A 6.5-μW 70-dB 0.18-μm CMOS Potentiostatic Delta-Sigma for Electrochemical Sensors

Abstract

This paper presents the design of a low-power potentiostatic second-order continuous-time (CT) delta-sigma modulator $( \Delta \Sigma \mathrm {M})$ for the amperometric read-out and A/D conversion of electrochemical sensors. The proposed architecture reuses the sensor itself as a leaky integrator stage for shaping the quantization noise, resulting in a very compact and energy efficient read-out front end. Low-power CMOS circuits are also presented for the remaining analog blocks of the $\Delta \Sigma \mathrm {M}$ loop. A design example in $0 . 18-{\mu }\mathrm {m}$ CMOS technology is provided with a total area of $0 . 063$mm2. Post-layout simulations show a dynamic range of 70dB with an overall power consumption of $6 . 5{\mu }\mathrm {W}$ at $1 . 8-\mathrm {V}$ supply.