A second-order double-sampled delta-sigma modulator

A second-order double-sampled delta-sigma modulator (DSM) is described. It uses an additive-error switching scheme to convert capacitor mismatch into an additive out-of-band tone that can be removed by a digital filter. At a clock rate of 1.25 MHz and with an oversampling ratio of 256, the maximum measured signal-to-noise-and-distortion ratio is 89.8 dB, and the THD is -96.6 dB when the input is 2 dB below full scale. The modulator is fully differential, occupies 5 mm/sup 2/, and dissipates 13 mW.