5300Vrms isolation — where this optocoupler fits
The Vishay SFH640-2 is a single-channel phototransistor optocoupler with a base connection, packaged in a 6-DIP through-hole housing (0.300" pin spacing). Its 5300Vrms isolation rating puts it in the class used for reinforced insulation in motor drives, industrial PSU feedback loops, and PLC digital input modules — anywhere you need to pass a DC-level signal across a safety barrier without galvanic coupling.
The current transfer ratio is specified at 63% minimum to 125% maximum, both measured at 10 mA forward current. That 2:1 spread is tight enough that you can pick a single load resistor value and still guarantee the output saturates across temperature and device-to-device variation — no need to bin or overdrive the LED. The transistor-with-base output (pin 6) lets you pull the base low to force the output off faster, or add a speed-up capacitor between base and collector to shave the 5.5 µs fall time.
300V output — not just a logic-level switch
Rated Vce(max) of 300V means the output transistor can switch 48V or 120V DC rails directly, not just 5V or 24V logic. If you need more current, the base-drive access lets you add an external transistor stage without a second optocoupler.
The 6-DIP through-hole package is a standard 7.62 mm pitch — no special footprint, easy to hand-assemble or wave-solder. The base connection is the sixth pin; if you are replacing a 4-pin optocoupler, the extra pin needs a pad or a no-connect.
It is ROHS3 compliant.