What is the difference between SMF5.0A and SMAJ5.0A?

The two parts differ in both package and power rating. The SMF5.0A uses a SOD-123FL package (2.9mm × 1.9mm) with a 200W peak pulse power rating, while the SMAJ5.0A uses a larger SMA / DO-214AC package (4.6mm × 2.8mm) with a 400W rating. The SMF5.0A saves approximately 40% PCB footprint area, making it better suited for space-constrained portable designs. The SMAJ5.0A offers double the surge power handling but requires more board space.