What this optoisolator brings to the board
The Vishay VOM618A-3T is a single-channel DC-input optocoupler with a phototransistor output, rated for 3750 Vrms isolation between primary and secondary sides. The current transfer ratio (CTR) is specified at 100% minimum and 200% maximum when you drive the LED at 1 mA forward current, which means even a weak 3.3 V logic signal through a series resistor can saturate the output transistor. The 80 V output voltage ceiling and 50 mA per-channel current give you headroom for driving relays, PLC inputs, or level-shifting industrial logic lines.
CTR and 3.3 V logic — will it switch cleanly?
Yes, the VOM618A-3T works with 3.3 V logic. The LED forward voltage is typically 1.1 V, so a 3.3 V output through a 220 Ω to 470 Ω resistor lands near 1 mA forward current. At that drive level the CTR is guaranteed between 100% and 200%, so the output transistor can sink the load current without hanging in the linear region. The turn-on time is 7 µs typical, turn-off 6 µs — fast enough for most 10 kHz to 50 kHz switching applications like inverter gate drives or sensor readback.
Where it fits — temperature and environment
Rated from -55°C to 110°C operating temperature, this part handles cold-start in outdoor enclosures and the heat inside a motor control cabinet. The 3750 Vrms isolation is suited for reinforced insulation in industrial AC mains circuits (up to 300 V working voltage typically), and the 4-SOP package gives you 8 mm creepage distance between input and output pins — enough for basic safety isolation in many designs.
Lifecycle and compliance
No last-time-buy or successor has been announced.