A 4.5fJ/conversion-step 9-bit 35MS/s configurable-gain SAR ADC in a compact area

Good energy efficiency and area efficiency are both achieved for the presented 9-bit 35MS/s SAR ADC, by using customized small-value capacitors in a splitting monotonic switching scheme, a simplified dynamic digital logic and a self-clocked dynamic comparator. With built-in configurable gain, the ADC maintains its peak SNDR over a wide input range, featuring more flexibility. Fabricated in a 65nm CMOS technology, the ADC consumes 46.1μW at 35MS/s from 1V supply voltage, and achieves an SNDR of 51dB and an ENOB of 8.18bits at Nyquist rate, resulting in a figure of merit (FoM) of 4.5fJ/conversion-step. The core circuit only occupies 0.009mm², which is very compact.