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DS125DF111: 10GBASE-KR to 10GBASE-SR conversion

Harold Steger
Prodigy 190 points
Part Number: DS125DF111
Other Parts Discussed in Thread: DS100DF410, TLK10031, , DS110DF111

I am looking for an IC to use in a 10G Ethernet application to convert a 10GBASE-KR (backplane) interface from a CPU board to into 10BASE-SR interface from an SFP transceiver.  I've seen a design that uses one of TI's 10G Ethernet Retimers (DS100DF410 or DS125DF111) for this purpose.  But I've researched TI's 10G Ethernet transceivers (TLK10031, for example) that seems to be used for the same purpose.  What are the advantages and disadvantages of using one of these Retimers over using one of these transceivers for this application?

  • 0
    TI__Genius 16290 points

    Hi,

    TI's TLK10xxx parts are SerDes transceivers which include a high speed side supporting data rates up to 10.3125 Gbps and a low speed side supporting data rates up to 5 Gbps. In 10GBASE-KR mode, they can serialize 8B/10B encoded XAUI data on the low speed inputs into 64B/66B encoded data on the high speed output, and vice versa. Link training is supported.

    TI's 10G ethernet retimers (DS1xxDFxxx) simply allow each input to pass through a CTLE, DFE, CDR, and driver with de-emphasis. DS100DF410 supports data rates of 10.3125 Gbps and 1.25 Gbps, DS110DFxxx devices support 8.5 - 11.3 Gbps and subrates, and DS125DFxxx devices support 9.8 - 12.5 Gbps and subrates. DS100 and DS110 products include adaptive equalization up to 34-dB boost at 5 GHz. There is no SerDes capabilities and link training is not supported, as these devices are not protocol aware.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 190 points

    Hi Lucas,
    Thanks for this detailed answer.  I appreciate it.

    As I mentioned, I'm trying to interface the 10GBASE-KR interface from a CPU to a 10GBASE-SR optical SFP+ transceiver.  Regarding the TLK10031, I think its XAUI interface is used to interface to 10GbE MAC devices. SFP+ optical transceivers use a SFI interface.  The Applications section of the TLK10031 datasheet indicates,

    "The device can also be used for optical physical layers (like 10GBASE-SR or 10GBASE-LR) by interfacing to optical modules requiring SFI or XFI electrical signaling. For optical use cases, KR-specific features like Clause 73 auto-negotiation and link training should be disabled."

    Is there a reason to use a device such as the TLK10031 instead of the DS125DF111 (Ethernet Retimer) if this application calls for disabling features of the TLK10031 such as link training?

  • 0 in reply to Harold Steger
    TI__Genius 16290 points

    Hi Harold,

    My apologies, I missed the 10GBASE-SR part of your original question. Auto-negotiation and link training should be disabled because they are not supported by 10GBASE-SR. I think your choice between a TLK10xxx transceiver and DS1xxDFxxx retimer should come down to the following questions.

    1. Does your application need to serialize multiple low-speed channels into a high-speed channel? If yes, TLK10xxx is the better choice.
    2. Does your application require 10GbE line rate on both sides of the device? If yes, DS1xxDFxxx is the better choice because the low-speed side of TLK10xxx devices only supports up to 5 Gbps.
    3. Does your application include lossy channels which need good signal conditioning, If yes, DS1xxDFxxx is the better choice.

    Once you have chosen between TLK10xxx and DS1xxDFxxx, I can help with part selection within these product families. I would need you to share your data rate and channel count on both the backplane and optical sides.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 190 points

    Hi Lucas,

    Thanks for clarifying the use cases of these two ICs.  For my application, I need to support 10GbE line rate on both sides of the device so the Ethernet Retimer (DS1xxDFxxx) seems to be the way to go.  In addition, my application supports a single 10GBASE-KR interface going to a single 10GBASE-SR interface.  Would you recommend a different TI device than the DS125DF111?

  • 0 in reply to Harold Steger
    TI__Genius 16290 points

    Hi Harold,

    In that case your best options would be DS110DF111 and DS125DF111. DS110DF111 supports 8.5 to 11.3 Gbps + subrates, DS125DF111 supports 9.8 to 12.5 Gbps + subrates. DS110DF111 may be favorable because it operates at 10.3125 Gbps by default, but both retimers will support your application.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 190 points

    Thanks Lucas.  That's very helpful.