A Fixed-Window Level-crossing ADC with a Single Comparator

Abstract

A fixed-window level-crossing analog-to-digital converter (LC-ADC) with a single comparator is proposed for the biomedical field. In this paper, a signal varying direction detection circuit is proposed to judge the trend of the input signal, instead of the low-precision comparator in the modified LC-ADC. The proposed LC-ADC utilizes only one continuous-time comparator instead of multiple comparators in traditional LC-ADC, leading to simplified implementation and significantly reducing the power consumption. The post-layout simulation results show that the power consumption of the proposed new signal varying direction detection circuit is significantly reduced, accounting for only 25.6% of the high-precision continuous-time comparator. Designed with a 0.18 μm CMOS technology, the core area of this LC-ADC is 0.007 mm2. With a 1.8 V supply and 1 kHz input signal frequency, it achieves 73.1-dB SNDR by consuming 20.1 μW power. The figure-of-merit value is 19.3 mm2·fJ/Conversion.