800 V, 8 A RMS Snubberless™ triac for AC load switching
The STMicroelectronics T835-8G-TR is an 800 V, 8 A RMS Snubberless™ Alternistor triac in a D²PAK surface-mount package. Its Snubberless™ construction means the internal structure is designed to commutate inductive loads without an external RC snubber network — saving two to three passive components and the associated board area. This part targets AC mains switching for resistive and inductive loads up to 8 A continuous, such as heating elements, solenoid valves, small motors, and lighting ballasts.
The 800 V off-state voltage gives you headroom on 230 VAC or 277 VAC lines — the standard margin rule is 2x peak line voltage, so 800 V covers 277 VAC peak (392 V) with margin for transients. The 8 A RMS on-state current is the continuous rating; for motor or lamp inrush, the non-repetitive surge rating of 80 A at 50 Hz and 84 A at 60 Hz tells you the part can handle cold-filament or locked-rotor events. The 35 mA gate trigger current and 1.2 V gate trigger voltage are moderate — a 5 V logic output through a 100 Ω resistor can drive it, but a 3.3 V MCU pin will need a small NPN transistor or an optocoupler. The 35 mA holding current means the triac will stay latched once triggered as long as the load current stays above that threshold; for very light loads (below 35 mA), you may see dropout at zero-cross.
At 8 A RMS, expect significant self-heating; a thermal pad or via array under the tab is necessary to keep junction temperature below 125°C at full load.
For dual-sourcing, the closest pin-compatible alternative within the same ST T835 family is the T835-8G (non-tape-and-reel variant) — same die, same ratings, different shipping medium.