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DP83867IS: DP83867IS Magnetics Requirements

IDK
Prodigy 230 points
Part Number: DP83867IS

Hello,

I'd like to make sure I understand the magnetics requirements for the DP83867IS in order to implement a discrete solution that meets those requirements. The evalkits for this part seem to use HX5008NL for its discrete solution. This part's datasheet seems to indicate that its return loss is approximately -8dB at 100MHz, whereas your datasheet requirement seems to indicate that the test conditions for the part had a typical return loss of -10dB from 60MHz to 100MHz. Are the datasheet specifications really meant to be closer to guidelines? 

I am thinking about using a part with similar specifications to HX5120NL. I believe this has the same return loss rating as HX5008NL, with worse crosstalk and CMRR performance that HX5008NL. The forum Q&A here https://e2e.ti.com/support/interface/f/138/t/504434 seems to indicate that this part is appropriate. 

Overall, would I be able to use a part like HX5120NL? Should the datasheet requirements for the magnetics be adjusted or seen more as recommendations? I see the magnetics selection as something that's fairly dependent on the operating environment so I suspect a lot of it has to do with that, but having better guidelines for use with this specific set of magnetics would be good.

Thanks,

Matthew

  • 0
    TI__Genius 16030 points

    Hello Mathew,

    Specs of HX5120NL are also ok.

    Most of the magnetics in the market with a few dB deviations will do the job of functional performance with DP83867 as PHY. Choice of magnetic mainly impacts :  electrical compliance test (if that is the requirement) or if you are looking for extended cable reach. Also as you noted, these parameters are also dependent on the board design etc. Hence if you have a multi board design with lot of vias or connectors on path between PHY -> magnetic -> connector + above , then it may be better to keep an option for magnetic like HX5007 or HX5008 for extra margins.

    --

    Regards,

    Vikram