Accurate multi-bit feedback DAC dedicated to high-speed Continuous-time ?? converters

This paper presents the behavioral modeling and circuit design of an accurate multi-bit DAC dedicated to high-speed Continuous-time ΔΣ converters. The multi-bit DAC element mismatch is modeled, demonstrating that the non-linearities coming from the feedback DACs is awful for Continuous-time ΔΣ modulators. The proposed DAC is dimensioned in order to achieve best matching, reaching an unit current source relative standard deviation up to 0.7%. A full high-speed Continuous-time ΔΣ converter is implemented using the accurate DAC, achieving a SNR of 76 dB in a widebandwidth of 20 MHz.