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DS90UB913A-Q1: DS90UB913A-Q1

Yervand Prazyan
Prodigy 40 points

Part Number: DS90UB913A-Q1

HI,

I am  considering using DS90UB913A-Q1 with SPF module.I planing to have direct connection between out of  DS90UB913A-Q1 and input of SPF module.From data sheat of spf module I noticed that required voltage swing on input lines will be between 400 and 2000mV differential,and output swing of DS90UB913A-Q1 can be between 640mV and  824mV  differential.

http://www.ti.com/sitesearch/docs/universalsearch.tsp?searchTerm=DS90UB913A-Q1#q=DS90UB913A-Q1&t=everything&linkId=1

So I need some advise ,can I have this direct connection or I need some interface converter maybe?

Cheers,
Yervand Prazyan

  • 0
    TI__Guru** 103215 points

    Hello Yervand,

    Usually FPD-Link devices are to be used as a pair and the channel includes both forward and reverse communications when connected to a deserializer. If you try to go through an SPF module the FPD-Link protocol will be broken so I would not advise this. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 40 points

    Hi Casey ,

    Thank you so much for reply and help.

    So ,do you meant that when I will try to connect out of SPF module to deserializer then FPD-Link protocol will be broken?

    So do you have any suggestion for those type cases?Because anyway I am not clear why we cannot use this connection,or maybe we can use serdes with LVDS(IN/OUT,but as I make sense LVDS very close to FPD-Link protocol )

    Again,thanks for your valuable advise!

    Regards,

    Yervand

  • 0 in reply to Casey McCrea
    Prodigy 40 points

    Hi all,

    Also TI technical support consultation required.

    Regards,

    Yervand

  • 0 in reply to Yervand Prazyan
    TI__Guru** 103215 points

    Hello Yervand,

    You can learn more about FPD-Link III here: https://training.ti.com/ti-precision-labs-what-is-fpd-link?context=1139747-1138099-1139854-1139837 

    FPD-Link III is a bidirectional protocol which requires an electrical link between SER and DES. If you add an optical module in-between then the bidirectional control channel will not function properly because SPF modules are unidirectional. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 40 points

    Hi Casey,

    Thank you for information and your help.I will try to be more clear.So below functional schems.So my concern is that I will have some incontinence between out of Serializer and input of SFP,and other side ,between out of SFP and input of DESerializer.

    RD-/+: These are the differential receiver outputs. They are AC coupled 100Ω differential lines which should be terminated with
    100Ω (differential) at the user SERDES. The AC coupling is done inside the module and is thus not required on the host board.
    The voltage swing on these lines will be between 400 and 2000mV differential (200–1000mV single ended) when properly
    terminated.

    TD-/+: These are the differential transmitter inputs. They are AC-coupled, differential lines with 100Ω differential termination
    inside the module. The AC coupling is done inside the module and is thus not required on the host board. The inputs will accept
    differential swings of 400–2000mV (200 – 1000mV single-ended).

    .

    Reards,

    Yervand

  • 0 in reply to Yervand Prazyan
    TI__Mastermind 30515 points

    Yervand,

    If you use SFP module between FPD-Link Ser and Deser, it means only single-direction is used here. For FPD-Link, some setting should be supported based on the negotiation between ser. and deser after power-on, so this is why Casey says it is not allowed for such application.

    in the other way, in the block as you figured, the function can work, but it needs some register settings since the link is not negotiated by bi-directional communication based on modesel setting (this is called as hardware strap setting after power on). Dependent on the selected ser. and de-ser in your case, you need set the reg. to replace the strap function from the mode_sel pin of ser/de-ser.

    also, one concern in your case is that the data rate. as I know, the sfp module has specific data rate design request, I don't know if in your system, the video PCLK and its serial rate in FPD-Link channel can be aligned with your SFP's module rate or not?

    bset regards,

    Steven