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TDP142: HD3SS214 and TPS61196, one of the 27 Inches 4K eDP panel did't work perfectly

ZHUOXUAN ZHUANG
Prodigy 90 points
Part Number: TDP142
Other Parts Discussed in Thread: SN65DSI86, , HD3SS214, TPS61196

I am a research student from Hong Kong, I have designed a embedded board to connect my display card to eDP panel cause of my limited budget so i decide to assembly my own display screen base on Ti chips.

besides is my system layout:

My prototype supports HDMI and DP input as the schematic show above, HDMI flow is input to Toshiba TC358870XBG (HDMI to MIPI) then input to Ti SN65DSI86 (MIPI to eDP) then input to channel A of Ti HD3SS214. DP input is connect to channel B of Ti HD3SS214, finally the switched DP signal is connected to TDP142 cause i want to snoop the power state of GPU video signal and use a STM32 to control the panel back light. I have finish my two prototypes, at the beginning, the display work perfectly. The pictures shown below is my display prototype:

My problem is that one of my display can't boot up properly base on the same program flash into the stm32 as two picture shown below

the display which can't work properly, As you can see the left side area is dark it seems that one  of the DP lane signal is weak?

the display work and boot up properly

the backlight LED of two panel is in good condition cause the Ti TPS61196 LED driver can't work if the LED string is in bad conditions, So I am wandering which case can make the display can't work perfectly, I am not the specialist of DP or other video signal embedded design so can anyone help me to solve this problem.

Note: both of the panels is in good condition.

backlight is also good 

Thank you very much 

   

  • 0
    TI__Guru*** 139405 points
    Zhuoxuan

    This does not look like a DP signal issue as you can still see the pixel in the darken portion of the monitor. It looks like a backlight issue.

    Can you please share your schematic? How does the monitor being connected to your board? Is it through a flat ribbon cable? If so, have you replaced and checked the ribbon cable itself.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Prodigy 90 points

    Dear David,

    Thank you for your comments. 

    I am figure out what is going on with this issue when I am writing this reply. Thank you for your comments very much!

    You are right, the DP signal is good, and the panel is connected by standard 0.5mm pitch 30 Pin eDP socket with flat ribbon cable and micro coaxial cable to my board.

    It was cause by the PWM dimming signal. TPS61196 has six separated channel for the LED back light.  

    This issue can be solved after I reset my STM32, so the problem must be one of the PWM signal output is under 20% duty cycle cause i use Timer 1 to generate 4 channel PWM signal. This is proved that I use different back light connect cable the dark position is in the nearby LED string position.

    So I will check the signal when this problems remained.    

    Backlight driver schematic

  • 0 in reply to ZHUOXUAN ZHUANG
    TI__Mastermind 19720 points
    David is out for the week and will get back to you as soon as he gets back.
  • 0 in reply to Michael.Walker
    Prodigy 90 points

    Dear David,

    The problem is that one FBx channel of the TPS61196  was down so I switch the rest channel to the connection point by fly wire, at the beginning, back light work perfectly. After a few days, the whole TPS61196 was totally down. So I am wandering is this cause by the unstable product quality from the chip manufacturing process?

    Thank you. 

  • 0 in reply to ZHUOXUAN ZHUANG
    TI__Guru*** 139405 points

    ZhuoXuan

    Have you tried to replace TPS61196 and see if the new TPS61196 working? Since the issue is no longer TDP142 and more TPS61196 issue, please submit the question under power management, and then LED drive E2E forum for support, .

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 90 points

    Dear David,

    I have already replaced the TPS61196, and the monitor now working in a good condition.

    I have called for help from TI's hotline, but they said the chip is out of warranty cause it was purchased 3 months ago. So I have purchased another one for replacement for replacement.

    I have test the fault IFB channel by the oscilloscope but I have already delete the result so it is no evidence to prove my guess.

    Thank you.