A 5-GS/s 10-b 76-mW Time-Interleaved SAR ADC in 28 nm CMOS

Abstract

This paper presents a 5-GS/s 12-way 10-b time-interleaved successive approximation register (SAR) ADC for direct sampling receivers. Proper signal and clock distribution along the multiple channels are utilized to mitigate interchannel bandwidth and timing mismatches. A digitally assisted calibration is introduced to remove the interchannel offset, gain, and timing mismatch. The T-type bootstrapped sampling switches minimize the interchannel crosstalk among top-plate sampling SAR channels and the signal-dependent leakage current during SAR conversion cycles. The power efficiency of this ADC is significantly improved by many design techniques. The merged capacitor switching algorithm leads to high switching efficiency and a smaller area. The modified reference voltage scheme optimizes input common-mode voltage of the comparators. The optimal subradix-2 capacitive DAC results in low-power reference buffers and higher conversion speed. This ADC achieves 49-dB SNR, 52-dB THD, and 42-dB SNDR up to Nyquist frequency at 5 GS/s, consumes 76 mW from 1 V supply, and occupies 0.57 mm $^{{ {2}}}$ in 28 nm CMOS technology. The implemented architecture also demonstrates high scalability to advanced CMOS technology nodes and has even higher power efficiency potential.