800 V sensitive-gate SCR in a low-profile SMBflat-3L package
The ST TS110-8UF is a sensitive-gate silicon controlled rectifier (SCR) rated for 800 V off-state voltage and 1.25 A RMS on-state current, housed in a SMBflat-3L surface-mount package. The sensitive-gate characteristic — 100 µA maximum gate trigger current at 800 mV maximum gate trigger voltage — allows direct drive from a microcontroller I/O pin, an optocoupler output, or a low-power sensor circuit without an intermediate driver transistor.
The 800 V off-state voltage (Vdrm/Vrrm) gives you a comfortable derating margin for 230 VAC mains applications — the peak line voltage is about 325 V, so the 800 V rating covers transients and ring-wave events without needing a higher-voltage (and larger) device. The 1.25 A RMS on-state current (It(RMS)) is the continuous current the SCR can carry when fully conducting; the 800 mA average rating (It(AV)) is the more conservative figure for DC or half-wave loads. For a 230 VAC resistive load, 1.25 A RMS corresponds to roughly 290 W — a typical ceiling fan motor, a small pump, or a resistive heater element. The non-repetitive surge rating of 20 A at 50 Hz and 21 A at 60 Hz (Itsm) covers inrush from a motor start or a capacitor charge cycle, but the part is not intended for crowbar or high-energy pulse applications.
SMBflat-3L footprint and thermal considerations
The SMBflat-3L package is a low-profile, three-lead surface-mount package with flat leads — no gull-wing, no J-bend. The flat leads reduce the package height, which suits slim enclosures and single-sided PCB assemblies. The thermal path is through the leads and the small pad area; at 1.25 A RMS continuous, the junction temperature rise will be significant, so a copper pour on the cathode and anode pads is recommended. The part is ROHS3 compliant.