The Vishay VOS615A-X001T is a single-channel phototransistor optocoupler in a compact 4-SSOP surface-mount package. It provides 3750 Vrms galvanic isolation between a DC input LED and a transistor output, with a minimum current transfer ratio of 40% and a maximum of 600% at 10 mA forward current. The wide operating temperature range from -55°C to 110°C suits it for industrial control, motor drive feedback, and power-supply isolation where the board sees temperature swings from cold start to full load.
The 3750 Vrms isolation voltage is the primary safety rating — it meets basic reinforced isolation requirements for many 240 VAC mains-powered designs. The output transistor is rated for 80 V maximum collector-emitter voltage and 50 mA continuous current, which covers typical logic-level interface and low-side switching tasks. The 400 mV Vce saturation at the output ensures the logic low level stays well below the 0.8 V threshold for TTL inputs, even with the LED driven at the minimum CTR.