A second-order double-sampled delta-sigma modulator using individual-level averaging

摘要

A second-order double-sampled delta-sigma modulator is described. It uses all individual-level-averaging switching scheme to convert capacitor mismatch into high-pass noise. With a sampling rate of 25 MHz and an oversampling ratio of 128, the maximum measured signal-to-noise-and-distortion ratio is 82.2 dB, and the total harmonic distortion is -91.0 dB when the input is 2.5 dB below full scale. The modulator is fully differential, occupies 3.75 mm/sup 2/ in a 1.2-/spl mu/m CMOS process, and dissipates 25.9 mW (10.2 mW analog and 15.7 mW digital).