A 92-dB-DR 126-μν Sensitivity Potentiometrie Sensor Interface with High Interference Robustness

A fully differential Potentiometric sensor interface consisting of a high input impedance programmable-gain preamplification stage followed by a delta-sigma (ΔΣ) ADC is presented. The reconfigurable circuit achieves a dynamic range of 92 dB and a resolution of 126 μν, thus enabling electrochemical analyses for multiple biochemical parameters. The fully differential topology of the signal acquisition chain in combination with the use of feedforward compensated opamps leads to a high interference robustness of the implementation. Compared to a single-ended topology, PSRR, CMRR and EMIRR improvements by 43.3 dB, 6.8 dB and 21.6 dB, respectively, are achieved. These properties and the low power and area consumption of 75 μW and 0.081 mm² allow the circuit to be used in wirelessly powered electrochemical point-of-care (PoC) diagnostics.

I. Introduction

Electrochemical point-of-care (PoC) diagnostics have received increasing attention in medical treatment over the past decade. Wireless power transfer (WPT) has become an important factor in keeping the costs of the diagnostics at a minimum by avoiding the need for an additional energy storage device [1]. However, the wireless operation and the associated limited power and quality of the on-chip supply place high demands on the circuits that form the interface to the electrochemical sensor.