What this optocoupler does in your circuit
The TLP291(GRH,SE is a single-channel transistor-output optocoupler from Toshiba, designed for DC input and rated for 3750Vrms isolation between input and output. It delivers a current transfer ratio between 150% and 300% at a forward current of 5 mA. The output transistor is rated for 80 V maximum and 50 mA continuous current.
Rise and fall times are 2 µs and 3 µs typical, with turn-on and turn-off both at 3 µs.
Package and mounting for the assembly line
Housed in a 4-SOIC package with 0.179-inch (4.55 mm) body width. The supplier device package is 4-SO. Check the MSL rating before reflow — Toshiba optocouplers in this family typically carry MSL 1, but verify the reel date code to avoid popcorning.