A 12b 180MS/s 0.068mm2 With Full-Calibration-Integrated Pipelined-SAR ADC

This paper presents a 12b 180 MS/s 0.068 mm
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2× time-interleaved pipelined-SAR analog-to-digital converter (ADC) with gain and offset calibrations fully embedded on-chip. The proposed binary-search gain calibration (BSGC) technique corrects the inter-stage gain error caused by the open-loop residue amplifier. The BSGC, fully integrated into the second-stage SAR ADC, contributes to a compact area. We improve the noise performance by implementing a mergedresidue-DAC operation in the first-stage ADC. Also, we propose a dual-phase bootstrap technique to improve the sampling linearity in the partial interleaving architecture. The measurement results of the ADC prototype in 65 nm CMOS demonstrate the effectiveness of the proposed calibration through the enhancement of the signal to noise-and-distortion ratio from 51.5 to 60.9 dB at a Nyquist input, leading to a FoM@Nyq of 36.7 fJ/conversion-step.