Backlightb LED got dimmed Issue!



  • Paul_B

    Hi RAGHUK,

    The NHD-1.8-128160EF-CTXI#-T does not contain a current limiting resistor, please see page 3 in the displays datasheet for the backlight circuit.

    Unfortunately, it would appear that your TFT is toast  

    Listed below are two options for driving your Backlight:

    • Place current-limiting resistors in series with the LEDs to prevent them from blowing out.
    • Use a constant current LED driver (Schematic Attached).

    Thanks, Paul.
    From your two suggestions, placing a current-limiting resistors in series with the LEDs seems to be the simpler one, as it requires a simple modification in the existing schematic and gerber.
    Since the Backlight Supply Voltage = 3.3 V (Max) and 2.8 V (Min) and Backlight Supply Current = 30 mA (Typ), can we provide a 3.3V through a current limiting resistor to the LEDs? Whether it will cause a voltage drop across the resistor resulting in less voltage (less than 2.8V) to the LEDs?
    Could you pls suggest a resistor value for this case?

    Thank you for your time.
  • Sergio_M

    Hi RAGHUL,

    Using a 10 ohm resistor in series with the LED backlight and a 3.3V source voltage will provide the 30mA at 3.0V to the LEDs.
    Formula: R = (Vs - Vf) / If

    Hope this helps!


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