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TPS61161: Resistance value between the FB pin and GND

Dice-K
Mastermind 6330 points
Part Number: TPS61161


Hi support team,

After using TPS61161 for half a year, the LED started blinking.
The resistance value between the FB pin and GND is 11.6Ω.
Is TPS61161 damaged and short-circuited?

Please let me know if there is such a precedent.

Regards,
Dice-K

  • 0
    TI__Genius 13001 points

    Hi Dice,

    Could you please provide SW, Vout, Iout scope shots for analysis?

    In addition, please also make sure that the related capacitors are all OK, especially for Cout.

    BR,

    Robin

  • 0 in reply to Yuting Shao
    Mastermind 6330 points

    Hi Robin,
    Thank you for your reply.

    I got the VIN and VOUT waveforms. VIN and VOUT are unstable.
    I want to send waveform data as a private message.

    The load LCD is a separate board.
    The LCD board was inserted and removed many times.

    Is it possible that repeated insertion and removal damaged the ESD cell of the FB terminal and caused a short circuit failure?

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    TI__Genius 13001 points

    Hi Dice,

    I'll request friendship from you and you can send me these plots.

    According to your description--blinking, it seems not a shot circuit issue.

    BR,

    Robin

  • 0 in reply to Yuting Shao
    Genius 3865 points

    Hello Robin,

     

    This is Mochizuki worked together with Dice.

    He is going to send you the customers measurement data.

     

    Here is some background information, we have heard from the customer.

    1. They set 4.7mA output current by using Rset 27ohms. Vout was around 8V and initially it works well.

    2. During ES sample evaluation, they plug in-out this LED driver board to LCD backlight module.

    3. After while 2units made strange LED brightness.

    4. They try to measure FB pin resistance as Dice mentioned before. They apply 2.5V high impedance resistance meter.

      The result shows some leakage current at FB pin of damaged TPS61161.

    5. Our expectation is that TPS61161 internal ESD cell was damaged by EOS or ESD during hot plug in-out. There is no order GND and Vdd connection at LDC module Flat cable.

    6. And finally ESD cell create large leakage current, then FB circuit function is changed ,LED current is changed from original setting.

     

    The customer agreed if this story is right expectation they will add over voltage protection device to FB pin.

    Do you see this story is possible root cause?

     

    Of cause we can go FA to get evidence, apply pin to pin I-V characteristics and if needed apply de-cap package to see ESD cell damage directly.

    However it will take time and cost, before fix their mass production product schematics.

     

    Regards,

    Mochizuki

  • 0 in reply to Mochi
    Genius 3865 points

    Hi Robin,

     

    I not sure your time zoon but can we have a reply or direct contact mail address today?

     

    Regards,

    Mochizuki

  • 0 in reply to Mochi
    TI__Genius 13001 points

    Hi Mochi,

    Since this issue is a little strange, I will give Dice my email address and you can send me the detailed description. I'll loop in my colleagues to have a further analysis. 

    Thanks!

    BR,

    Robin