800 V blocking, 25 A RMS — a workhorse SCR in an isolated package
The Vishay VS-25TTS08FP-M3 is a standard-recovery SCR (silicon-controlled rectifier) rated for 800 V off-state blocking voltage and 25 A RMS on-state current, with a 16 A average current capability. It comes in the fully molded TO-220AB Full-Pak (TO-220-3 Full Pack) — the plastic body extends over the mounting tab, so the tab is electrically isolated. That saves the insulating washer and thermal compound normally needed with a metal-tab TO-220, and it simplifies heatsink mounting in equipment where the heatsink is chassis-grounded or shared across multiple devices. Typical applications include AC motor drives, power supplies, battery chargers, lighting ballasts, and industrial heating controllers where a phase-controlled rectifier or AC switch is needed.
Surge current and gate trigger — sizing the drive and the protection
The non-repetitive surge current is 270 A at 50 Hz half-sine wave — that is the peak the die can survive for one cycle during a fault or inrush event. For a motor-start or capacitor-precharge circuit, this number drives the fuse or circuit-breaker coordination: the protection must open before the surge exceeds the SCR's I²t capability. The gate trigger current is 45 mA maximum, and the gate trigger voltage is 2 V maximum, which is compatible with standard optocoupler or pulse-transformer drive circuits. Holding current is 150 mA — if the load current drops below that, the SCR will commutate off at the next zero-crossing. Off-state leakage is 500 µA at rated voltage, which matters for standby power budgets in mains-powered equipment.
Temperature range and thermal design
The Full-Pak package has a higher thermal resistance than a standard TO-220 with a metal tab, so the heatsink must be sized accordingly — expect to derate the continuous current if the ambient is above 70°C or if airflow is limited. The on-state voltage drop is 1.25 V maximum at rated current, which sets the conduction loss that the heatsink must dissipate.
ROHS3 compliant.