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DS90C365A: Output differential signal, break one, show the problem

jh chen
Prodigy 100 points
Part Number: DS90C365A
Other Parts Discussed in Thread: AM3352

Use the LCD interface of AM3352 to connect the DS90C365A, and then connect the LCD screen.

Either TxOUT2+ or TxCLKOUT + is broken due to the problem of the interface cable. And the corresponding output differential signal will have problems

The external display is normal.

However, when switching to a specific interface, the display will appear flower screen, switch back to the display is normal.

By monitoring the output signals of TxOUT2+, it is found that when switching to a specific interface, the signal voltage decreases. This may be the cause of LCD receiver recognition.

TxOUT2+ or TxCLKOUT + these two line ，arbitrary break a signal line, why display can be normal? Also, why does a flower screen appear for a particular interface or color?

Thank you very much!

  • 0
    TI__Guru** 100955 points

    Jh,

    I am having difficulty understanding your question here. Are there any pictures or diagrams you can add to help clarify the question? 

    In particular I do not know what this sentence means: 

    jh chen said:
    By monitoring the output signals of TxOUT2+, it is found that when switching to a specific interface, the signal voltage decreases. This may be the cause of LCD receiver recognition.

    Also what is flower screen?

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 100 points

    • Sorry, it's a translation problem.　　 TxCLKOUT+ is broken。 TxCLKOUT- is normal connection。The LCD can be displayed properly。

      However, when switching to another graph, the display is abnormal。

    “flower screen”　－－－－》　　The LCD display slowly turns white from edge to center。

  • 0 in reply to jh chen
    TI__Guru** 100955 points

    jh,

    Honestly there is very little to go on in this explanation. If the TxCLKOUT+ is not connected currently it is very difficult for us to explain what the behavior will be. I suppose it may depend on how much signal swing is left from the still connected TxCLKOUT- portion of the differential signal. Perhaps with one video format the clock rate is slower which provides slightly higher signal swing so that the display can still come up correctly, but with another video format the clock rate is higher so the signal amplitude goes down slightly and causes this problem?

    Best Regards,

    Casey