16.4 A Calibration-Free 71.7dB SNDR 100MS/s 0.7mW Weighted-Averaging Correlated Level Shifting Pipelined SAR ADC with Speed-Enhancement Scheme

With the increasing demand for next-generation communication, the trend of developing wide-bandwidth, high-resolution ADCs has emerged, where pipelined SAR (PIPE-SAR) ADCs [1], [2] have become popular owing to their excellent power-efficiency due to the fewer number of opamps. However, the finite opamp gain error limits the resolution of PIPE-SAR ADCs. Without calibration, this work proposes the weighted-averaging correlated level shifting (WACLS) technique for PIPE-SAR ADCs to theoretically eliminate the finite opamp gain error and operate with a speed-enhancement scheme to overcome the speed-degradation drawback of the prior two-phase CLS-based residue amplification [3], [4]. In addition, a duty-cycle-controlled ring amplifier (ringamp) with quick start-up is proposed for power saving.