Pipelined Gray encoding scheme for ultra-high sampling rate Flash ADCs

This paper analyzes and verifies Gray encoding schemes with a proposed pipelined Gray encoding scheme for ultra-high sampling rate Flash ADCs. The Gray encoding scheme significantly suppresses the sparkles and meta-stability errors of parallelized comparators of ultra-high sampling rate Flash ADCs. 4-b Flash ADCs are implemented with different encoding schemes in the 0.13μm CMOS digital process. The results show that using the proposed pipelined Gray encoding scheme, the 4-b ADC achieves 5dB more in SNR at 4GSPS. This is about 20% improvement of SNR from using thermometer-to-1-of-n-to-binary encoding scheme.