RuggedCircuits:
The LM2575 is not a drop-in substitute -- it is a switching regulator controller, just one component of a switching regulator. You still need to add an inductor, diode, and capacitors around it, and route it properly on a PCB to keep the switching loop tight, etc.
Understood; I hadn't meant to suggest that it was a drop-in replacement. The data sheet makes it clear what extra components are required.