This paper presents a wideband 12Bit 8GS/s TI SAR ADC, featuring a sub-2 radix architecture and randomized sampling with mismatch correction in a 28nm CMOS technology. For this purpose, 18 500MHz SAR-ADCs plus an additional reference ADC are interleaved. Furthermore, the additional reference ADC operating in parallel to the main ADC enables adaptive digital calibration to correct for static and time-interleaved mismatch effects. After calibration, the ADC achieves a SNDR of 56.8dB and a SFDR of 80dBc applying a single full scale sine wave tone close to the Nyquist frequency of 4GHz.