A Low-Power Fully Differential Level-Crossing ADC Based on Single-Reference Comparator for Wireless Medical Implantable Devices

Abstract

This paper introduces a low-power fully differential fixed window level-crossing analog-to-digital converter (LC-ADC) for wireless medical implantable devices. The LC-ADC could be an excellent candidate for low-power systems due to the reduction of sampling points for bio-potential signals. Different from existing fixed window LC-ADCs, which use a 1-bit DAC or scaler and two reference levels to move the input signal to the comparison window, a simplified scheme is proposed in which the DAC or scaler is removed and a single-reference level is used to create the comparison window. The proposed LC-ADC utilizes a single-reference comparator, which leads to a simplified implementation and significant reduction in power consumption and circuit area. In addition, using a single reference level and removing DAC, leads to a decrease in the complexity of the controlling logic. The proposed LC-ADC is simulated in 0.18 [Formula: see text]m CMOS technology. The simulation results achieve an effective number of bits (ENOB) of up to 6.5 bits with about 59–141 nW power consumption under 0.8 V supply and input signal bandwidth from 5 Hz to 4 kHz.