A 12b 100 MS/s Three-Step Hybrid Pipeline ADC Based on Time-Interleaved SAR ADCs

Abstract

This work proposes a 12b 100 MS/s 0.11 μm CMOS three-step hybrid pipeline ADC for highspeed communication and mobile display systems requiring high resolution, low power, and small size. The first stage based on time-interleaved dualchannel SAR ADCs properly handles the Nyquist-rate input without a dedicated SHA. An input sampling clock for each SAR ADC is synchronized to a reference clock to minimize a sampling-time mismatch between the channels. Only one residue amplifier is employed and shared in the proposed ADC for the first-stage SAR ADCs as well as the MDAC of back-end pipeline stages. The shared amplifier, in particular, reduces performance degradation caused by offset and gain mismatches between two channels of the SAR ADCs. Two separate reference voltages relieve a reference disturbance due to the different operating frequencies of the front-end SAR ADCs and the back-end pipeline stages. The prototype ADC in a 0.11 μm CMOS shows the measured DNL and INL within 0.38 LSB and 1.21 LSB, respectively. The ADC occupies an active die area of 1.34 mm² and consumes 25.3 mW with a maximum SNDR and SFDR of 60.2 dB and 69.5 dB, respectively, at 1.1 V and 100 MS/s.