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TPS61165: LED Backlight Driver Failure over Time - No Back Light

Syed Waleed Nazar
Prodigy 30 points
Part Number: TPS61165

Hello,


We have used TPS61165 as backlight driver IC for one of our products, which is in the customer pilot phase. On 20% of the devices, we are seeing that after few days of usage, backlight driver IC stops powering the display LEDs. I have checked the PWM voltage waveform, it is 3.3v, 30Khz on both good and bad units.

Our display spec requirements are 16v, 40 mA.

Below is the schematic:

 I have tried swapping displays, on the same PCB, but the issue didn't go away.

Similarly, when I connect the display from a non-working device to a good board, everything seems to be working normally. Hence I am sure that issues not on the LED strip side.
I have also tried to jump wire from backlight IC to directly on the display flex test points for Anode and Cathode to rule out any connector issues but that didn't help either.

Please suggest how can I quickly identify and address the issue. 


  • 0
    TI__Mastermind 22745 points

    Hi Syed,

         Ok, understand your question, here are commons that may help you find the reason:

        1. Have you tried turn off and turn on again? it can recover or not?

        2. Have you tried to replace this abnormal device to a new good board to check whether this device is ok or not?

        3. Have you found any bad issue of this device? 

        4. how about the working temperature? where there is a risk to cause thermal shutdown?

    Regards

    Sean

  • 0 in reply to Sean Zhou
    Prodigy 30 points

    Hello Sean,

    Please see my response inline below:

     

     1. Have you tried turn off and turn on again? it can recover or not?
      - Yes. It did not recover

        2. Have you tried to replace this abnormal device to a new good board to check whether this device is ok or not?
       - I took the IC out from the bad board and placed it on a good PCB. It seems to be working fine.  What does this mean? Is IC detecting any fault on the bad PCB and shutting down? If yes, how can i validate it?

        3. Have you found any bad issue of this device? 
     - Some of the devices were reported to be dropped by the customer, but not all. I have ohmed out and all connections seem ok. Should i test any particular point? Like comp or fb?

        4. how about the working temperature? where there is a risk to cause thermal shutdown?
    - Working temperature is normal (25 C).

  • 0 in reply to Syed Waleed Nazar
    TI__Mastermind 22745 points

    Hi sir,

        From the second message above, it seems something wrong with the previous board, what you can do is you can solder a good device to the previous board to check whether something is wrong with the board.

    Regards

    Sean

  • 0 in reply to Sean Zhou
    Prodigy 30 points

    Already did that. 

    Placing new IC on the problematic board didn't fix the issue. Also, I am noticing that VIn = Vout.  IC is not providing boost functionality on any of the problematic boards. What are the possible causes for this behavior?   

  • 0 in reply to Syed Waleed Nazar
    TI__Mastermind 22745 points

    so you mean a good device doesn't work on the previous board? so you may need to check the board.