5300Vrms isolation — the application driver
The SFH618A-3X017 is a Vishay single-channel transistor-output optocoupler that delivers 5300Vrms galvanic isolation between input and output. That isolation rating puts it squarely in industrial and power-conversion designs — motor drives, switched-mode power supply feedback loops, PLC digital inputs, and any interface where a 50/60 Hz mains or DC-bus voltage must be kept off the control logic. The transistor output is the workhorse topology: simple to bias, no external driver needed, and the collector-emitter rating of 55V gives headroom for 24V industrial rails.
The -3 CTR bin at 1 mA
The -3 suffix in the order code selects the 100% to 200% current transfer ratio range, measured at 1 mA forward current. That means with 1 mA through the LED, the output transistor can sink at least 1 mA and up to 2 mA at the collector — a tighter, higher-gain bin than the -1 or -2 variants. For a design that drives the LED from a GPIO with limited current capability, or that needs consistent gain across temperature, the -3 bin gives a known floor without overdriving the input. The typical forward voltage is 1.1V at that current, so a 3.3V logic rail can drive it through a series resistor with margin.
The 3.5 µs rise and 5 µs fall times, plus 6 µs turn-on and 5.5 µs turn-off, suit 10-50 kHz switching applications like isolated gate drives or low-speed serial isolation. For faster data rates (MHz-range), a logic-output optocoupler would be the better fit.
Package, mounting, and compliance
Supplied in a 4-SMD Gull Wing package (Tube shipment), surface-mount compatible with standard reflow profiles. The gull-wing leads give a visible solder joint for inspection — useful in high-reliability assembly. ROHS3 compliant per the listing, with no exemption issues. Active lifecycle status from Vishay means no end-of-life notice to track; this part remains a current catalog item.