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DP83822IF: Interface to Avago AFBR-5972Z

Gregg Norris
Prodigy 10 points
Part Number: DP83822IF

Hello,

I would like to use the DP83822IF with the Avago AFBR-5972Z. 

I see Avago has a note showing how to connect a Micrel KSZ8041FTL: https://www.farnell.com/datasheets/1870313.pdf  page 5

It's looks very different than the diagram in the data sheet for the DP83822IF.

Can you please help?

Thanks,

Gregg Norris

Applied Materials

  • 0
    TI__Mastermind 19250 points

    Hello Gregg,

    I see that there is a difference in the circuit connected closer to the Avago Fiber transceiver. My guess is that the circuit on TX+, TX- are for defining common mode voltage for the transceiver. I am not sure about the receive side circuit.

    Anyways, the circuit on the KSZ8041 side is same as that required for DP83822. On the AFBR5972 side, you'll have to check with Avago, to understand the requirement.

    --
    Regards,
    Gokul.

  • 0 in reply to Gokul Koraganji
    Prodigy 10 points

    Hello Gokul,

    If your goal is to help me so TI can sell more chips, then it'd be great if you could find out the answer and let me know. 

    Thanks,

    Gregg

  • 0 in reply to Gregg Norris
    TI__Mastermind 19250 points

    Hello Gregg,

    I'll definitely help if I could. However, the circuit on the Optical side depends very much on the internal implementation of optical transceiver.

    It is very difficult to guess the internal implementation just from the datasheet of these optical transceivers.

    So, only the folks who know internal design implementation of the optical transceiver can comment on that circuit.

    --
    Regards,
    Gokul.

  • 0 in reply to Gregg Norris
    Prodigy 10 points

    Hello Gokul, 

    Can you help me here?

    Thanks,

    Gregg

  • 0 in reply to Gregg Norris
    TI__Mastermind 19250 points

    Hello Gregg,

    I am sorry, but I can't base the circuit implementation on AFBR5972 side based on my guess on their internal implementation. It could lead to incorrect conclusions on my side and wrong implementation.

    On the DP83822 side, you can use the same implementation as that on KSZ8041 side.

    --
    Regards,
    Gokul. 

  • 0 in reply to Gregg Norris
    Prodigy 10 points

    Page 6 of the document at the following link describes the internal configuration of the AFBR-5972Z

    https://www.farnell.com/datasheets/1870313.pdf

    Does this help you figure out how the DP83822IF should best be connected to the AFBR-5972Z?

    Thanks,

    Gregg

  • 0 in reply to Gregg Norris
    TI__Mastermind 19250 points

    Hello Gregg,

    On the TX+, TX- of AFBR5972, there are pull up and pull down resistances of 10kohms. I understand that they are to set common mode voltage of TX+ and TX- pins.
    I am not sure what happens if we don't mount those resistances. Are they always required or are they required only for compatibility with KSZ8041 and IP101G? Only folks from Avago can answer that.

    On RX+, RX- pins, pull down resistances of 150ohms are very peculiar to me. Does this mean there are some resistances inside AFBR5972 which equivalently make effective impedance on each pin 50 ohm?

    There are lot of variables on AFBR5972 that I am not aware and I can't suggest or sign-off circuitry on AFBR5972 side. Hence, I was pushing back to get in touch with folks at Avago.

    --
    Regards,
    Gokul.