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DP83822IF: Ethernet PHY 10/100 Mbps RMII uP MAC Interface, with both Hardware Magnetics/RJ45 + FIBER

Michele Bonollo
Prodigy 200 points
Part Number: DP83822IF
Other Parts Discussed in Thread: DP83822HF,

Tool/software:

Hi,

I'm search for a New PHY Chip with minimum RMII interfaces and 10/100Mbs speed, small package, Low pin count <= 32pin 

I see your DP83822  may be the best choose ??

Another important discriminating factor for the choice is the fact of having both copper output with magnetic/RJ45 and optical fiber with capacitive decoupling as for the DP83822.

Question:  for the DP83822IF or DP83822HF model is possible to have via Hardware  simultaneously both the coupling with magnetic RJ45 and fiber optic module ??? same hardware with pins shared in parallel and appropriately decoupled??? Obviously; via firmware you can only use one or the other transmission method at a time! 

Thank you

  • 0
    TI__Mastermind 32325 points

    Hi Michele,

    The DP83822 can work for this application. This PHY will work with both copper and fiber optic interfaces as shown in the block diagram below. 

    Michele Bonollo said:
    is possible to have via Hardware  simultaneously both the coupling with magnetic RJ45 and fiber optic module ???

    I do not recommend having both fiber and copper interfaces connected in parallel. This would split the signal path and create a large stub in your PCB trace. Since high speed signals are sensitive to trace routing, it would hurt your signal performance to do this. I recommend using either fiber or copper as the interface on the MDI side of the PHY, not both.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 200 points

    Thanks  @Shane Hauser for the analysis, yes you are certainly right, I feared and intuited this, being the 100Mbit/s rate with frequency bands of 25Mhz or 50Mhz.

    Sorry for the last few questions:

    1) OK i don't connect both the path fixed in parallel; but if I want both interfaces on the board:
    I will create two separate paths, as short as possible adapted in impedance, then I will configure the connection with jumpers or 0 Ohms,
    for Pin 9-10-11-12 that are shared, I have only RMII interface in the uP parts.
    The pin 24 SD_IN may be only for the fiber ??. And for the 25-MHz / 50-MHz Clock Source I foresee all the configurations.

    is everything correct??

    2) At the current state of things, the most innovative and convenient PHY TI chip to have RMII, 100Mbit, with few pins is this DP8322
    or would you have others models to suggest/evaluate ?? If i don't use the Fiber all four che chip are pin ti pin compatible?? (HF/H/IF/I)

    Thank you

  • +1 in reply to Michele Bonollo
    TI__Mastermind 32325 points

    Hi Michele,

    Michele Bonollo said:
    then I will configure the connection with jumpers or 0 Ohms

    If you plan to do this I recommend using 0-ohm resistors rather than jumpers. Headers with jumpers will act as antennae when you route a high speed signal through them. This can create an unnecessary source of EMI emissions.

    Michele Bonollo said:
    The pin 24 SD_IN may be only for the fiber ??

    Yes SD_IN is an alternate function for LED_1 that is only used in fiber mode. This should connect to the optical transceivers signal detect signal as described in the datasheet:

    Michele Bonollo said:
    or would you have others models to suggest/evaluate ?

    The DP83822 is the best option for this application. It's the only 10/100Mbps PHY we have that supports a fiber interface:

    For another PHY that supports fiber you'd need to look at our 1000Mbps portfolio.

    Michele Bonollo said:
    If i don't use the Fiber all four che chip are pin ti pin compatible?? (HF/H/IF/I)

    Yes that is correct. The 'H' variants are extended temperature versions of the base 'I' variants. Both have the same pinout.

    Best,

    Shane