Triac-output optoisolator for AC load switching
The onsemi FOD410SD is a single-channel optoisolator with a Triac output, designed to switch AC loads directly from a low-voltage logic or microcontroller signal. The zero-crossing circuit turns the Triac on near the AC zero-voltage point, reducing inrush current and EMI at switch-on. Rated for 5000Vrms isolation and 600 V off-state voltage, it suits motor starters, solid-state relays, and industrial PLC output modules where galvanic isolation between control and power is mandatory.
Switching speed and noise immunity
Turn-on time is 60 µs, fast enough for 50/60 Hz line-cycle switching but not intended for high-frequency PWM. The minimum static dV/dt of 10 kV/µs prevents the Triac from false-triggering on fast voltage transients from inductive loads or mains-borne noise. Maximum LED trigger current is 2 mA, allowing direct drive from 3.3 V or 5 V logic outputs without a buffer transistor. Hold current is 500 µA — the Triac latches once triggered and only turns off when the load current drops below that threshold near the AC zero crossing.
Package and compliance for production
It comes in a 6-SMD gull wing package on Tape & Reel or Cut Tape, suitable for reflow assembly. CSA and UL approvals simplify safety certification in end equipment. Operating temperature range is -55°C to 100°C, covering industrial and outdoor applications. The 1.25 V typical forward voltage and 30 mA max forward current define the LED drive circuit — a series resistor from the logic supply is all that is needed.