A 7-b 76-mW 40-GS/s Hybrid Voltage/Time-Domain ADC With Common-Mode Input Tracking

High-speed links require fast, moderate resolution analog-to-digital converters (ADCs) with low power to maximize efficiency. Hybrid voltage and time (V+T) ADCs can combine the speed benefits of time-domain conversion with the reliability of conventional voltage-domain ADCs. This letter demonstrates 1) how the V+T architecture can simplify time interleaving implementation and 2) highlights two methods for improving V+T sub-ADC robustness: a) a voltage-to-time converter (VTC) with common-mode input voltage tracking and b) a merged time-to-voltage and flash time-to-digital converter. This is demonstrated in a 0.103-mm2 22-nm CMOS prototype that consumes 76 mW and gives 32.3-dB SNDR with a Nyquist input at 40 GS/s, for 57-fJ/step FoMw.