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DP83822I: DP83822 Magnetics interface

Milos Jesic
Prodigy 50 points
Part Number: DP83822I
Other Parts Discussed in Thread: DP83822EVM, DP83848C, DP83848Q-Q1, DP83849C, DP83848I, DP83849I, DP83848YB, DP83849ID, DP83848M, DP83848T, DP83849IF, DP83620, DP83848H, DP83848J, DP83630, DP83848K, DP83640, DP83848VYB

Tool/software:

Hello,

I'm currently using one board with two DP83822 PHYs that is plugged to the small carrier board with the connector and the Magnetics. 

I want to use multiple of these boards in series (EtherCAT) and I'm wondering if I can remove the Magnetics block between PCB1 & PCB2 and PCB2 & PCB3 ?

Thanks!

Milos

  • 0
    TI__Mastermind 23673 points

    Hi Milos,

    It's possible to operate DP83822 without magnetics/transformer on MDI lines.

    For more details on this, please refer to this application report:

    https://ti.com/lit/an/snla088a/snla088a.pdf

    DP83822EVM also has options for transformer-less operation, for an additional reference.

    Thank you,

    Evan

  • 0 in reply to Evan Mayhew
    Prodigy 50 points

    Hi Evan,

    I have a few questions:

    1. The link you posted seems to be applicable only to:

    DP83848C DP83848Q-Q1
    DP83848I DP83849C
    DP83848YB DP83849I
    DP83848M DP83849ID
    DP83848T DP83849IF
    DP83848H DP83620
    DP83848J DP83630
    DP83848K DP83640
    DP83848VYB

    I don't see DP83822 here, can you confirm that this application note would work for DP83822?

    2. If I understand correctly, I just need to add one capacitor in series (33nF, 100V) and to remove 1.8V from the pin 14 on the PHY side (AVD pin)? Should I leave that pin floating or connect it to GND?

    3. Are the pull up resistors on the PHY side necessary? If yes, what value should I use? Also, what value for the capacitance between PHY's 3V3 and GND should be used?

    Thanks!

    Best,

    Milos

  • 0 in reply to Milos Jesic
    TI__Mastermind 23673 points

    Hi Milos,

    Similar principle in application report applies to DP83822.

    Please refer to DP83822EVM schematics here ("3.2 Analog Front-End Schematic"):

    https://www.ti.com/lit/ug/snlu179/snlu179.pdf

    For transformer-less operation, T2 is DNP'd, and C47 - C50 are populated.

    Pull-up resistors are required on MDI lines (50 ohm).

    Please let me know if the schematic clarifies the required network for this.

    Thank you,

    Evan