The STPS20SM80CG-TR is a dual Schottky rectifier from STMicroelectronics, configured as a common-cathode pair in a D²PAK (TO-263AB) surface-mount package. This part is a Schottky, not a fast-recovery diode — the 500 ns recovery spec is a catch-all category, not a meaningful switching parameter; the real advantage is the low Vf and negligible reverse-recovery charge in continuous-conduction-mode PFC or output rectification.
ST lists the STPS20SM80CG-TR as obsolete. If this part is on your BOM, you are buying new-old-stock or pulled inventory. There is no official ST successor listed, so a drop-in replacement from the same manufacturer is not guaranteed.
Dual common-cathode — board-level fit
The common-cathode pair means the two anodes are separate, the cathodes are tied together internally. That maps directly to center-tapped transformer secondaries, dual-output forward converters, or OR-ing diodes where the cathodes share a common rail. At 10 A per diode continuous, the tab-to-ambient thermal resistance of the board determines whether the junction stays under 175°C. The 25 µA reverse leakage at 80 V is typical for a Schottky of this voltage class; it doubles with temperature, so at high junction temperatures the leakage contribution to self-heating needs a quick check.