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 <inline-formula><tex-math notation="LaTeX">${\text{100}}\,\Omega $</tex-math> </inline-formula> to <inline-formula><tex-math notation="LaTeX">$\text{3.3}{\;\text{k}\Omega }$</tex-math> </inline-formula> with <inline-formula><tex-math notation="LaTeX">$\text{1.35}\;\Omega _{{\rm{rms}}}$</tex-math> </inline-formula> accuracy and <inline-formula><tex-math notation="LaTeX">${\text{1}}\; {\mu}\text{A}$</tex-math> </inline-formula> maximum current injection while consuming just <inline-formula><tex-math notation="LaTeX"> $\text{1.55}{\;{\mu}}{\text{A}}$</tex-math></inline-formula> from a 1 V supply.