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DS90UB921-Q1: DS90UB921 can not connect ds90ub948 deserializer

xiaotang
Prodigy 115 points
Part Number: DS90UB921-Q1
Other Parts Discussed in Thread: DS90UB948-Q1

 we used DS90UB921-Q1and ds90ub948-q1 as RGB video output , now there are RGB signal on DS90UB921-Q data nad clock input pin ,but  there are not any signal on the ds90ub948-q1 deserializer ,besides,We already setted I2C pass-through at 0x03 register , as a result , there is not  ds90ub94 device address on the I2C bus , what reason do cause ?the attched file is Sch circuit: plaese review and check our circuit , i am afraid circuit problem , I have two problem: 1: DO DS90UB921-Q1 need external crystal? 2: Does  DS90UB921-Q1 output Pina  connected correctly ds90ub948-q1 input pin?

948.pdf

  • 0 in reply to xiaotang
    TI__Mastermind 30515 points

    Hi,

    Since the 921 is linked with 948 through cable/connector etc., you should check step by step which is wrong here. some commetns:

    1. 921's working freq.: FSEL setting is correct or not based on 921 d/s notes on FSEL pin and your system application condidtion

    2. check the common mode choke F20000 is selected correctly or not since the channel has ~Mbps ~~ Gbps signals transmitted 

    3. check connector pinout of the 948's board, are they matched? from your 921 board, the HSD input indicates pin1/3 are channel0, this is aligned with TI's EVM board pinout, you can use TI's 948 EVM for link (if you have no TI EVM board, you can buy TI 948-HDMI bridge board which is produced by TI's 3rd party company though wechat number: Baizhun_Tech) for test.

    regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 115 points

    Hi Steven:

         Thank youvery much  for your reponse ,about  second  and third  suggestions you mentioned,  I  do not understand your means ,could you descripte detailly? Besides  I found one problem, our circuit is differential output of ds921, but i measured waveform with  oscilloscope, it shows single-ended VOUTDC Output of serializer. What causes this phenomenon？ i do not know  how to solve it,  I have seek help to TI FAE , He suggested me to search similar issue on E2E forums

  • 0 in reply to xiaotang
    TI__Mastermind 30515 points

    hi, pls check below:

    for 2nd issue, pls check your sch., the component F20000 is used here, what is the spec.?

    for 3rd issue, since the conector has 4pins, pls check if they are mapped correclty?

    regards,

    Steven