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DS280DF810: Some added quextions

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Replies: 3

Views: 37

Part Number: DS280DF810

Hello,

Thank you very much for your kindly reply. I have a few other questions as below.

1. The retimer does not terminate the FEC even the CDR disabled?

2. if the CDR is disabled, how much output jitter will increase?

3. Could you please to help confirming the serdes rate and design as the attachment can be supported? (26.5625Gbps\25.78125Gbps\10.3125Gbps\1.25Gbps)

4. For the connection with switch, data should be send to two switch at same time and select one of them to receive. Does it support?

5. what is the max propagation delay?

Thanks a lot!5633.Design with DS280DF810.docx

  • 1. The retimer does not terminate the FEC even the CDR disabled?

    Correct

    2. if the CDR is disabled, how much output jitter will increase?

    The exact amount of jitter increase for CDR enabled vs bypass depends on multiple variables including data rate and input jitter decomposition. The jitter for CDR bypass mode at higher data rate (> 20gbps) may be close to double that of the jitter for CDR enabled  

    3. Could you please to help confirming the serdes rate and design as the attachment can be supported? (26.5625Gbps\25.78125Gbps\10.3125Gbps\1.25Gbps)

    From the list above all of the rates are supported in retimed mode except for 1.25Gbps. The user may set the retimer to CDR bypass mode to operate in 1.25gbps.

    4. For the connection with switch, data should be send to two switch at same time and select one of them to receive. Does it support?

    Yes, I believe so. The DS280DF810 retimer implements a 2x2 Crosspoint on each channel pair supporting fanout, lane crossing, and 2:1 switching.

    5. what is the max propagation delay

    This figure is on the product datasheet. Please download from TI.com DS280DF810 product page

    Cordially,

    Rodrigo Natal

    HSSC Applications Engineer

  • In reply to Rodrigo Natal:

    Hi Rodrigo Natal,

    Thank you very much. your answer is very important and has resolved most question of us.

    But for the propagation delay, only typical value is figured. we want to get the max value for 1588 requirements.

    Youxiang Fang

  • In reply to user3660867:

    Hi,

    Per our design analysis the worst case variation for propagation delay across process voltage and temperature is +/- 20% relative to the typical. So, for 25.78125Gbps the max propagation delay is 1.2*(3.5* +145) = 336.88ps

    PARAMETER

    TEST CONDITIONS

    MIN           TYP           MAX

    UNIT

     

    tD

    Input-to-output latency (propagation delay) through a channel

    No crosspoint; CDR enabled and locked.

    3.5UI + 125ps

     

    ps

     

    tD

    Input-to-output latency (propagation delay) through a channel

    Crosspoint enabled; CDR enabled and locked.

    3.5UI + 145ps

     

    ps

     

    tD

    Input-to-output latency (propagation delay) through a channel

    No crosspoint; CDR in raw mode.

     

    < 145

     

    ps

    Cordially,

    Rodrigo Natal