A 1.4-m $\Omega$ -Sensitivity 94-dB Dynamic-Range Electrical Impedance Tomography SoC and 48-Channel Hub-SoC for 3-D Lung Ventilation Monitoring System

Abstract

A wearable electrical impedance tomography (EIT) system is proposed for the portable real-time 3-D lung ventilation monitoring. It consists of two types of SoCs, active electrode (AE)-SoC and Hub-SoC, mounted on wearable belts. The 48-channel AE-SoCs are integrated on flexible printed circuit board belt, and Hub-SoC is integrated in the hub module which performs data gathering and wireless communication between an external imaging device. To get high accuracy under the variation of conductivity, the dual-mode current stimulator provides the optimal frequency for time difference-EIT and frequency difference-EIT with simultaneous 4 k–128 kHz impedance sensing. A wide dynamic range instruments amplifier is proposed to provide 94 dB of wide dynamic range impedance sensing. In addition, the 48-channel AE system with the dedicated communication and calibration is implemented to achieve 1.4- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega $ </tex-math></inline-formula> sensitivity of impedance difference in the in vivo environment. The AE-/Hub-SoCs occupy 3.2 and 1.3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in 65-nm CMOS technology and consume <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$124~\mu \text{W}$ </tex-math></inline-formula> and 1.1 mW with 1.2 V supply, respectively. As a result, EIT images are reconstructed with 90% of accuracy, and up to 10 frames/s real-time 3-D lung images are successfully displayed.