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TMDS1204: HPD being driven high

Irfan Shaikh
Intellectual 300 points
Part Number: TMDS1204
Other Parts Discussed in Thread: TXS0104E

Tool/software:

Dear Team,

I am using TMDS1204 re driver IC in which HPD for TX is connected from connector to level translator and then to the Re-driver IC.
The issue i am facing is when i turn on the board the level translator is pulling up the HPD without turning on the board and the Re-driver IC is getting Logic 1 and and output of it connected to the FPGA through the circuit as attached in the schematics.
Since the toggling should happen only when cable connected but it doesn't happen as per our logic .
Our logic was initially high and then low so we have kept Active low in FPGA Design.

Could you please suggest why it is happening without connecting the cable , why the HPD is pulled.

Regards,
Irfan

prjcl-hdmi.pdf

  • 0
    TI__Mastermind 24010 points

    Hello Irfan,

    The most likely scenario is the TXS0104E is pulling the HPD by its integrated pull-up resistor. 

    You can force the I/Os into a Hi-Z state by toggling the OE pin low.

    Regards,

    Josh

  • 0 in reply to Joshua Salinas
    Intellectual 300 points

    Dear Joshua,

    I can't toggle the OE pin as it being pulled to VccA.
    Can you please recommend any other solution.
    Also in our previous project we did use this level translator for HPD signal and i have also attached it for your reference, can you please tell why it didnt behave like now?

    Regards,
    Irfan
     

  • 0 in reply to Irfan Shaikh
    TI__Mastermind 24010 points

    Hello Irfan,

    When comparing the current and previous TXS projects, are we doing an apples-to-apples comparison? Test conditions and supply voltages being apply the same? 

    You can force the I/Os into Hi-Z by toggling OE low or having either supply at 0V. 

    Regards,

    Josh