4170Vrms isolation in a 6-DIP — what it buys you
The onsemi 4N35M is a 1-channel phototransistor optocoupler with a base pin, packing 4170Vrms of isolation into a standard 6-DIP through-hole package. That isolation rating covers reinforced insulation per IEC 60950-1 for mains-referenced circuits — think offline power supplies, motor-drive feedback, or PLC digital inputs where the controller side must stay galvanically separated from the field wiring. The 100% minimum current transfer ratio at 10 mA forward current means the output transistor saturates reliably when driving a typical 5 V logic input or a microcontroller GPIO — no external transistor stage needed. With a typical 2 µs turn-on and turn-off time, it handles switching up to about 100 kHz before the propagation delay eats into the duty cycle margin.
Temperature grade and board-fit for the reflow engineer
The through-hole 6-DIP (0.300-inch row spacing) is a legacy footprint — it survives wave solder fine, but if your line runs reflow-only, this part needs a selective-solder or hand-solder step. The tube packaging means no tape-and-reel feeder; plan for tube-fed or manual placement on the pick-and-place line. The output transistor saturates at 300 mV max, leaving good noise margin for downstream logic thresholds.