75 ns trr — the spec that makes this a fast-recovery diode
The STTH310S is a 1000 V, 3 A standard fast-recovery diode from STMicroelectronics, housed in a DO-214AB SMC package. Its 75 ns reverse recovery time places it squarely in the fast-recovery class, not a standard 50/60 Hz rectifier — that trr is what lets it switch at tens of kilohertz without hammering the MOSFET or IGBT with reverse-recovery losses.
1000 V blocking with 3 A average — where it lands on the BOM
At 1000 V reverse and 3 A forward average, this diode fits primary-side boost stages in power-factor-correction circuits for off-line supplies up to about 300 W, and secondary-side freewheeling in flyback converters where the reflected voltage can hit 800 V. The 1.7 V forward drop at 3 A is the conduction-loss number to budget — at 25 °C it's 1.7 V, and it rises with junction temperature, so the thermal loop needs to account for the Vf increase at operating Tj.