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DS125BR401A: Redriver(Equlizer) for PCIe Gen3×８

ttd
Mastermind 9275 points

Part Number: DS125BR401A
Other Parts Discussed in Thread: DS160PT801, DS125BR820, DS125BR800, DS80PCI800, DS125BR401, DS80PCI810

Tool/software:

Dear Technical Support Team,

I need a PCIe Gen3 x 8 lane redriver (equalizer).

Is it possible to use two DS125BR401A for 8 lanes of Gen3?

Please let me know if there are any appropriate redriver products for PCIe Gen3 x 8 lane.

Retimers like DS160PT801 also include CDR, which I think is more complex and has limitations.

what is the difference between retimer(like DS160PT801) and a redriver(like DS125BR401A )?

Best Regards,

ttd

  • 0
    TI__Mastermind 32310 points

    Hi ttd,

    Yes, 2 pcs DS125BR401A can be used to support PCIe Gen3 x8. Note that this device is unique because each side has a different die design. The A side is highly linear but has limited EQ boost capability, up to 9.3dB @ 4GHz. The A side uses the same design as DS125BR820. The B side is is less linear/more limiting but has higher EQ boost capability, up to 31.6dB @ 4GHz. The B side uses the same design as DS125BR800.

    Linear redrivers have great input-to-output linearity which is best suited for PCIe Gen3 and higher. Waveform linearity is necessary to transparently pass through feedback protocols such as link training. Limiting redrivers do not maintain waveform linearity, but include amplitude and de-emphasis control on the TX side of the device. Many of our limiting redrivers do include a linear mode which can be used with PCIe Gen3, however it may be more difficult to get link training sequences to pass through successfully.

    If your application does not require larger EQ boost, I recommend using linear redrivers such as DS125BR820 or DS80PCI810. If your application does require larger EQ boost, I recommend using redrivers such as DS125BR800, DS125BR401, or DS80PCI800 in PCIe Gen3 (linear) mode. If your application requires larger EQ boost on one side and lower EQ boost on the other side, then DS125BR401A is your best option.

    Redrivers perform signal conditioning through equalization, providing compensation for input channel loss from deterministic jitter such as inter-symbol interference. Retimers are mixed-signal devices that include equalization functions plus a clock and data recovery (CDR) function to compensate both deterministic and random jitter, and in turn transmit a clean signal downstream. DS160PT801 is our PCIe Gen3/Gen4 retimer which includes a state machine to actively participate in link training. Although DS160PT801 has the added benefit of random jitter compensation, the bringup complexity is significantly more challenging than our redrivers. Additionally a redriver provides adequate signal conditioning for many Gen3 applications.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Mastermind 9275 points

    Hi Lucas,

    Thank you for your detailed infomation for Gen3 8lane.

    I’d like to use two DS125BR401A to configurate a Gen3 8lane based on your mentions.
    So I have an additional question.

    The ENSMB pin has two modes.
    I have used one DS125BR401A before and then it was set to TERMINAL MODE.

    Can I use the same TERMINAL MODE setting when I use two DS125BR401A for Gen3 8lane ?

    Is there any limitation that the clock source must be the same for two DS125BR401A ?
    (For example, the clock from the FPGA is divided into two systems with a buffer and input to each IC)

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Guru**** 189101 points

    Hi ttd,

    Due to the US Christmas and New Year holiday, the response to your question will be delayed. Sorry for the wait and any inconvenience it may cause.

    Thanks,

    David

  • 0 in reply to David (ASIC) Liu
    TI__Mastermind 32310 points

    Hi ttd,

    Yes, you can use terminal mode for a PCIe Gen3 application. I do recommend including a pull-up resistor footprint on the ENSMB pin and headers to access SDA and SCL pins, so SMBus slave mode can still optionally be used. Having access to registers with SMBus slave mode can be greatly helpful for debug.

    DS125BR401A does not require any clock input.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Mastermind 9275 points

    Hi Lucas,

    Thank you for you reply.

    I send the schematic internaly about two DS125BR401A.

    Could you check it and if you have any concern, please let me know.

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Mastermind 32310 points

    Hi ttd,

    Unfortunately my E2E private messages are currently bugged and I'm unable to see your message. Can you send me the schematic via email? I can review and follow-up through email.

    Best,

    Lucas

    l-wolter@ti.com

  • 0 in reply to Lucas Wolter
    Mastermind 9275 points

    Hi Lucas,

    Thank you for your reply.

    I attached schematic through E-mail.

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Mastermind 32310 points

    Thank you, I will get back to you via email.