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Network Connector Routing

Former Member

I like the idea that I can put the network connector on my custom board. But I am concerned about the signal quality.


How to route the signals?(Matched impedance? 100 ohms ?)
How long can the routes be ?
Will it run reliably at 1 Gbit ?



  • 0

    The PicoZed Carrier Card is running 1 Gb/s reliably in the lab now. There is a section in the PicoZed Carrier Card Design Guide, that will be released in the near future, titled "Routing 1Gb/s Ethernet Port Through the PL"  with guidelines that are applicable to the network signals:

     

     

     All Giga-bit signals should be routed stripline using micro-vias between the appropriate layers.

     Use 4x spacing between pairs.

     Single pair (P and N) should be length tuned to within 25 mils of each other (P to N) at 100Ω differential impedance, with no more than two transitions (vias) for these signals.

     All Data, clock and control signals (RX, TX, MDx) should be routed at 50Ω impedance and not exceed the PHY manufacturers’ recommended length requirements.

     All interface signals should be routed to within 250mils of each other.

     

    There is no specific length specification for the routes other than as short a possible. If you are working with an Avnet / Silica FAE you will be able to request the PicoZed Carrier Card PCB files as an example once they are released.

     

    -Gary

  • 0

    Sorry, I don't get it.

    According to schematic, there are 8 critical signals:
    ETH_MD1_P
    ETH_MD1_N
    .
    .
    ETH_MD4_P
    ETH_MD4_N

    They have to be routed 100 Ohms differential, because the ethernet cable has 100 Ohms. I do understand that.

    But what are this RX and TX signals you mention ? Why 50 ohms ?

    Do I have to use micro-vias on the carrier board ??!?
    That would be an argument against using picoZed for me.

  • 0

    The guidelines presented above are ethernet guidelines in general. Your carrier card would be responsible for routing the differential pairs at 100-ohms. The only other ethernet signals on the JX3 connector are the two LED signals that are routed to 50-ohms. The other side of the equation (the RX and TX signals) exist on the PicoZed modules and are already taken care of for you.

  • 0

    Thank you, I understand that.

    Do I need micro-vias on the carrier ?