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Original question:

MUX SGMII WITH DS125MB203

DS15MB200: DS15MB200 Used for SGMII Multiplexer

Dominic Lisi
Prodigy 70 points
Part Number: DS15MB200

I found some old threads from 2014 talking about using this chip, DS15MB200, for an SGMII Mux. I was wondering if this was an acceptable solution to needing a SGMII MUX. If so are there any reference designs or anything like that out there that I didn't find? I'm just wondering how to properly hook up the termination, etc.

I also found several other threads asking similar questions that have just flat out wrong information about this topic - as answers from "mastermind". SGMII is a 2 pair interface that runs at 1.25 Gbps. I found several posts directing people to 14 bit DDR muxes as the answer...or referring to the RGMII spec when people clearly asked about SGMII - which...is again, wrong.

  • 0
    TI__Mastermind 43795 points

    The DS15MB200 would work well, it is capable of supporting the SGMII interface.  Sorry some of the older posts were inaccurate.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 70 points
    Thanks for the quick reply about this Lee.

    I was hoping to find some design information about it. Admittedly my termination knowledge is lacking. I'm assuming I can't just hook the AC Coupled SGMII signals into this device and there would need to be some sort of DC termination since it's LVDS? - and I don't know what that is (if any is required..)
  • 0 in reply to Dominic Lisi
    TI__Mastermind 43795 points

    You can set the voltage level with a resistor divider to end up at ~ 1.2V common mode at the input of the LVDS device.  The DS15MB200 includes a 100 ohm internal differential termination. 

    You can also try it with the resistors removed,  we have had success in the lab AC coupling this device without any input bias.

    Regards,

    Lee 

  • 0 in reply to Lee Sledjeski
    TI__Mastermind 43795 points

    For the input side of the DS15MB200 the actual connection would be determined by the electrical characteristics of the driving device.  The DS15MB200 is a LVDS device with a wide input common mode range.  Most devices can drive the DS15MB200 directly which simplifies the design.  On the output side the DS15MB200 has a 1.2V common mode.  This is compliant with SGMII interfaces so I think you may be able connect it directly as well.  If you are unsure, please post the electrical characteristics of the SGMII devices and I can help work out if any adjustments will be needed.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    TI__Guru* 93670 points
    Hi Dominic,
    Given Lee's comments, i believe we can close this case. Please re-open if there is additional questions.
    Regards,,nasser