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TMDS251

Newton
Expert 1125 points
Other Parts Discussed in Thread: TMDS251, TMDS442

Need to make a 2-to-1 DVI switch -- but  need a Dual Link DVI configuration. The TMDS251 only has 4 TMDS channels and we need five. Can we use a second TMDS251 to pick up TMDS channel 5 and if so what is the best way to arrange/connect the two devices? Is there any recommended layout information.

  • 0
    TI__Genius 16440 points

    Please see this thread which I believe addresses your question.

  • 0 in reply to DHarmon
    Expert 1125 points

    Thanks for this.

    Is there any detailed schematic or ref circuit or design for "typical application" shown on page 31-32 of the Data Sheet for this part.

     

    regards

  • 0 in reply to Newton
    TI__Expert 6745 points

    I have a TMDS442 EVM schematic attached.6237.tmds442evm_schematics.pdf

  • 0 in reply to Ken Shaw
    Expert 1125 points

    Ken,

    Thank you so much.

     

    regards

  • 0 in reply to Ken Shaw
    Expert 1125 points

    I have questions on the schematic for HDMI refrence design that was sent to me:

     

    The design is a  2 to 1 Dual DVI device for  Displays:  

    On the reference design, the I2C pull-up resistors have a note indicating that they need to be changed to 47k on some and 5.9k on others. Were these notes added to show what needs to be changed for the DVI vs HDMI usage?  The Data Sheet also talks about  computing/selecting these resistor values.   Is there a common value that is typically used for DVI? Along the same lines, the pull-up is noted as being 3.3V or 5V – the reference design doesn’t specify the value of I2C_Term.  Is there a predominant value that used or should the design be made flexible (which complicates the layout)?

  • 0 in reply to Newton
    TI__Expert 6745 points

    Per the HDMI or DVI spec, pullup resistors for sources and sinks (seen below).  The sink input of the TMDS442 will definitely need to be in the 47k range, otherwise the source will have difficulty driving a low to meet the input voltage requirements (~2k at the source in parallel with the resistor here ).  The TMDS442 DDC source interface connected to the sink, will need a higher resistance than the spec to allow for the offset voltage between the source and sink.  Ideally the sink interface is connected directly to a scalar/receiver and not an external interface.