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DS125BR820: Can DS125BR111 or DS100BR210 used with DS125BR820?

ZhongHe Jin
Prodigy 80 points
Part Number: DS125BR820
Other Parts Discussed in Thread: DS125BR800A, , DS125BR111, DS100BR210, DS100BR111, DS110DF111

Hi, I want to use one 8ch Repeater at main board and 2 ch repeater at line card. If DS125BR820 (or DS125BR800A) is used at main board, how to select the 2ch repeater chip at line card? Is DS125BR111 suitable? 

Is there any selection guide about repeaters or retimers?

In our design, we have 10G SFP+ line card and 5G QSGMII card. The SFP+ card has 4 SFP+ module and 4 SFP+ lanes. The QSGMII card has 1 QSGMII channel. What is the recommended repeater or retimer chipset for my design?

Thanks a lot.

  • 0
    TI__Mastermind 29635 points
    Hi ZhongHe,

    Selecting the repeater depends predominantly on the following:

    1. Which protocol are you running?
    2. What are the number of lanes/channels required?
    3. What is the maximum data rate?

    Based on your use case of the repeater in 10G SFP+ and 5G QSGMII applications, I recommend the following selection guide: www.ti.com/.../snla225.pdf

    Note also that this guide was released before the DS125BR820 and DS125BR111 advanced linear repeaters were released. These devices provide a higher level of linear equalization compared to previous generations (DS125BR800A, DS100BR210, DS100BR111), which is especially useful in applications where LInk-Training is required. Note that the advanced linear equalization comes at the expense of reduced maximum CTLE gain.

    Do you have a block diagram showing how much insertion loss is expected from endpoint to endpoint in your system? Seeing this will help us confirm whether the DS125BR820 and DS125BR111 are the best fit.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Prodigy 80 points

    Hi, Michael

    Bellow is the system diagram. Maximum 10G trace length is about 10000mil, and MAX 5G trace length is about 20000mil. 

    The insertion loss of the connector is about -1.8dB at 10GHz and the return loss about -10dB at 10GHz.

  • 0 in reply to ZhongHe Jin
    TI__Mastermind 29635 points
    Hi ZhongHe,

    Since the maximum trace length is 10 inches (10G) and 20 inches (5G), I recommend the DS125BR820 or DS125BR111 for your application.

    If you require a retimer for this application, I recommend the DS110DF111. Note that the retimer does not support link-training, though I do not think this will be an issue in your application. Link-training is a requirement for IEEE802.3 10G-KR (Ethernet backplanes), but from your description, it seems like this protocol is not used by your line cards.

    Regards,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Prodigy 80 points

    Hi, Michael

    When place the repeaters, shall I put them at the RX side? That is for TX path, put the repeater at the line card, and for RX, at the main board. 

  • 0 in reply to ZhongHe Jin
    TI__Mastermind 43795 points
    Hi Zhonghe,

    I would put them close to the receive side of the datapaths. This gives the repeater CTLE the most linear response.

    Regards,
    Lee