Triac output coupler for AC load switching
The Toshiba TLP266J(V4T7TR,E is a single-channel triac output optocoupler in the TLP series, designed for driving AC loads through isolated gate control. It integrates a zero-crossing detection circuit that turns on the output triac only when the AC mains voltage crosses zero, which reduces inrush current and radiated EMI when switching resistive loads like heaters, solenoids, or incandescent lamps. The part provides 3750Vrms isolation between the LED input and the triac output, making it suitable for applications where safety isolation is required between a low-voltage controller and a 120 VAC or 240 VAC power circuit. The output is rated for 600 V off-state blocking voltage and can handle 70 mA RMS on-state current, which covers direct drive of small AC loads or gate drive of a larger external triac or SSR. The static dV/dt rating of 200V/µs minimum ensures the output does not falsely trigger from fast voltage transients common on industrial AC lines — a critical parameter for motor-drive and contactor environments where noise is present.
The zero-crossing circuit fires the output triac within a few volts of the AC zero crossing, so the load sees a soft start each half-cycle. This cuts the EMI filter bill — you can often skip a series inductor that a random-turn-on triac would need. The trade-off is that zero-crossing parts are not suitable for phase-control dimming or soft-start circuits that require variable firing angles; for those, pick a non-zero-crossing triac coupler. The LED trigger current (Ift) is 10 mA maximum, with a typical forward voltage of 1.27 V. The hold current (Ih) is 600 µA typical, which means the output stays latched once triggered as long as the load current exceeds that threshold; below it the triac drops out at the next zero crossing.
Package and temperature range for industrial builds
The 3750Vrms isolation rating meets basic reinforced insulation requirements for mains-connected equipment per IEC 60950-1 and IEC 62368-1, which simplifies safety certification.