Dual-channel pulse-width-modulation ASIC for isolated bio-signal recording front-end

This paper presents a pulse-width-modulation (PWM) analog-to-digital converter for the transmission of signals across an all-digital isolation barrier of a bio-signal recording front-end. The system provides two ground-referenced channels and digital logic to generate a pseudodifferential as well as a common-mode output. Measured results of a prototype integrated circuit in TSMC 0.35 μm CMOS technology are reported. The PWM circuit consumes 36 μW from 3 V supplies including bias circuitry and the active area for two channels is <;0.46 mm². SINAD and ENOB measured at the 8-bit receiving end are 46 dB and 7.5 bit respectively, suitable for the transmission of bio-signals as demonstrated with the electrocardiogram (ECG).