5300Vrms isolation in a 4-DIP through-hole package
The Vishay SFH617A-1 is a 1-channel phototransistor optocoupler in a 4-DIP through-hole package, providing 5300Vrms of galvanic isolation between input and output. It is built for industrial power supplies, motor drives, PLC I/O modules, and any application where a clean isolation barrier is needed between a low-voltage control side and a higher-voltage load side. The DC input drives an infrared LED, and the phototransistor output can switch up to 70V at 50mA per channel.
The current transfer ratio (CTR) is specified at 40% minimum and 80% maximum, both measured at a forward current of 10mA. This means at 10mA input, the output transistor can sink between 4mA and 8mA — a wide spread that the designer must budget for in the pull-up resistor and threshold logic. The typical turn-on time is 3µs and turn-off time is 2.3µs, with rise and fall times of 2µs each. These switching speeds are adequate for 50/60 Hz line-sync detection, relay drivers, and low-speed digital isolation up to about 100 kbps, but not for high-speed data links.
Temperature range and operating limits
The 70V output breakdown and 50mA continuous output current give solid headroom for 24V industrial logic and relay coils. Forward voltage is typically 1.35V, with an absolute maximum forward current of 60mA — a standard 330Ω series resistor from a 5V logic rail lands near 11mA, right in the CTR test condition sweet spot.