A 320-MHz NS TD-ADC-Assisted C/DT Hybrid Pipelined ADC With Single OTA Second-Order RAF

This article presents a noise-shaping time-domain analog-to-digital converter (NS TD-ADC)-assisted continuous/discrete time (C/DT) hybrid pipelined ADC architecture in conjunction with a single operational transconductance amplifier (OTA) second-order residue amplifying filter (RAF), facilitating high power efficiency at wideband target. Besides, using a high-speed NS TD-ADC as the 1st-stage sub-quantizer (QTZ) effectively suppresses the tonal behavior due to the low-resolution residue. The RAF exploits the single-amplifier biquad (SAB)-based structure to realize a single OTA second-order filtering, thus simplifying the design and preserving high energy efficiency. The backend DT QTZ is with $2{\times }$ time-interleaved (TI), which eases the compromise between speed and power efficiency in the CT pipelined (CT Pipe) ADC design. Fabricated in a 28-nm process, the design obtains 65.4-dB signal-to-noise and distortion ratio (SNDR) with 320-MHz bandwidth while consuming 56.17 mW from 1.4- to 0.95-V power supplies. The prototype exhibits a dynamic range of 68 dB with a Schreier figure of merit (FoM) of 163 dB, demonstrating a high power efficiency under 2.4-GHz sampling frequency.