3750Vrms isolation in a 4-SOIC footprint
The TLP291(V4GBTP,SE is a single-channel transistor-output optocoupler from Toshiba, housed in a 4-SOIC (0.179", 4.55 mm width) package. It provides 3750Vrms galvanic isolation between a DC input LED and a phototransistor output, making it suitable for signal isolation in industrial I/O modules, PLC digital inputs, and motor-drive feedback circuits. The 4-SOIC package occupies roughly half the board area of a traditional DIP-4 optocoupler, which matters when you are packing eight isolated channels into a 50 mm-wide terminal block interface.
CTR spread and switching speed
Current transfer ratio spans 100% minimum to 600% maximum at a forward current of 5 mA. That 6:1 spread means the designer must size the output pull-up resistor for the worst-case minimum CTR to guarantee the output saturates at the required load current — a 100% CTR at 5 mA If delivers 5 mA at the collector, which is enough to drive a 1 kΩ pull-up to 5 V but marginal for a 10 kΩ pull-up at 3.3 V. This limits the usable switching frequency to roughly 50–100 kHz for clean pulse transmission — adequate for 10 kHz PWM feedback or 1 MHz serial isolation if you accept some pulse-width distortion.
Active production, RoHS, and sourcing posture
It is RoHS-compliant per the current declaration. For BOM planning, the active status means you can commit the line without a last-time-buy risk.