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Problem with connection

Andrey Lipov
Prodigy 30 points
Other Parts Discussed in Thread: DS90CR215, DS90CR216, DS90CR216A, SN65LVDS84A

Hello, 

  • 0
    TI__Mastermind 29655 points

    Hi Andrey,

    It is difficult to tell based on just the connection diagram. So far, I do not see anything wrong with the connections you have provided from this connector. Can you please provide some more information?

    Are you using a DS90CR215 as a transmitter on your mini-Tx board, or something else?

    It would also be helpful to have the following information:

    • Schematics, pcb layout
    • Scope shot of the input LVCMOS data before the Tx serializer (if possible)
    • Scope shot of the LVDS inputs to the DS90CR216
    • Scope shot of the input LVCMOS clock before the Tx serializer (if possible)
    • Scope shot of the LVDS clock input to the DS90CR216
    • Scope shot of the DS90CR216 output LVCMOS clock and data to verify data setup/hold time

    Thanks,

    Michael

  • 0 in reply to Andrey Lipov
    TI__Mastermind 29655 points
    Hi Andrey,

    1. Are you able to provide oscilloscope shots with images of the waveform for the LVDS data and clock input to the DS90CR216A?
    2. What speed are you running the clock, and do you have details about the cable you are using?
    3. Do you know whether your endpoint (screen) strobes on the rising or falling edge?

    If either the speed you are running is incompatible or the cables you are using are too lossy, this could cause the screen not to display properly. If you use the DS90CR216A, the endpoint (screen) data must strobe on the rising edge.

    You can output LVDS from LVTTL using one of the LVTTL-to-LVDS transmitters, but be mindful of the strobe edge characteristic for the Tx. Using the SN65LVDS84A should be fine in order to transmit 3 x 7-bit LVDS pairs from LVTTL VGA data if the LVTTL transmitter before the SN65LVDS84A strobes data on the falling clock edge. If the transmitter before the LVDS transmitter strobes on the rising edge, the DS90CR215 is a more appropriate choice. The strobe edges must be compatible.

    It would be very helpful to see a full schematic of the design so we can verify other pin settings. Feel free to send more details offline if necessary, such as full schematic and layout via e-amil: m-lu (at) ti.com.

    Thanks,

    Michael