A multi-bit sigma-delta modulator and new DWA used in an audio DAC

Sigma-Delta Modulator plays an important part in the Sigma-Delta DAC. This paper describes a high order multi-bit low-pass Sigma-Delta modulator and a DEM (Dynamic Element Matching) applied in a 24-bit audio DAC. We apply a new array DWA in the DEM to reduce the influence of DAC nonlinearity error. The low-pass modulator can transfer the noise out of the audio band, so that it can improve the in-band SFDR. The modulator is a 4-order 4-bit optimized CIFF (Cascade Integrators Feed Forward) structure, the in-band SFDR and THD can get to about 137dB and -129dB in the ideal situation 114dB and -104dB in the worst situation. We design it aided by the Matlab&Simulink and have done some optimizations before the implementation. The performance of this modulator can meet the audio specifications.