Modeling of a Chopper Drive in Matlab/Simulink?

Has anyone had success modeling a chopper drive for stepper motors in Simulink? We are trying to model the behavior of an Allegro A4982 driver board. For example, we would like to be able model the different current modulation levels based on the driver spec for different stepping sequences (1/2 step, 1/4 step, 1/8th step). We are using this in conjunction with our stepper motor model to validate that we can generate a torque speed curve in simulation. Thanks