An asynchronous 8x interleaved redundant SAR ADC achieving 8.8GS/s at 35mW and 1V supply is presented. The ADC features pass-gate clocking for time-skew minimization and per-channel gain control based on low-power reference voltage buffers. The sub-ADC stacks the capacitive SAR DAC (CDAC) with the reference capacitor to reduce the area and enhance the settling speed. It achieves 38.5dB SNDR and 58fJ/conversion-step with a core chip area of 0.025mm2 in 32nm CMOS SOI technology.