4420Vrms isolation in a 6-DIP through-hole optocoupler
The SFH636 is a single-channel optocoupler from Vishay with a 4420Vrms isolation rating, a transistor output, and a DC input. It comes in a 6-DIP through-hole package (0.300" lead spacing), making it a fit for legacy through-hole designs, prototyping, and high-reliability hand-assembly where SMT is not preferred. The 300ns typical turn-on and turn-off times suit moderate-speed digital isolation up to a few MHz, while the 19% minimum current transfer ratio at 16 mA forward current ensures reliable logic-level translation across the barrier.
Switching speed and drive — what the 300 ns and 19% CTR mean
The 300 ns turn-on and turn-off times are symmetrical, which simplifies timing budget in pulse-width or data-isolation applications — you don't need to compensate for a lopsided propagation delay. The 19% CTR at 16 mA forward current means the output transistor can sink about 3 mA with that drive; for higher load currents, increase the LED current up to the 25 mA absolute maximum. The 400 mV Vce saturation at that current keeps the logic-low voltage well within TTL and 5V CMOS thresholds, answering the compatibility question: yes, the SFH636 works cleanly with 5V logic on the output side.
Temperature grade and environment
Rated for -55°C to 100°C operating temperature, this optocoupler covers industrial and military-temperature-range environments — outdoor telecom, motor drives, downhole instrumentation, and avionics bay equipment. The 4420Vrms isolation is a test voltage; for reinforced isolation applications, check the working voltage and creepage against your safety standard (IEC 60950, UL 1577). The through-hole DIP package is MSL 1 typically, but confirm the bake requirement if the original packaging has been opened.