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TDA4VH-Q1: PRSNT default level?

Tony Tang
Mastermind 27211 points
Part Number: TDA4VH-Q1

Tool/software:

on TDA4VH-EVM schematic page 70, the PCIe0_4L_PRSNT is neither pulled up nor pulled down.

But on AM69-SK Schematic, it is pulled up.

Is there a rule for this signal's default status? 

  • 0
    TI__Mastermind 36022 points

    Hi Tony,

    Based on the electromechanical specifications for PCIe, PRSNT pins needs to be pulled up. For reference, here is a screenshot from the specification documentation:

    TDA4VH-EVM connects the PRSNT signals to an IO expander that can set these as pull-up/pull-down:

    And in comparison, AM69-SK does not connect to the IO expander as shown in below screenshot with "DNI" (Do Not Install) for the resistors to connect PRSNT signals to expander, since the pins on the expander are used for something else:

    Therefore, AM69-SK board requires an external pull-up resistor to comply with the specification.

    Regards,

    Takuma