800 V off-state, 12 A RMS — the phase-control workhorse
The STMicroelectronics TYN812TRG is a standard-recovery SCR in a TO-220-3 package, rated for 800 V off-state blocking and 12 A RMS on-state current. It is designed for AC phase-control applications such as motor speed controllers, lighting dimmers, and industrial power-switching circuits where the load is resistive or inductive.
Surge and trigger margins
Non-repetitive surge current is 145 A at 60 Hz (140 A at 50 Hz), which gives headroom for capacitor inrush or motor-start transients. Gate trigger current is 5 mA max, so it can be driven directly from a microcontroller I/O pin through a series resistor, simplifying the drive circuit. Hold current is 15 mA max — once triggered, the SCR latches on until the load current drops below this threshold, which is typical for line-frequency phase-control designs. Off-state leakage is 5 µA max, negligible in most power budgets.
The TO-220-3 package is through-hole, suited for board-level mounting with a heatsink tab that can be bolted to a chassis or clip-on heat spreader.