0.0354mm 82μW 125KS/s 3-axis readout circuit for capacitive MEMS accelerometer

Abstract

In this paper, we propose a power/area-efficient capacitive readout circuit for the Micro-Electro-Mechanical Systems (MEMS) sensor of 3-axis accelerometer. The proposed architecture is different from other traditional structures by exploiting true capacitive-to-digital converter (CDC) without Analog-to-Digital Converter (ADC). The proposed CDC can differentiate the bidirectional 125KS/s 80-level accelerations between 8g and support the 4-level adjustable resolutions of 0.1g/ 0.2g/ 0.4g/ 0.8g for each axis. The proposed readout circuit with 0.0354mm 2 area is fabricated in UMC 0.18um CMOS-MEMS process. Experimental results show power consumption is 50uW with 1.8V supply voltage for 1-axis (FOM=3.84pJ), 82uW for 3-axis (FOM=2.1pJ) under 125KHz of sampling frequency and 0.1g acceleration sensitivity for 0.2fF MEMS capacitance change.

A 3.3V 15.6b 6.1pJ/0.02%RH with 10ms response humidity sensor for respiratory monitoring

“…Recently, some digital output readout circuits have been presented to improve the power consumption and energy efficiency for the sensing applications [2][3][4]. To further achieve better power efficiency and sensitivity, an eventdriven approach with high sensitivity readout circuits has been proposed in [5,6], where power is consumed only when significant capacitance change appears. Accordingly, an event-driven and ultrafast response humidity sensor is proposed in this paper to work with cardiac sensor electrocardiography (ECG), chest cavity downs and respiration for cross reference.…”