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LP8860-Q1: LEDs output Chthodes connected together and separate comparing.

Longyou Gan
Prodigy 40 points
Part Number: LP8860-Q1

Hello TI expert,

We are using TI LP8860 backlight chip, in our design we make the Cathnod of the 3x LED strings shorted together in display side as below picture. 

Check the LP8860 datasheet seems connecting the LEDs Cathnod separatly is recommanded. The questions are as below, could you please check and comment?  Thanks a lot. 

   1. What will be the disadvantage  or risks if we connect make LEDs Cathnod shorted together?  

  2. Is it mandatoty to separate the LEDs Cathnod? 

  3. What is the benifit if we separate the each LED string Cathnod ?

  3, Is there any special setting we need take care to mitigate the risk/disadvantage of shorting LEDs Cathnod together?  in our design, it is close to PV build, we don't have time to change the design. And in the previous HW validation test, we didn't find any backlight issues. 

 

  • 0
    TI__Mastermind 23725 points

    Hi, Longyou

    LP8860 has the setup for single channel.

  • 0 in reply to Zhiqian Wu
    Prodigy 40 points

    Hi Zhiqian, 

    Thanks for feedaback, no, it is not single channel use case.  pleaes see the connection as below diagram, LP8860 Out1, Out2, Out3 are used, however the Cathnod of the 3x LED strings shorted together in display side.. 

    The questions are :

       1. What will be the disadvantage or risks if we connect make LEDs Cathnod shorted together and then goes to 3x indipendent LP8860 OUT pins?  

      2. Is it mandatoty to separate the LEDs Cathnod? 

      3. What is the benifit if we separate the each LED string Cathnod ?

      4, Is there any special setting we need take care to mitigate the risk/disadvantage of shorting LEDs Cathnod together?  in our design, it is close to PV build, we don't have time to change the design. And in the previous HW validation test, we didn't find any backlight issues. 

  • 0 in reply to Longyou Gan
    TI__Mastermind 23725 points

    Hi, Longyou

       1. What will be the disadvantage or risks if we connect make LEDs Cathode shorted together and then goes to 3x independent LP8860 OUT pins? 

    The current for each channel will have some difference.

      2. Is it mandatory to separate the LEDs Cathode? 

    It is related that if you can accept a little difference light intensity between each channel, it is also related with the LED panel performance.

      3. What is the benefit if we separate the each LED string Cathode ?

    You can control the LED with high accuracy.

      4, Is there any special setting we need take care to mitigate the risk/disadvantage of shorting LEDs Cathode together?  in our design, it is close to PV build, we don't have time to change the design. And in the previous HW validation test, we didn't find any backlight issues.

    No electrical issue for LED driver.