Integrated ExG, Vibration and Temperature Measurement Front-End for Wearable Sensing

This paper presents a programmable CMOS integrated front-end ASIC targeting the acquisition of signals in biomedical applications, including rehabilitation and treadmill exercise monitoring. The analog front-end is combined with a commercial microcontroller for clock generation, signal processing, and feedback generation. The ASIC provides a unique combination of sensing interfaces, including a dc-coupled ExG monitor including variable gain amplification with 34–60 dB tunable gain range, 31-step offset compensation, as well as a capacitive sensor readout for piezoelectric vibration measurement (which can alternatively be used as a buffer for sensors with voltage output) providing 28.6-dB attenuation and <tex-math notation="LaTeX">16~Vₚₚ </tex-math> effective input range below 100 Hz, a 1 °C-precision thermometer, a 50-/60-Hz switched-capacitor notch filter for mains interference reduction, and an 8-bit analog-to-digital pulse-width-modulating converter. The design is realized in 180-nm technology where it occupies an area of 0.06 mm 2 . Measured results are reported which confirm the intended operation.