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DS250DF410: supported optical module question?

Tess Chen
Intellectual 2675 points
Part Number: DS250DF410
Other Parts Discussed in Thread: DS560DF810, DS280DF810

DS250DF410: Are below 4 optical modules supported?

  • 100G: 100G of C2M, CAUI-4 (baud rate: 25.78125GBd) and GAUI-4 (baud rate: 26.5625GBd)?
  • 50G: 50G of C2M, LAUI-2 (baud rate: 25.78125GBd) and GAUI-2 (baud rate: 26.5625GBd)?

Thanks for the clarification. 

  • 0
    TI__Mastermind 19235 points

    Hi,

    The DS250DF410 supports IEEE chip-to-chip and chip-to-module interfaces running at 25.78125GBd NRZ rate per channel. But it does not support 26.5625GBd PAM4. For PAM4 support  TI has the DS560DF810 retimer part number. See link below.

    https://www.ti.com/product/DS560DF810

    Regards,

    Rodrigo Natal

  • 0 in reply to Rodrigo Natal
    TI__Intellectual 2675 points

    Thanks for your prompt reply.

    Does this device support below topology?

    host -（25.78125GBd NRZ *2lan）-re-timer-（26.5625GBd NRZ*2lan）- module（QSFP28)

  • 0 in reply to Tess Chen
    TI__Mastermind 19235 points

    The DSS560DF810 support Gearbox function to convert 2 x 25.78125GBd NRZ lanes to 1x26.5625GBd PAM4 lane. See below datasheet texrt:

    The DS560DF810 is equipped with a bit mux and de-mux gearbox for simple NRZ-to-PAM4 or PAM4-to-NRZ
    conversion between host and module. The gearbox is capable of aggregating a pair of NRZ inputs up to 28.9
    GBd into one 28.9 GBd PAM4 output as well as de-aggregating a single 28.9 GBd PAM4 input into a pair of 28.9
    GBd NRZ outputs.

    Table 8-1. Gearbox Modes of Operation

    MODE(1)

    INPUT(S)

    OUTPUT(S)

    COMMENTS

    Bit Mux

    Two streams of NRZ data from RXA and RXB operating up to 28.9 GBd NRZ

    One stream of PAM4 gray-encoded data at the same baud rate

    The PAM4 output can be driven on either TXA or TXB.

     

    Bit De-mux

    One stream of PAM4 data from either RXA or RXB operating up to 28.9 GBd gray-encoded PAM4

    Two separate streams of NRZ data at the same baud rate

    The NRZ outputs are driven on TXA and TXB.

     

    Bit Serializer

    Two streams of NRZ or PAM4 data from RXA and RXB operating up to 14.45 GBd

    One stream of data at double the baud rate with input modulation type (NRZ or PAM4) maintained

    The output (NRZ or PAM4) can be driven on either TXA or TXB.

     

    Bit Deserializer

    One stream of NRZ or PAM4 data from either RXA or RXB operating up to 28.9 GBd

    Two separate streams of data at half the baud rate with input modulation type (NRZ or PAM4) maintained

    The outputs (NRZ or PAM4) are driven on TXA and TXB.

    (1)  Retimer gearbox supports user-configurable mapping for NRZ-to-PAM4 and PAM4-to-NRZ.

  • 0 in reply to Rodrigo Natal
    TI__Mastermind 27632 points

    Hi Tess,

    I would like to make a correction to the response above.  After discussing DS560DF810 gearbox behavior further with Rodrigo, we believe that the gearbox only supports conversions between NRZ and PAM4 with a constant baud rate.  For example, 2 x 25.78125 GBd NRZ <-> 1 x 25.78125 GBd PAM4, or 2 x 26.5625 GBd NRZ <-> 1 x 26.5625 GBd PAM4 are possible with this device, but conversions between 25.78125 GBd and 26.5625 GBd are not possible.

    This is also supported by the following table from the datasheet.

    Thanks,
    Drew

  • 0 in reply to Drew Miller1
    TI__Intellectual 2675 points

    Does DS250DF410 support 26.5625GBd NRZ(not PAM4)?  I assume that DS280DF810 could support but DS250DF410 not? Thanks.

  • 0 in reply to Tess Chen
    TI__Mastermind 27632 points

    Hi Tess,

    Yes you are correct, the DS250DFx10 will not lock to 26.5625 GBd NRZ since this is outside of the range of the CDR system.  The DS280DF810 does support this.

    Also, some of your questions seem similar to another thread, so I have linked it for reference.

    https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1190947/ds110df410-does-ti-s-retimer-guarantee-that-the-input-serdes-signal-is-at-the-same-frequency-as-the-output-serdes-signal

    Thanks,
    Drew