4 A RMS sensitive-gate SCR for 240 VAC line switching
The TS420-600T is a sensitive-gate SCR rated for 600 V off-state blocking and 4 A RMS on-state current in a TO-220 package — sized for phase-control and AC-switching circuits where a low gate trigger current simplifies the drive stage. With a maximum gate trigger current of 200 µA and gate trigger voltage of 800 mV, this SCR can be driven directly from a microcontroller I/O pin, a low-power Hall-effect sensor, or a simple transistor stage without a separate driver IC.
On-state and surge ratings — what they mean for the circuit
The 2.5 A average (IT(AV)) and 4 A RMS (IT(RMS)) on-state current ratings define the continuous load the SCR can carry in a half-wave or full-wave rectifier, a heater controller, or a small motor speed-control circuit — the RMS figure governs the thermal stress from the conduction angle, not just the DC average. Holding current is 5 mA maximum, and off-state leakage is 5 µA maximum — the low holding current means the SCR stays latched once triggered even with a light load, while the low leakage at 600 V off-state keeps standby power loss negligible in a switched-mode or capacitive-discharge circuit.
Package and thermal integration
The TO-220-3 (supplier device package TO-220) is a standard through-hole power package with a metal tab — the tab is electrically common with the cathode (pin 2) in most SCRs, so the heatsink must be isolated or the tab must be electrically floating if multiple devices share a common heatsink.
ROHS3 compliant — the part meets the current RoHS directive for lead-free soldering and restricted substance limits, which is required for CE-marked equipment sold in the EU and for most commercial electronics manufactured after 2015.