3750Vrms isolation in a 4-SOIC footprint
The Toshiba TLP291(GRL-TP,SE is a single-channel DC-input transistor-output optocoupler rated for 3750Vrms isolation, packaged in a 4-SOIC (0.179", 4.55mm width) surface-mount case. It is designed for galvanic isolation in industrial control, power supply feedback, and digital interface applications where the board space is tight but the safety rating is non-negotiable.
CTR binning — the GRL rank at 5mA
The GRL suffix selects a current transfer ratio (CTR) window of 100% to 200%, measured at 5mA forward current. That middle band gives the designer a predictable LED drive current: at 5mA input, the output transistor can sink between 5mA and 10mA (CTR × If). This matters when you are sizing the input-side resistor for a given logic-level threshold or relay coil current. The 100% minimum ensures the opto turns on reliably even with a weak LED drive; the 200% cap prevents saturation delay from getting too long in high-speed switching.
80V output and 50mA per channel
The output transistor is rated for 80V collector-emitter voltage and 50mA continuous output current. That voltage headroom covers 24V and 48V industrial buses with margin; the 50mA limit is typical for driving a logic gate input, a small relay, or a PLC input module.
Rise and fall times are 2µs and 3µs typical; turn-on and turn-off times are both 3µs typical. That puts the usable switching frequency around 100 kHz or lower for clean pulse transmission. If you need faster edges for a high-speed serial isolator, this is not the part — but for 50/60 Hz mains zero-cross detection, relay drive, or slow digital isolation, the timing is more than adequate.
The 110°C ceiling is below automotive under-hood requirements (typically 125°C or 150°C), but it covers the vast majority of factory automation and power-supply applications.