I am using a Common Anode RGB LED in my project(datasheet is given below) and the different specifications for each LEDs are giving me headache. In my schematics, as shown below, I have used individual current limiting resistors valued at 150ohm. The common anode is tied to the 3.3V source. The LEDs are driven by an NPN and the switching is controlled by an MCU. enter image description here

  • The RED and BLUE LED have max VF=2.4V and 3.15V, which is smaller than the source 3.3V

I have a feeling that something is off in my schematic design. enter image description here

  • \$\begingroup\$ And what is your question? \$\endgroup\$ Commented Feb 20, 2020 at 7:59
  • \$\begingroup\$ @RohatKılıç I am using 150ohm current limiting resistor. Is this value right? I have noticed that the green LED lights up the brightest and the Blue LED stopped working after few hours. \$\endgroup\$
    – adnan
    Commented Feb 20, 2020 at 8:01

1 Answer 1

  • The net names and the LED pins doesn't match. (Green and blue nets are interchanged).
  • The maximum current through the LED can be 6 mA at 2.4 V Vf. This would be about 6 mA.
  • The forward Voltage for green LED (NG) is about 3.3 to 3.9 which would make it impossible to lit with a 3.3 V source.
    enter image description here

  • Change the 3.3 V source to 5 V or higher depending on other voltages you have on th board


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