Overloading in multistage sigma-delta modulators

Abstract

This paper presents a straightforward way to optimize scaling coefficients used in multistage (MASH) sigma-delta modulators. The scaling coefficients used to counter the effects of overloading are shown to be related to the reference voltage of the 1-bit D/A converter. Finally, an optimized 2-1-1 modulator with an extended dynamic range is proposed. This modulator uses a local feedback loop to extend the dynamic range (DR) to full-scale input level without overloading.