A bio-impedance readout IC with frequency sweeping from 1k-to-1MHz for electrical impedance tomography

Abstract

This paper presents a bio-impedance (BIOZ) readout IC for electrical impedance tomography (EIT). The IC includes a complete readout channel for impedance characterization at various frequencies ranging from 1k-to-1MHz, an input multiplexer and a programmable digital controller enabling multi-frequency impedance scanning from multiple locations. To relax the bandwidth requirements of the readout channel, pre-demodulation before the IA is employed. A fast channel settling mechanism (<1ms) allows quick switching between frequencies enabling a fast imaging speed. Dynamic element matching (DEM) in the current generation and chopping in the readout front-end are adopted to mitigate 1/f noise resulting in a noise floor of 38.4mQRMS. This IC, fabricated in 0.18μm, consumes 18.7 μW and 63 μW in the readout front-end and the current generator (CG), respectively. By means of in-vitro and in-vivo testing its effectivity for EIT is demonstrated.