LTC SwitcherCAD™ III is a fully functional Spice III simulator with enhancements and models for easing the simulation of switching regulators.
This Spice is a high performance circuit simulator, integrated waveform viewer, which also includes schematic capture. Our enhancements to Spice have made simulating switching regulators extremely fast compared to normal Spice simulators. Included in this download are Spice, Macro Models for 80% of Linear Technology's switching regulators and over 200 op amp models.
Furthermore, resistors, transistors and MOSFET models are included as part of this package. With this Spice simulation, viewing of the waveforms of most switching regulators can be achieved in a few minutes on a high performance PC. Also, full circuits using op amps or transistors can easily be simulated.
I tested it out as well as some of my engineer friends and its good!