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Original question:

DS90CP02: schematic review

DS90CP02: DS90CP02: Noise issue

Amit Gupta
Prodigy 10 points
Part Number: DS90CP02
Other Parts Discussed in Thread: DS90CF386

Tool/software:

Dear All,

we are using DS90CP02 as splitter for LVDS signal. See attached block diagram for our system. 

Please look into below observations & help to resolve the noisy lines issue:

1. Once we connect AMOLED Display along with HDMI Display, there are three Noisy Lines in HDMI Display.

2. If we do not connect AMOLED Display, there are no Noisy Lines in HDMI display.

I am attaching a block diagram for your reference. Please let us know if any further details are required.

   Noisy lines issue.pdf

  • 0
    TI__Guru* 93670 points

    Hi Amit,

    Interesting problem you have here!. Questions:

    1). Are of these TI devices on the same PCB or board? Do they share supply and GNDs?

    2). What happens if you connect supply and control signals for AMOLED but not DSI signals(4 lanes + clk lane)?

    3). Similar to #2 above but do not connect supply and control but connect DSI signals?

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Intellectual 450 points

    Hi Nasir,

    Please see below response:

    1.Yes, these devices are on same PCB. Thet do share same power supply and GND.

    2. We have not tried that because control + power + DSI signal share same FPC connector.

    3. Same as above.

    In first revision, we thought that there is some noise coming from AMOLED on DSI which get coupled from DS90CP02SP splitter then to DS90CF386 and then to HDMI IC FP410PA. In second revision, We also tried with Isolator ADN4620BRSZ on AMOLED DSI Lines but the problem remains same.

    What do you suspect here, Is it something related to EDID or is it some noise coupling or something else.

    For point 2, 3 we will try to implement & share the results.

    regards

    Vinod Sharma

  • 0 in reply to vinod sharma
    TI__Guru* 93670 points

    Hi Vinod,

    I am thinking it could potentially be a noise coupling issue. Two experiments mentioned above could tell us where it could be coming from. Based on two experiments, noise or bit error could get worse but we should run this experiment and observe the result. Hopefully this would tell us the root cause.

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 160 points

    Hi Nasser,

    We are facing difficulty in doing mentioned experiments because

    1. Some software dependency as few safety features are implemented from controller end

    2. The signal lines & control lines share same connector, but some tests we have performed below

    S.No.              Tests Single AMOLED connected Single HDMI Connected Both AMOLED+HDMI connected
    1 When Control & Power lines are disconnected Blank screen Blank screen Blank screen on both
    2 When power lines are disconnected Blank screen Blank screen Blank screen on both
    3 When DSI signal was disconnected Blank screen Video is coming (without flickering) Blank screen on both

    Is there any other way of doing this??

  • 0 in reply to Jitendra kumar
    TI__Guru* 93670 points

    Hi Jitendra,

    How about if your don't turn power on AMOLED display but have LVDS-1 signals active or disconnect LVDS-1 while signal is running? Do get video flicker on TMDS signals?

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 160 points

    Hi Nasser,

    We have tested same thing , also shared same test in table S.No 2, if AMOLED power is turn off then both display has  no any video. Please share you mail id for that we can resolve this issue in less time.

    Regards,

    Jitendra

  • 0 in reply to Jitendra kumar
    TI__Guru* 93670 points

    Hi Jitendra,

    You can send me friend invite and we can have private discussion about this.

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 45 points

    Hi Nasser,

    Thank you for your response. Now Jitendra is not working on this activity. I will work on this further and I have shared you the friend invite. Please accept and we can do private discussion further on this topic.

    Thank you in advance.

  • 0 in reply to Ginni viyogi
    TI__Guru* 93670 points

    Sounds good.

    Regards, Nasser