Ternary-level thermometer C-DAC switching scheme for flash-assisted SAR ADCs

Abstract

A ternary-level thermometer capacitive digital-to-analog converter (C-DAC) switching scheme is proposed for flash-assisted successive-approximation register (FA-SAR) analog-to-digital converters (ADCs). By minimizing the capacitor reference switching operations of the C-DAC with the help of thermometer codes readily available from the assistant flash ADC, integral nonlinearity (INL) and differential nonlinearity (DNL), as well as C-DAC switching energy, are significantly improved from conventional switching schemes, which in turn makes near thermal-noise-limited capacitor designs feasible without complex capacitor weight calibrations.