A Bio-Impedance Measurement IC for Neural Interface Applications

Employing a bio-impedance monitoring system can significantly improve the measurement quality of biomedical signals by investigating the working condition of electrodes and estimating the effects of the spurious signals, caused by motion artifact, cellular damage, or electrode degradation. Accordingly, a biomedical system that acquires weak biomedical signals can be reconfigured or even excluded according to the bio-impedance measured by adjusting the gain of low noise amplifiers deployed in the system. In this paper, we propose a bio-impedance measurement IC, which can be adopted for neural recording and stimulation systems, capable of measuring both real and imaginary parts of the tissue impedance. The proposed system is capable of measuring bio-impedance ranging from 1 kΩ to 100 kΩ with a 68-Ω resolution, while consuming only 55 μW from a 1.8 V supply. The chip has been designed in TSMC 0.35-μm standard CMOS process and occupies 0.055 mm
²
excluding pads.