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My add-in card uses a pair of pins to drive an external activity LED, with anode "provid[ing] 220 ohm pull-up to +3.3 V".
However, the LED that I wish to drive with these pins, is designed to be driven by "LED pull-up to +5 V".

How do I proceed?

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  • \$\begingroup\$ Does this LED you are trying to use have a built-in resistor? A link to its datasheet would be helpful. \$\endgroup\$ – evildemonic Sep 24 '20 at 18:49
  • \$\begingroup\$ How do I proceed - get an appropriate LED \$\endgroup\$ – Eugene Sh. Sep 24 '20 at 18:57
  • \$\begingroup\$ Eugene: no can do. The LED in question is molded. \$\endgroup\$ – Kostya Sep 25 '20 at 13:03
  • \$\begingroup\$ evildemonic: I, too, wish I knew more about the part. But it is barely accessible and has no visible markings on it. I can only assume it is indeed a 5V part since that would fit the Intel ATX spec for ATX chassis LEDs. \$\endgroup\$ – Kostya Sep 25 '20 at 13:05
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What they're saying is the '5V LED' has internal resistor. Your card also has a resistor (220 ohms). So what will happen is that the LED will be very dim since it will be running on 3.3V -> 220 ohm -> LED dropping resistor in series.

If you can modify the LED to short out the resistor it could work, or replace it with a plain (non-resistor) LED.

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