800 V reverse voltage — what it buys the design
The S3K-E3/9AT: The S3K-/9AT is a Vishay standard recovery rectifier rated for 800 V DC reverse voltage and 3 A average forward current, housed in a DO-214AB (SMC) surface-mount package. With a 2.5 µs reverse recovery time, it is a line-frequency rectifier — suited for mains input bridges, PFC boost stages, and DC bus pre-charge circuits where switching speed is not the constraint.
2.5 µs trr — standard recovery, not fast switching
The 2.5 µs reverse recovery time places this diode in the standard-recovery class (>500 ns). It handles 50/60 Hz rectification cleanly but will not work in a 100 kHz+ PFC or LLC converter where a fast or ultrafast diode (trr < 100 ns) is required. The 60 pF junction capacitance at 4 V is consistent with a slow-recovery die.
Junction temperature range and package
The DO-214AB (SMC) package provides a large cathode tab for heat sinking to the PCB copper plane; the 1.15 V forward drop at 2.5 A sets the conduction loss budget for thermal design.
It is ROHS3 compliant, which satisfies EU and most global regulatory requirements without exemptions.