Active production — no end-of-life clock ticking
NXP lists the ACTT4X-800C,127 as Active. No last-time-buy window, no successor part number to track. This triac is a stable BOM line for ongoing builds, not a shortage-driven swap.
4 A RMS at 800 V — what the ratings mean for the load
The 4 A RMS on-state current sets the continuous load ceiling. For a resistive heater or incandescent lamp at 230 VAC, that is roughly 920 W steady-state. The 800 V off-state voltage gives enough blocking margin for 277 VAC mains with the usual line transients — no external snubber needed for most resistive loads. Gate trigger is specified at 35 mA max with a 1 V max threshold. Standard 5 V logic or an opto-triac driver (MOC30xx series) can fire it directly without a separate driver transistor. The 35 mA hold current means the triac stays latched once triggered down to about 35 mA of load current — below that it commutates off, which is typical for standard triacs in AC phase-control. Non-repetitive surge rating is 39 A at 60 Hz and 35 A at 50 Hz. That covers the inrush from a 100 W tungsten filament lamp or the start-up surge of a small universal motor. If the load has a capacitor-input supply, the peak charging current can exceed this — budget a soft-start or series NTC thermistor.
TO-220F isolated tab — no mica washer needed
The TO-220-3 Full Pack (TO-220F) package has a fully isolated metal tab. That saves assembly time and eliminates one thermal interface joint. The through-hole leads suit point-to-point wiring or PCB mounting with the standard 2.54 mm pitch footprint.
125°C junction — industrial ambient envelope
Rated for a maximum junction temperature of 125°C. In a 70°C ambient enclosure with natural convection, the junction-to-ambient thermal resistance of the TO-220F package (roughly 60°C/W without a heatsink) limits dissipation to about 0.9 W — at 4 A RMS the on-state voltage drop of a standard triac is around 1.3 V, so 4 A × 1.3 V = 5.2 W requires a heatsink.