5000Vrms isolation in a 4-SMD gull-wing package
The Renesas NEPOC PS2561DL2-1Y-F3-A is a single-channel transistor-output optocoupler designed for galvanic isolation in industrial and power-conversion interfaces. Its 5000Vrms isolation rating suits reinforced insulation requirements for mains-voltage separation in PLC digital inputs, motor-drive feedback, and AC-line monitoring circuits. The 4-SMD gull-wing package supports automated surface-mount assembly and visual inspection of solder joints. Key parametrics include a current transfer ratio (CTR) range of 50% to 400% at 5mA forward current, a maximum Vce saturation of 300mV, and an output transistor rated to 80V and 50mA continuous. Rise and fall times are 3µs and 5µs typical, limiting the practical switching rate to low-speed digital signals such as 50/60 Hz line sync, relay coil feedback, or slow PLC input sampling. The 1.2V typical forward voltage and 40mA maximum forward current are standard for 3.3V or 5V logic-driven LEDs with a series resistor.
For dual-sourcing resilience, the PS2801C-4-V-A is a four-channel variant with 2500Vrms isolation and similar transistor-output characteristics, though it is not a pin-compatible drop-in due to channel count and package differences.
CTR range and drive margin for the BOM
The 50% minimum CTR at 5mA forward current means the output transistor can sink at least half the LED current, which directly sets the pull-up resistor value on the output side. A 5mA LED drive with a 10kΩ pull-up to 5V yields about 0.5mA base drive — enough to saturate the output below 300mV for a logic-low signal. The 400% maximum CTR gives headroom for LED aging or temperature derating; designs should verify the minimum CTR at the lowest expected operating temperature and LED current. At 3.3V logic, the 1.2V Vf leaves about 2.1V across the current-limiting resistor. A 390Ω resistor sets the forward current near 5mA, keeping the LED within the 40mA absolute maximum and maintaining the CTR within the specified test condition. The 80V output rating allows direct interface to 24V industrial logic or 48V telecom rails without an external level shifter.