A High Resolution Interface for Kelvin

Abstract

Impedance sensing, together with impedance spec- troscopy is a powerful tool detecting charge and mass transfe r phenomena at complex interfaces between materials. It is widely used in electrochemical interfaces characterization and biosensing techniques. Recently, it has been proposed as a reli able readout technique to probe biomolecular interactions on modi fied elec- trodes in enzyme biosensors, DNA biosensors and immunosensors. Unfortunately, the requirements of impedance ch aracterization accuracy, precision and dynamic range demanded by some specific application is usually accompli shed by using cumbersome labora- tory instrumentation. In this paper we present a fully integrated standalone, high precision, low power, 4-core impedance sensing interface to be implemented in the fast-growing application field of the ubiquitous sensing. The interfac e is based on a fully digital approach based on a ΔΣ demodulation that is able to achieve 15 bit of resolution, 150 ppm of temperature accuracy and dynamic ranges varying from 86 dB to 95 dB accor ding to the impedance configuration. The 4-core chip has been implemented in 0.35 µm CMOS technology and occupies an area of 9 mm .