A 4.5-mW 8-b 750-MS/s 2-b/step asynchronous subranged SAR ADC in 28-nm CMOS technology

Abstract

A 8-b 2-b/step asynchronous subranged SAR ADC is presented. It incorporates subranging technique to obtain fast reference settling for MSB conversion. The capacitive interpolation reduces number of NMOS switches and lowers matching requirement of a resistive DAC. The proposed timing scheme avoids the need of specific duty cycle of external clock for defining sampling period in a conventional asynchronous SAR ADC. Operating at 750 MS/s, this ADC consumes 4.5 mW from 1-V supply, achieves ENOB of 7.2 and FOM of 41 fJ/conversion-step. It is fabricated in 28-nm CMOS technology and occupies an active area of 0.004 mm2.