Simulating sigma-delta modulators in AWEswit

The paper describes the modeling and simulation of switched capacitor sigma-delta modulators in AWEswit. AWEswit is a mixed signal simulator for switched capacitor circuits that merges electrical circuit simulation with event driven logic simulation. It employs asymptotic waveform evaluation (AWE) as its core simulation engine. Mixed level modeling of the circuit components is facilitated by AWEswit´s ability to combine formulations in the current voltage and charge voltage regimes. AWEswit naturally handles the linear bandwidth limitations associated with switched capacitor circuits. Here, AWEswit´s approach to modeling the clock feedthrough and signal dependent charge dump that characterize MOSfet switches is described. In addition, a postprocessing technique to superimpose the effect of component nonlinearity on the linear AWEswit solution is presented.