3750Vrms isolation in a 4-SOP package
The Vishay SFH1690CT is a single-channel DC-input optocoupler with a transistor output, rated for 3750Vrms isolation voltage. It comes in a 4-SMD gull-wing package (4-SOP supplier package), surface-mount only. The current transfer ratio (CTR) is specified at 100% minimum and 200% maximum when driven at 5mA forward current — a tight enough window to design a reliable logic-level interface without over-specifying the LED drive.
Switching speed and output drive
That puts this part in the general-purpose isolation class — fine for 10–100 kHz digital signals, relay drivers, or PLC input modules, but not for high-speed serial links. The output transistor can sink up to 50mA and withstand 70V across the collector-emitter, with a maximum saturation voltage of 400mV at rated current.
Temperature range and forward characteristics
The typical forward voltage is 1.15V, and the absolute maximum DC forward current is 50mA — keep the LED drive within that limit to avoid degrading the CTR over time. ROHS3 compliant per the listing.
For dual-sourcing or a pin-compatible second source, the SFH1690 (without the 'CT' suffix) shares the same 4-SOP footprint and 3750Vrms rating, though its CTR bin may differ — verify the CTR range against your design margin.