A VTC/TDC-Assisted 4× Interleaved 3.8 GS/s 7b 6.0 mW SAR ADC With 13 GHz ERBW

Abstract

Compact, high-bandwidth analog-to-digital converters (ADCs) with moderate resolution are a critical building block in high-speed communication links. In this work, a hybrid time and voltage domain ADC is presented that uses a single high-speed voltage-to-time converter (VTC) as a high-bandwidth sampling buffer for a four-way time-interleaved successive approximation (SAR) ADC. Time-domain encoding also enables a low-power 3b SAR assist time-to-digital converter (TDC) to enhance SAR speed with minimal calibration. A 0.0045 mm2 prototype fabricated in 22 nm fin field-effect transistor (FinFET) CMOS provides 13 GHz effective resolution bandwidth (ERBW) and consumes 6.0 mW with a Nyquist signal-to-noise-and-distortion ratio (SNDR) of 38 dB at 3.8 GS/s, for 24.4 fJ/step Walden FoM.