Browsing by Author "He, Zih-Cheng"

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A 0.0354mm(2) 82 mu W 125KS/s 3-Axis Readout Circuit for Capacitive MEMS Accelerometer
(2013)
Lai, Kelvin Yi-Tse
;
He, Zih-Cheng
;
Yang, Yu-Tao
;
Chang, Hsie-Chia
;
Lee, Chen-Yi
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
(2014)
Lai, Kelvin Yi-Tse
;
Yang, Yu-Tao
;
Chen, Bang-Jing
;
Shen, Chun-Jen
;
Shiu, Ming-Feng
An event-driven and energy-efficient humidity sensor for environment detection and healthcare monitoring is presented. A differential CMOS-MEMS humidity device and proportion-based capacitance-to-digit readout circuit are proposed to overcome PVT variations, and in the meantime to improve sensitivity, response time, and conversion energy. This chip achieves 15.6b 20-90 % RH at 1KS/s, 6.1pJ per 0.02% RH of sensitivity, and 10ms fast response time in TSMC 0.35-mu m CMOS MEMS process. With variations in temperature and voltage, our proposal can minimize the errors from 40% RH to 0.2% RH and 50% RH to 0.1% RH, making it very suitable for wearable respiratory monitoring.