A Single-Ended SAR ADC With Fully Differential DAC Switching Scheme for IoT Applications

This brief introduces a single-ended SAR ADC with a novel fully differential DAC switching scheme. This scheme achieves fully differential switching by smartly sampling the single-ended input and pre-switching before the conversion phase, maintaining a constant DAC output common-mode voltage during conversion. As a result, it eliminates the impact of comparator dynamic offset voltage on SAR ADC precision. Additionally, this switching scheme does not require additional reference voltages like Vcm, which reduces system complexity and peripheral circuit power consumption. The prototype is fabricated using a 110 nm CMOS process and tested with a 1 V supply voltage and 200 kHz sampling rate. The measured ENOB is 10.1 bits with a near Nyquist input frequency, resulting in a Walden figure-of-merit (FoM) of 31 fJ/conversion step.