5000Vrms isolation — the barrier rating that decides fit
The Toshiba TLP385(D4-BL,E is a single-channel transistor-output optocoupler in a 4-lead 6-SOIC package, designed for galvanic isolation between a DC input and a transistor output. The headline rating is 5000Vrms of isolation voltage, which sets the reinforced insulation barrier for applications like industrial PLC I/O modules, motor-drive feedback, and isolated sensor interfaces. The current transfer ratio (CTR) is specified at 200% minimum and 600% maximum at a forward current of 5mA, giving the designer a predictable current gain for driving the output transistor — wide enough to absorb LED aging and temperature drift without losing logic-level integrity.
A CTR floor of 200% at 5mA means the output transistor can sink at least 10mA when the LED is driven at 5mA, which is more than enough to pull a 5V logic input low through a 470Ω pull-up. The 600% ceiling ensures the part does not saturate too hard, keeping turn-off time predictable. Rise and fall times are 2µs and 3µs typical, and turn-on/turn-off times are both 3µs typical — fast enough for 100 kHz switching or isolated serial data at 115.2 kbps. The 80V output rating and 50mA per-channel output current cover most low-side switching and logic-level translation tasks. The 300mV Vce saturation at the output keeps power dissipation low when driving a relay coil or a small DC load.
Temperature range and deployment context
The 6-SOIC package with 4 leads is a compact surface-mount footprint, saving board area compared to DIP-4 optocouplers while maintaining the same isolation rating. The surface-mount mounting suits automated assembly lines.