Device identity and key isolation specs
The onsemi 4N35300W is a single-channel optoisolator with a phototransistor output and base pin access, in a 6-pin DIP package (0.400-inch body width, 10.16 mm row spacing). The 5300 Vrms isolation rating qualifies it for reinforced insulation in mains-connected circuits — think AC-line monitoring, power-supply feedback, or motor-drive interface isolation where the primary-to-secondary voltage differential demands a guaranteed withstand margin. The DC input side drives an infrared LED at a forward voltage of 1.18 V typical; the output transistor can handle up to 30 V collector-emitter with a saturation voltage of 300 mV max. Switching is symmetrical at 2 µs turn-on and turn-off typical, which keeps the part usable for low-speed digital isolation up to roughly 250 kbit/s — fine for 50/60 Hz zero-crossing detection, relay drivers, or PLC digital input isolation.
Lifecycle reality and sourcing note
The 4N35300W is listed as Obsolete by onsemi. If the BOM calls for this exact DIP-6 footprint and 5300 Vrms isolation, the replacement path is a board-spin to a current-production optocoupler family — no pin-compatible drop-in exists from onsemi.
The through-hole DIP-6 package (0.400-inch body, 10.16 mm row spacing) mates with standard 0.100-inch pitch sockets or solders directly into a plated-through-hole PCB.