Triac-output optoisolator for resistive and inductive AC loads
The onsemi MOC3021SVM is a single-channel optoisolator with a triac output, rated for 4170 Vrms isolation between the LED input side and the output triac. The 400 V off-state voltage rating means it can directly drive the gate of a power triac or SCR on a 240 VAC line without an intermediate stage. The absence of a zero-crossing circuit (no internal zero-cross detection) allows phase-angle firing — the output can be triggered at any point in the AC cycle, which is the right choice for resistive heater control or soft-start where you need to vary the power by chopping the waveform.
Trigger current and drive margin
The maximum LED trigger current (Ift) is 15 mA, and the typical forward voltage (Vf) is 1.15 V. That means a standard 5 V logic output through a 220-ohm series resistor delivers about 17 mA — enough to saturate the LED and guarantee turn-on across temperature. The 100 µA typical holding current (Ih) means the output triac stays latched once triggered, even into a lightly inductive load that might otherwise drop below the holding threshold at the zero crossing.
Package, mounting, and board-level fit
Supplied in a tube and packaged in a 6-SMD gull-wing (6-SMD, Gull Wing) surface-mount package with a 6-SMD supplier device package designation. The gull-wing leads are coplanar and self-aligning during reflow — no through-hole staking required. The 6-pin footprint is shared across the MOC302x family, so a single PCB land pattern serves the MOC3021SVM, MOC3011SM, and MOC3073SVM variants without a layout change.
Listed as Active (current lifecycle stage) by onsemi. The part carries ROHS3 compliance and is approved under IEC/EN/DIN and UL standards — the UL mark is the one most North American panel builders require for a safety-isolated interface between a low-voltage controller and line-voltage AC loads.