The PS2565L-1-V-F3-A is a single-channel phototransistor optocoupler from Renesas's NEPOC series, built to pass 5000Vrms across the isolation barrier. That rating is the main event: it lets you separate a high-voltage primary side from a low-voltage control circuit in a single surface-mount package, the 4-SMD gull wing. The transistor output can switch up to 80V across the collector-emitter and sink 50mA per channel, which covers most PLC digital inputs, relay drivers, and isolated feedback paths in AC-DC supplies.
CTR at 5mA — the margin you design to
The current transfer ratio is specified at 5mA forward current: minimum 80%, maximum 400%. The 400% ceiling matters when the phototransistor saturates hard — the Vce saturation is only 300mV max, so the output pulls cleanly to ground even with high CTR. Rise and fall times are 3µs and 5µs typical, fast enough for 10-50 kHz switching but not for high-speed data; this is a power-isolation and low-speed signal part, not a digital isolator.
The ROHS3 compliance is standard for lead-free assembly.