5000Vrms isolation in a 4-SMD Gull Wing package
The onsemi FOD817C3S is a single-channel optocoupler with a phototransistor output, rated for 5000Vrms isolation between input and output. That 5 kV isolation rating is the key spec for safety-barrier applications in AC mains-powered equipment — think switch-mode power supply feedback loops, PLC digital inputs, or motor-drive interface circuits where you need to break ground loops and pass a logic-level signal across a reinforced insulation barrier. The current transfer ratio (CTR) is specified as a minimum of 200% and a maximum of 400%, both measured at a forward current of 5 mA. This means with 5 mA through the IR LED, the output transistor can sink at least 10 mA — enough to drive a TTL/CMOS gate input directly without an extra buffer stage. The 200% floor also gives you headroom for LED degradation over temperature and lifetime.
Temperature range and switching speed for industrial use
Operating temperature spans -55°C to 110°C, which covers the full industrial range and reaches into the under-hood automotive zone. The output transistor is rated for 70 V maximum collector-emitter voltage and 50 mA continuous current.