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An 8 b 700 MS/s 1 b/cycle asynchronous successive approximation register (SAR) analog to digital converter (ADC) which skips comparator metastability is presented. A delay-shift technique is proposed to shift the delay of comparator to generate a 1.5 b redundancy range and to accelerate comparison speed. This reduces the settling requirement and compensates for the dynamic offset by redundancy. The prototype ADC in 40 nm CMOS technology achieves an SNDR of 43.9 dB at Nyquist rate and consumes 5 mW with a 1.2 V supply. This results in an FoM of 56 fJ/conversion-step. Due to no extra calibration circuit, the core circuit occupies an area of only 0.006 mm 2 .

A 6-bit 1.25GS/s single-channel asynchronous SAR ADC skipping the comparator metastability is presented. A delay-shift technique is proposed to shift the comparator delay to generate the 1.5-bit redundancy range and to accelerate the comparison speed. It compensates the dynamic offset by the redundancy. This ADC in 40nm CMOS technology achieves 37.1dB peak SNDR and consumes 5.3mW at 1.2V supply. It results in an FoM of 73fJ/conversion-step. Due to no extra calibration circuit, the core circuit only occupies an area of 0.004mm 2 .Index Terms -Analog to digital converter (ADC), metastability, redundancy, successive approximation register (SAR).