A 6 bit 2 GS/s flash-assisted time-interleaved (FATI) SAR ADC with background offset calibration

A power-efficient and speed-enhancing technique for time-interleaved (TI) SAR ADCs that is assisted by a low-resolution flash ADC is presented. The 3 b MSBs achieved from a flash ADC at every clock save two decision cycles from every SAR ADC channel, resulting in a reduced number of time interleaving channels with a total 27% energy saving compared with the energy consumption of a conventional TI SAR ADC. A prototype 6 b 2 GS/s ADC in a 45 nm CMOS consumes 14.4 mW under a 1.2 V supply and achieves 5.2 ENOB_Nyq with a background offset calibration.