A 25-µW All-MOS Potentiostatic Delta-Sigma ADC for Smart Electrochemical Sensors

This paper presents a low-power all-MOS delta-sigma ADC specifically optimized for the potentiostatic biasing and amperometric read-out of electrochemical sensors. The proposed architecture reuses the dynamic properties of the sensor itself to implement a continuous-time mixed electrochemical delta-sigma modulator with minimalist analog circuits fully integrable in purely digital CMOS technologies. A 25-µW smart electrochemical sensor demonstrator integrated in low-cost 1M CMOS technology with Au post-processing is presented. Experimental results show electrical dynamic range values exceeding 10-bit, while electrochemical figures exhibit linearity levels close to R² = 0.999 combined with RSD < 15% in terms of reproducibility. A comparative test with commercial potentiostat equipment is also included to qualify the performance of the proposed ADC.