Triac-output optocoupler for AC load switching
The Vishay IL4218-X017T is a single-channel optoisolator with a triac output, designed to switch AC loads from a low-voltage control side while maintaining galvanic isolation. The 5300 Vrms isolation rating and 800 V off-state voltage make it suitable for line-voltage applications such as solid-state relays, motor starters, and industrial AC switching up to 277 VAC with healthy margin. Housed in a 6-SMD surface-mount package, it operates from -55°C to 100°C, covering industrial and some military-temperature environments.
The 5300 Vrms isolation voltage is a reinforced-grade rating for mains-isolated designs — enough for 240 VAC or 277 VAC line-to-control separation with safety margin for transient overvoltages. The 800 V off-state blocking voltage means the triac can hold off peak AC line voltage plus typical spikes without self-triggering. For a 240 VAC line (340 V peak), this gives over 2× derating. The 300 mA RMS on-state current covers small loads like contactor coils, indicator lamps, or solid-state relay input stages. The 10 kV/µs minimum static dV/dt is the critical spec for noisy environments — it prevents false turn-on from fast line transients, a common failure in industrial motor drives.
It is ROHS3 compliant, with approvals from BSI, CSA, cUR, FIMKO, UR, and VDE — covering North American and European safety certifications.