A 1.55 μW Bio-Impedance Measurement System for Implantable Cardiac Pacemakers in 0.18 μm CMOS

This paper presents an implantable bio-impedance measurement system for cardiac pacemakers. The fully integrated system features a low power analog front-end and pulse width modulated output. The bio-impedance readout benefits from voltage to time conversion to achieve a very low power consumption for wirelessly transmitting the data outside the body. The proposed IC is fabricated in a 0.18 μm CMOS process and is capable of measuring the bio-impedance at 2 kHz over a wide dynamic range from 100 Ω to 3.3 kΩ with 1.35 Ω
_rms
accuracy and 1 μA maximum current injection while consuming just 1.55 μA from a 1 V supply.