A Low-OSR 5th-Order Noise Shaping SAR ADC Using EF-EF-CIFF Structure with PVT-Robust Differential V-T-V Converter

This paper presents a low-OSR 5th-order noise-shaping (NS) SAR (NS-SAR) ADC featuring a differential-Voltage-Time-Voltage (dVTV) converter. It introduces an innovative EF-EF-CIFF structure that achieves 5th-order NS with only two amplifications using the proposed dVTV converter. The PVT-robust dVTV converter enables the optimization of the Noise Transfer Function (NTF) without the need for static-power consumption, gain calibration, and trimming banks, thereby reducing circuit complexity and power consumption. The ADC has been prototyped and verified in 40nm CMOS technology with an active area of 0.059mm2. Operating at a supply voltage of 1.1V and a sampling rate of 5MS/s, it achieves an SNDR of 81.8dB over a 625kHz bandwidth. The resulting Schreier Figure of Merit (FoMs) and Walden FoM (FoMw) are 181.8dB and 7.2fJ/conversion-step, respectively.