What this quad optocoupler gives you
The ILQ621 from Vishay packs four independent optocoupler channels into a single 16-DIP through-hole package. Each channel uses a phototransistor output with a DC input LED, rated for 5300Vrms isolation between input and output sides. That isolation rating is the headline number for this part — it qualifies the ILQ621 for industrial and power-conversion applications where galvanic isolation is a safety or noise-rejection requirement, such as PLC digital inputs, motor-drive feedback, and AC-mains monitoring circuits. Each of the four channels can handle up to 50mA output current and 70V across the output transistor, with a typical Vce saturation of 400mV. The current transfer ratio (CTR) spans from 50% minimum to 600% maximum at a forward current of 5mA, giving the designer a wide operating window for logic-level translation across the isolation barrier.
That makes the ILQ621 suitable for 10-100 kbps data rates or relay-coil drive, not high-speed serial isolation.
Through-hole 16-DIP with 0.300" (7.62mm) body width — a standard DIP footprint that fits existing board layouts for industrial I/O modules. No MSL concern for through-hole parts; standard wave-solder profile applies.