Isolation and signal-transfer parametrics
Rated for 3750Vrms isolation, the SFH691AT accepts both AC and DC input drive and provides a transistor output — a common configuration for digital signal isolation in industrial controls, PLC I/O modules, and power-supply feedback loops. The current transfer ratio spans 50% minimum to 300% maximum at 5 mA forward current, giving the designer a predictable gain window for logic-level translation across the isolation barrier. Switching speed is specified with a typical rise time of 3 µs and fall time of 4 µs, and turn-on/turn-off times of 5 µs and 3 µs respectively — fast enough for 100 kHz data rates in most isolated serial interfaces or gate-drive feedback paths. The output can sink or source up to 50 mA continuously, with a maximum collector-emitter voltage of 70 V.
Housed in a 4-SOP Gull Wing package (supplier device package 4-SOP with 2.54 mm lead pitch), the SFH691AT is a surface-mount optoisolator that fits standard reflow profiles. The 4-SMD Gull Wing footprint is common across many Vishay optocouplers, simplifying PCB layout and second-source qualification.
Temperature grade and environment
Operating temperature range of -55°C to +100°C covers industrial and outdoor telecom enclosures. The 1.15 V typical forward voltage at 50 mA max forward current keeps the LED drive circuit within standard logic supply rails. Maximum Vce saturation of 300 mV ensures low output voltage drop when the transistor is fully on.