A Low-power Level-Crossing ADC for Biosignal Acquisition

Abstract

A large number of redundant signals will be generated when the traditional Nyquist sampling method is used to acquire a biological signal, leading to a system’s energy loss. A new level-crossing analog-to-digital converter (LC-ADC) with non-uniform sampling and fixed window structure is presented, with fewer data and low power consumption features. The circuit uses a 6-bit capacitive DAC to quantize the input signal, avoiding the error accumulation of the 1-bit capacitive DAC structure, and a nanoamp CMOS current bias circuit to provide a very low quiescent current for the comparator, further reducing power consumption. The structure was verified in a 0.18μm CMOS technology. The results indicate that the total power dissipation is 0.26uw@500Hz, the signal-to-noise distortion ratio (SNDR) is 59dB@500Hz, and ENOB reached 9.51bit, which is suitable for the acquisition of low-frequency biological signals.