The Vishay VOS627A-4T is a single-channel phototransistor optocoupler in a 4-SOIC (4.40 mm width) surface-mount package. It provides 3750Vrms galvanic isolation between input and output, with a transistor output rated for 80 V and 50 mA per channel. The input accepts both AC and DC signals, which makes it useful for sensing AC line presence or bidirectional logic without an external rectifier bridge.
The 3750Vrms isolation rating is the key safety parameter for reinforced insulation in mains-connected equipment. It satisfies basic isolation requirements for 240 VAC line monitoring and many industrial bus interfaces (RS-485, CAN) where ground loops need breaking. For designs targeting IEC 60950-1 or IEC 62368-1, this rating supports basic isolation at working voltages up to around 300 VAC, but check creepage and clearance for your specific PCB layout — the 4-SOIC package provides about 4 mm creepage minimum.
CTR range and drive margin
The current transfer ratio is specified at 160% minimum and 320% maximum at a forward current of 5 mA. That means with 5 mA into the LED, the output transistor can sink at least 8 mA (160% of 5 mA) and at most 16 mA. For logic-level outputs, the 160% min ensures a clean low-side drive into a 10 kΩ pull-up to 5 V or 3.3 V. The 320% max matters when the input LED is driven hard — the output can saturate deeper, which reduces Vce(sat) but also increases switching times. If you need tighter CTR tolerance for gain matching across multiple channels, consider the binned versions in this family.
Switching speed — 3 µs rise/fall
Typical rise and fall times are 3 µs each, with turn-on time of 6 µs and turn-off time of 4 µs. This is adequate for data rates up to about 100 kbps or PWM frequencies up to 50 kHz. For higher-speed isolation (1 Mbps+), you would step up to a digital isolator or a logic-output optocoupler. The 3 µs edges are clean enough for most industrial sensor interfaces and relay drivers without extra Schmitt triggering.
Package and rework — 4-SOIC/SSOP
The VOS627A-4T comes in a 4-SOIC package (0.173" body width, 4.40 mm) also referred to as 4-SSOP. It is a surface-mount part with a 1.27 mm pitch — easy to hand-solder with fine tweezers and a temperature-controlled iron. Under hot air, the small thermal mass means it reflows quickly; set the nozzle to 300°C at low airflow and it lifts clean in about 5 seconds. No exposed pad, so no via-stitch thermal management needed.
Lifecycle and compliance
RoHS compliance is standard for Vishay optocouplers in this series; confirm the specific date-code compliance certificate if your QA requires it.