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DP83849I: RBIAS resistor

user6071654
Prodigy 30 points
Part Number: DP83849I

I would like to know how to fix RBIAS(32pin) resistor value.

Due to datasheet 4-87k ohm resistor must be connected from RBIAS to GND.

However I cannot fix which value resistor is connected.  

Could you let me know calcuration method of RBAIS resistor?

Thank you and best regards

Nonaka

  • 0
    TI__Mastermind 18425 points

    Hi Nonaka,

    You will need to connect a external resistor on the PCB with 4.87kohm 1% tolerance resistance between RBIAS pin and ground. This value is important for proper operation of the PHY.

    -Regards

    Aniruddha 

  • 0 in reply to Aniruddha Khadye
    Prodigy 30 points

    Dear Aniruddha

    Thank you for your quick reply.

    I would like to know more information about this issue.

    I would like to know not only resistor value but also how to calculate about this value.

    And which performance is related this value.

    Could you kindly reply for me.

    Thank you and best regards

    Nonaka

  • 0 in reply to user6071654
    TI__Mastermind 18425 points

    Hi Nonaka,

    There is not calculation required for selecting this resistor. The resistor should be of fixed value, 4.87kohm 1% tolerance. This value was decided as per the design of the device. This resistor sets biasing for the internal blocks of the PHY and it will affect device performance if the datasheet value is not followed. The device performance like IEEE compliance, power consumption, etc can be adversely affected. So I would recommend to use 4.87kohm 1% tolerance resistor as the datasheet requires.

    -Regards

    Aniruddha