Behavioral modeling of delta-sigma modulators

Abstract This paper presents an overview of DelSi, a MATLAB toolbox developed for the design and simulation of delta–sigma modulators. The DelSi toolbox can synthesize a stable noise-transfer function for complex network structures. The modelling tool consists of two c / c ++ programs, sdMod.c, a single stage delta–sigma modulator and firfilt.c, a decimating FIR filter. Cascaded modulators can be constructed using the programs as building blocks. The simulation tools support the inclusion of nonideal effects caused by circuit imperfections, such as amplifier finite open-loop gain, incomplete settling and saturation as well as capacitor ratio mismatches. Two design examples are presented: one for a 1–1–1 cascade and the other for a single-stage fifth modulator.