accelerometers, and has the advantage of automatically selecting the electrostatic force of feedback to null the position of the sensor. This paper applied $0.35~\mu \text{m}$ 2P4M CMOS technology with a 3-V power supply. The sensitivity of the continuous time voltage analog sensing circuits was 131.99 mV/g and the maximal nonlinearity was 1.21% over the excitation of 0.25 to 6.75 g (1 g = 9.8 m/s2) intensity. The noise floor was 0.579 mg/Hz1/2. The cross-axis Y and cross-axis Z nonlinearity were less than 0.05% and 1.38%, respectively. Under an excitation of 2.75 g intensity, the peak signal-to-noise-plus-distortion ratio (SNDR) of the proposed accelerometer was 72 dB, and decreased to 49.1 dB after 3 weeks of continuous shaking. After enabling automatically nulling of the sensor for 0.5 s period of time, the peak SNDR was 75.2 dB. Based on this operational mode, the nulling accelerometer could be applied for usage in IoT devices for seismic detection. The measurement results verify the functions and performance of the proposed accelerometer. Experimental monitoring of river bridge vibration was also successfully conducted.