Active Schottky in a low-profile flat-lead package
The STPS3150UF is an active-production Schottky rectifier from STMicroelectronics, rated 150 V reverse and 3 A average forward current — a common choice for OR-ing, reverse-polarity protection, and freewheeling in 12-48 V DC rails where the 820 mV forward drop at 3 A sets the conduction loss floor.
Forward drop and leakage — the thermal budget
At 3 A the forward voltage is 820 mV max, so the conduction loss at full rated current is about 2.5 W — the SMBflat copper pad area under the cathode tab sets the junction-to-ambient thermal resistance, and the 175°C max junction temperature gives headroom for that dissipation if the board layout provides a decent copper pour. Reverse leakage is 2 µA at 150 V, which is the spec at 25°C junction — leakage doubles with temperature, so at 125°C junction it will be higher, and the thermal design should account for that self-heating.
Board-fit and rework reality
The SMBflat package has the same 2.9 mm × 4.6 mm footprint as a standard SMB but with flat leads instead of a J-bend — this means the solder joint is visible for inspection, and the part sits lower on the board.