Active production, 800 V / 4 A sensitive-gate TRIAC
The ACST410-8BTR from STMicroelectronics is an active-production, logic-level sensitive-gate TRIAC rated for 800 V off-state and 4 A RMS on-state continuous current. Holding current is 20 mA maximum, which means the TRIAC latches on once triggered and stays conducting until the load current drops below that threshold — relevant for low-wattage loads that might not sustain conduction through a full half-cycle.
DPAK footprint and thermal budget
The junction temperature range spans -40 °C to 125 °C, covering industrial enclosures and warm-ambient environments where the self-heating from 4 A RMS conduction plus ambient heat must stay under the 125 °C ceiling. Surface-mount assembly on standard reflow profiles; the DPAK tab is the thermal path — copper-pour area on the PCB landing pad sets the effective thermal resistance, not the package alone.
Surge capability and load type
Non-repetitive surge current is 30 A at 50 Hz and 32 A at 60 Hz — this is the inrush the TRIAC can clear once without damage, relevant for capacitive loads (power supplies, LED drivers) or incandescent lamp cold-filament surges. The sensitive-gate classification means the gate is more susceptible to dV/dt false-triggering from line transients than a standard-gate TRIAC — a snubber across the MT1-MT2 terminals is good practice when switching inductive loads like small motors or solenoids.
Compliance and sourcing posture
ROHS3 compliant — no restricted substances in the bill of materials, covering EU RoHS directive exemptions through 2024.