A multi-frequency bioimpedance measurement ASIC for electrical impedance tomography

This paper presents an integrated circuit for the measurement of tissue impedances. The circuit will be part of a wearable electrical impedance tomography based imaging system intended to be used for neonate lung function monitoring in intensive care units. The ASIC is designed to measure the real and imaginary parts of tissue impedances at two different frequencies simultaneously. It includes both circuitry for current injection and impedance measurement. The readout part employs synchronous chopping detection. The ASIC was fabricated in a 0.6-μm CMOS technology, occupies a core area of 4.5 mm² and dissipates about 10 mW from ±2.5 V power supplies. It has wideband frequency operation, from DC to about 1 MHz, and a measurement accuracy of less than 1 Ω.