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tlk110: PU/PD resistor on pin COL and RX_DV

Shu-Cheng LIN
Guru 11785 points
Part Number: TLK110

Hi Sirs,

We need confirm one thing on TLK110

Why do i need to add external PU/PD resistor at strap pin COL and RX_DV?

Because we saw datasheet show there had internal PU/PD resistor, but EVM add external PU/PD resistor

Before,we had issue because we didn't add these resistor, already fix after add external PU/PD resistor.


Could you explain why we need add external PU/PD resistor on these pins?

  • 0
    TI__Mastermind 26135 points
    Hello,

    Thank you for using the TI forum, we will get back to you as soon as we can.
  • 0
    TI__Mastermind 18425 points
    Hi Shu-Cheng,

    The internal resistors in the PHY are weak, in the order of multiple kohms. If the pin is left floating, these internal resistors help the device to be strapped in one known default value. They are delibrately kept weak so that customers can easily strap the device in any non-default mode that they need.
    The pins highlighted in your questions are sometimes routed to the MAC. The MAC may have its own internal pull resistors or it may drive a unknown voltage on these pins during start-up. This might cause the PHY to be strapped in incorrect mode. In these cases, adding external pull resistors is required.

    -Regards,
    Aniruddha