3750Vrms isolation in a 4-SSOP package
The Vishay VOS617A-9T is a single-channel DC-input transistor-output optocoupler rated for 3750Vrms isolation in a 4-SSOP surface-mount package. The current transfer ratio spans 200% to 400% at 5mA forward current, giving you a wide operating margin for driving logic inputs, PLC digital I/O, relay coils, or isolated feedback loops in power supplies. The output transistor handles up to 80V and 50mA continuous, with a typical Vce(sat) of 400mV — low enough to keep dissipation under control in a 4-pin SOIC footprint.
Switching speed and drive margin
Rise and fall times are both 3µs typical; turn-on time is 6µs, turn-off 4µs. That limits the practical data rate to roughly 100 kHz — fine for 50/60 Hz mains zero-crossing detection, slow PWM for heater control, or serial interfaces like 9600 baud RS-232 isolation. For faster switching (e.g., 1 MHz gate drive) you would need a logic-output optocoupler with a different CTR/speed trade-off. The 200% minimum CTR at 5mA means the LED drive current can be as low as 2.5 mA and still guarantee the output saturates into a 5V logic load with a 10k pull-up. At the 400% max end, the same 5mA input can drive a 1k load or a relay coil directly, though you should check the 50mA output current ceiling against your load.
Temperature range and environment
The 4-SSOP package is a compact footprint for dense PCB layouts, but the 110°C upper limit means you should derate the output current if the ambient near the part exceeds 85°C — the 50mA absolute maximum assumes the package can dissipate the heat.