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DP83822I: MDIO and RBIAS Pull-up/down Resistor Value Range

Cyrus Kelly
Prodigy 240 points
Part Number: DP83822I
Other Parts Discussed in Thread: DP83TD510E

Hello,

I am connecting a DP83822IRHBR to a DP83TD510E back-to-back via the RMII interface. 

The DP83822IRHBR datasheet says RBIAS requires a 4.87K to GND.  How much flexibility is there in the resistor value?  Can I use a 4.3K, 4.7K, 5.1K?

The DP83822IRHBR datasheet says the MDIO pin requires a 2.2K pull-up resistor.  How much flexibility is there in the resistor value?  Can I use a 3.0K, 2.7K, 2.49K, 1.8K?

Thanks,

Cyrus

  • 0
    TI__Mastermind 39785 points

    Hi Cyrus,

    For R_Bias, a 4.87kOhm 1% tolerant resistor must be used. For MDIO, a 2.2kOhm 1% tolerant resistor must be used.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 240 points

    Hello Gerome,

    I am connecting a DP83822IRHBR to a DP83TD510E.  The DP83TD510E datasheet says the MDIO pin, "requires an external pull of 2.2kΩ - 4.0 kΩ."  Can you please double check that this is not the case for the DP83822IRHBR MDIO pin?  I'm trying to keep my part count down.  Being able to use a 4.7K for the R_Bias pin would be helpful too.

    Thanks,

    Cyrus

  • 0 in reply to Cyrus Kelly
    TI__Mastermind 39785 points

    Hi Cyrus,

    R_Bias needs to be the intended value per datasheet. It is highly advised to not deviate against it as it may cause the PHY to not work properly.

    If part count is important to you regarding MDIO, both PHYs support a 2.2k pullup for MDIO so you can use that single component for the entire node.

    Sincerely,
    Gerome