In the reference design, the RE pin is directly connected to the LED.
But it is well known that what color LEDs can be driven is related to the drive voltage and current.
How do I determine what color LEDs this chip can drive?
User5789665,
The IPx pins and REx pins are connected together through an internal FET as you can see in Figure 14. The SN65HVS881 has a current limit that is set by an external reference resistor. The datasheet specifies this max current as 3.6mA with a 25k ohm reference resistor but you can adjust this value based on your needs.
Thank you,
Adam
User5789665, Adam,
An alternative approach would be to use the ISO1212 : 24V digital input device with built-in isolation. In ISO1212, the LED drive current is provided on the isolated side, so that a higher LED drive current (4mA) can be chosen without increasing the current draw from the 24V inputs.
Rgds,
Anant
