6-bit 1-GS/s Partially Active Flash ADC with Comparator Offset Correction

This paper presents a low-power 6-bit 1 GS/s partially active flash analog-to-digital converters (ADC) in 65-nm CMOS technology. A novel comparator offset correction technique is proposed, which does not require additional foreground calibration cycles. The partially active second-stage comparison is employed for power efficiency. A third-stage comparison is introduced for offset correction using fifteen low-offset comparators, out of which two are activated. The 0.5-bit redundancy from the first-stage provides the tolerance to track-and-hold (T/H) buffer settling error for high-speed applications. The simulation results show that the ADC achieves a signal-to-noise and distortion ratio (SNDR) of 36.36 dB and a spurious-free dynamic range (SFDR) of 48.65 dB at a Nyquist frequency of 500 MHz with the power consumption of 13.98 mW.