A Real-Time Rotation Calibration for Interchannel Offset Mismatch in Time-Interleaved SAR ADCs

Abstract

This brief presents an on-chip, real-time rotation calibration (RRC) technique aimed at alleviating the inter-channel offset mismatch in time-interleaved (TI) successive-approximation register analog-to-digital converter (SAR ADC). By leveraging auto-rotation calibration and self-compensation strategies in the analog domain, the proposed technique demonstrates robust performance across PVT variations. Two additional sub-channels are involved in the TI quantization mechanism, where the continuous rotation of the sampling clock distribution ensures their operation in calibration mode. To validate the effectiveness of the proposed calibration, an $8\times 8$ bit 8 GS/s TI-SAR ADC is designed and implemented in a 28-nm process and occupies an active area of 0.273 mm2, with each sub-channel SAR ADC covering only $86\times 23~\mu $ m. Extensive simulation results validate the efficacy of RRC, demonstrating significant improvements in dynamic performance. Specifically, SNDR increases from 37.1 to 45.4 dB, while SFDR rises from 57.8 to 60.7 dB, as observed at the Nyquist input frequency.