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DS560MB410: Is DS560MB410 can be configured to support 1:2 fanout?

wenbo shen
Prodigy 10 points
Part Number: DS560MB410
Other Parts Discussed in Thread: DS560DF810,

Hi, 

I want a 1:2 fanout buffer to support PCIe analyzer scenario. In applications such as TAP, protocol analyzer, such fanout buffer is useful. Please refer to

 Lecroy’s products( https://teledynelecroy.com/protocolanalyzer/pci-express).

 

A simplified system diagram is shown below (it’s an x1 PCIe system).

 

 

 

So what we need is not a PCIe switch, conceptually ,it’s a simply fanout buffer which supports 32Gbps (at least 16Gbps) NRZ signaling . It can be a real electrical level 1:2 fanout buffer, or a redriver, or a retimer, the only requirement is that it can output two copies of the high speed NRZ serial input signal simultaneously.

 

We expect the buffer can support PCIe Gen4(16GT/s) and Gen5(32GT/s) support is highly preferred.

 

I’m wondering if DS560MB410/DS560DF810 can be configured to meet this requirement (DS560MB410 shown as below).

 

 

Do you have any other recommendations ? Is any chip in your categories of Ethernet interface and PCIe interface  ok?

Thanks

--Wenbo

 

  • 0
    TI__Mastermind 20192 points

    Hi Wenbo,

    The DS560MB410 is the best device we have for this application.  However, implementing it in PCIe is not straightforward.  Since it is designed for Ethernet applications, it does not have some of the PCIe specific design considerations found on PCIe redrivers.  It does not have an RX detect circuit, and the RX termination is 100 Ohm differential, while PCIe have two 50 Ohm singled ended to an internal common mode voltage.  It may be possible to find work arounds for some of these PCIe specific issues.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 10 points

    Hi, Drew,

    Thanks for your replay. As per your explanation, DS560MB410 can be configured to support 1:2 fanout, but for PCIe applications ,some PCIe specific issues must be considered and solved. it's really a good news for me.

    Another question for you ,does the CDR in DS560MB410 can lock to 32Gbps/16Gbps?

    Have a nice day.

    --Wenbo

  • 0 in reply to wenbo shen
    TI__Mastermind 20192 points

    Hi Wenbo,

    Yes your understanding is correct, the DS560MB410 can provide 1:2 fanout, but some PCIe specific issues must be considered / solved.  The DS560MB410 is a linear redriver.  It does not have any CDR, so there is not a need to worry about CDR lock.  It also has very low latency.  An advantage of being a linear redriver is that it is able to transparently pass through different pre/post TX settings used in link training. Per datasheet, it is suitable for up to 32 GBd NRZ signaling.  I would expect it to work fine for 32 Gbps and 16 Gbps signaling.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 10 points

    Hi, Drew, 

    I'm sorry that another question just came to me. DS560MB410 is just a linear redriver without a CDR, will this have any negative impact on SI? Will the eye diagram be hard to control when running at 32Gbps? I wound expect DS560MB410 has taken this into consideration and SI is not an issue.  Hope this is my last question. :)

    Thanks

    --Wenbo

  • +1 in reply to wenbo shen
    TI__Mastermind 20192 points

    Hi Wenbo,

    Happy to help answer your questions.  The DS560MB410, similar to our other linear redrivers, has CTLE to compensate for channel insertion loss.  This device is designed to reduce ISI from insertion loss.  Since it does not have a CDR, it will not have a clean of an output as a retimer.  If your system's channel loss is within what the DS560MB410 can compensate for, I would expect good SI.

    Something that might add confidence to your design is to simulate the channel using our IBIS-AMI model.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 10 points

    Hi, Drew, 

    I got all the info I need about DS560MB410 and I think this thread can be closed. Really appreciate your detailed reply and time. 

    Thanks

    --Wenbo