Oversampling Sigma-Delta Modulator Stabilized by Intensive Nonlinear Feedback Loop Technique

Abstract

Based on the former "Local Nonlinear Feedback Loop (LNFL)" technique for stabilization of oversampling Sigma-Delta Modulator (SDM), an improved technique called "Intensive Nonlinear Feedback Loop (INFL)" is proposed to further raise the stability. The INFL technique not only avoids the instability limitation of high-order SDM without SNR degradation like the former LNFL technique, but also suppresses the output swing range of the critical integrator more effectively than the former LNFL technique. The contribution significantly results from the stabilization scheme closer to the critical integrator. The proposed INFL technique can also be extended to apply to various configurations of SDMs, such as single-loop or multiple-loop structures, for robust-stability and low-power VLSI applications.