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EVAL2111EBZ Isolation transformer

Category: Datasheet/Specs


EVAL2111EBZ involves 74930000 as an isolation transformer and 744242471 as a common mode inductor filter. I’m astonishing why I can't use just (i.e) SM91072AL-E as an isolation transformer – inductor set.

Could you please describe me if there was a technical problem that makes you decide on the discrete solution? If not do you recommend me to use SM91072AL-E instead?

Because in my board I have both the 10base-TL and 10base-T1L it would be so much helpful for me to use 1 type of transformer for both the protocols in same speed and also to save the board space.

Thank you for your time and considerations

with the best regards

  • Hi Mehdi,

    The choice between a CM choke and/or transformer depends on the required EMC performance and electrical specifications in the 10BASE-T1L standard (These characteristics must be met by any 10baset1l device).
    Both CM choke and transformer are used to enhance EMC robustness. EVAL2111EBZ can be used as a reference design, but you could use any CMC-Transformer solutions (in same package if found) as long as they meet the required specification.

    10BASE-T1L is single pair, thus a single 74930000 iso transformer is used. However, in the case of SM91072AL-E, it incorporates two transformers within the package, designed for 100Base-T.
    Regarding the compatibility, SM91072AL-E's specifications show insertion loss from 1-100MHz and return loss from 1-40MHz, while 10BASE-T1L specifications start at 100kHz for both parameters.

    It can potentially work, but it's an untested solution that uses devices with specifications that do not cover the frequency range of interest for the 10BASE-T1L signals. So, we cannot confirm its effectiveness.

    Though it may work, it may violate some of the specifications such as MDI Return Loss, Tx Output droop, etc.

    We recommend a CMC of 400uH or higher and Transformer of 350uH or higher for best performance.

    Hope this helps!



  • Hello Shazia,

    Thank you so much for your informative and comprehensive answer!

    With the best regards,