A 21 fJ/Conversion-Step 100 kS/s 10-bit ADC With a Low-Noise Time-Domain Comparator for Low-Power Sensor Interface

Abstract

This paper presents a 100 kS/s, 1.3 mu W, 9.3 ENOB successive approximation ADC with a time-domain comparator. The proposed time-domain comparator utilizes a differential multi-stage VCDL, resulting in a highly digital operation eliminating static power consumption. The effects of gain, noise, and offset are also investigated by detailed analysis which proves the feature of reducing the input-referred noise and offset by simply increasing the number of delay stages. For verification, the proposed ADC is fabricated in a 0.18 mu m CMOS. With a single supply voltage of 0.6 V, the ADC consumes 1.3 mu W at the maximum sampling rate of 100 kS/s. The measured ENOB is 9.3 b showing a figure of merit of 21 fJ/conversion-step.