3750Vrms isolation — the spec that defines the part
The VOMA617A-3X001T is a single-channel phototransistor optocoupler from Vishay's VOMA617A series, built for basic galvanic isolation in a compact 4-SOP gull-wing package. Its 3750Vrms isolation rating covers the typical reinforced-single insulation requirement for mains-referenced power supplies, motor drives, and industrial PLC I/O modules. The DC input side drives an infrared LED (typical forward voltage 1.33V, max forward current 20 mA), and the output is a phototransistor rated to 80 V and 50 mA continuous — enough to switch a logic input, drive a small relay coil, or level-shift a 5V signal. Current transfer ratio is binned at 100% minimum, 200% maximum at a 5 mA forward current, so you get consistent drive margin across the reel.
CTR bin and switching speed — the selection numbers
The 100–200% CTR range at 5 mA If means the output transistor saturates with about 5–10 mA of base drive at that forward current, leaving headroom for the 50 mA output ceiling. Rise and fall times are 2.3 µs and 3.2 µs typical; turn-on and turn-off times run 4.9 µs and 3.3 µs. That puts this part in the medium-speed class — fine for 10–100 kHz switching in isolated feedback loops, relay drivers, or status-signal transmission, but not for high-speed data isolation. The 400 mV Vce saturation max at the rated output current keeps dissipation low in the on-state.
–40°C to 110°C — industrial temperature coverage
The 4-SOP package is rated for surface-mount reflow; the gull-wing leads give good solder-joint inspection access and some compliance for thermal cycling on FR4.