A 0.02mm2 100dB-DR Impedance Monitoring IC with PWM-Dual GRO Architecture

This paper presents an impedance monitoring IC that achieves small area and wide DR. The stimulated signal is encoded by using pulse width modulation (PWM) and complex impedance can be measured by in- (I) and quadrature- (Q) phase outputs through dual phase demodulation. The two-level I/Q signals drive two gated-ring-oscillator (GRO) based ADCs, thus eliminating the distortion of GROs. Fabricated in 0.11μm CMOS, the prototype IC occupies only 0.02mm
²
. It achieves a wide DR of 100dB and a resolution of 19.21Ω
_rms
at 1MΩ resistance in a conversion time of 5ms, and consumes 152.3μW. It corresponds to state-of-the-art resolution FoM of 14.6pJ/step.