The Dynamic Element Matching Method for Sigma-Delta D/A and A/D Converters

When multi-bit quantizer is used in sigma-delta D/A and A/D converters, nonlinear error is produced in multi-bit switched capacitor DAC because of capacity mismatch. A method used to remove this nonlinear error is introduced in this paper. This method encodes the output of quantizer, and then the output can switch the switched capacitors in multi-bit switched capacitor DAC randomly, introducing random noise to smooth the nonlinear distortion. But the introduced random noise will raise the level of background noise in signal bandwidth. Considering that, the technique of noise-shaping is used in this method to put the noise in signal bandwidth out of signal bandwidth, expecting the improvement of the converters´ performance. A design example is presented in this paper, and the simulation result of the design indicates this method can remove the nonlinear error completely.