A 0.5-$\mu$V$_{\rm rms}$ 12-$\mu$W Wirelessly Powered Patch-Type Healthcare Sensor for Wearable Body Sensor Network

Abstract

A wirelessly powered patch-type healthcare sensor IC is presented for a wearable body sensor network (W-BSN) to continuously monitor personal vital signals. Thick-film electrodes are screen printed on a fabric by planar-fashionable circuit board (P-FCB) technology on which stainless steel powder with a grain size of 100 μ m is added to reduce both contact impedance as well as motion artifacts. A nested chopped amplifier (NCA) is designed and optimized for the proposed patch-type healthcare sensor with a reduced electrode referred noise of 0.5 μVrms. A programmable gain and bandwidth amplifier (PGA) stage is also implemented to accommodate various dynamic ranges of vital signals. A 10-b folded successive approximation register (SAR) analog-to-digital converter (ADC) reduces capacitive digital-to-analog conversion size by 94% and relaxes the power budget of the ADC driver by 36%. Measured sensor resolution is 9.2 b and rejects common-mode interference larger than 100 dB while consuming only 12 μ W of power supplied wirelessly. A 2.0 mm × 1.3 mm sensor IC is fabricated in 0.18-μm 1P6M CMOS technology. The chip is directly integrated between two screen printed electrodes and stacked by a screen printed fabric inductor. With the proposed patch-type sensor, personal healthcare without expensive batteries is possible in W-BSN and greatly improves wearability and convenience in use.