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Redriving SFP outputs

Jameson Collins
Prodigy 70 points
Other Parts Discussed in Thread: TLK6201EA, TLK1101E, SN65LVCP402, TLK1102E, SN65LVDS100, DS100BR111, DS100KR401, DS100KR800, DS42BR400

I am developing an external carrier to connect gigabit SFP modules to my FPGA. SFPs have integrated coupling capactiors, but my FPGA inputs already have coupling capactiors and I dont want to connect these capacitors in series.  I'd like to put either a buffer or repeater on the output and input of the SFP modules.  Can anyone suggest a product for this?

  • 0
    TI__Mastermind 20820 points

    Hi Jameson,

    I understand your concern with the two capacitors in the signal path.

    Take a look at the TLK6201EA and TLK1101E for use in your design. Let me know what you think and I can recommend some more parts for you if need be.

  • 0 in reply to Michael Peffers
    Prodigy 70 points

    Thank you for the links Michael.  I believe that the TLK6201EA would likely get the job done. 

    In my application the distances are short (<1m of cable) and the speeds are low (<=1Gbps).  I believe there will be little signal degredation and the signal equalizer may not be needed.  Do you agree with this, and if so, can you recomend a product which doesnt have the equalizer but may have multiple channels (i.e. a tx and rx path)?

  • 0 in reply to Jameson Collins
    TI__Mastermind 20820 points

    Hi Jameson,

    The equalizer in the TLK6201EA can be disabled for 0 dB gain by tying the DE0 and DE1 pins to ground. Unfortunately I do not have a multichannel variant of this part.

    We do however have the TLK1102E which is a 2 channel buffer/equalizer similar to the TLK6201EA. The equalizer can be disabled via I2C or GPIO. Also, take a look at the SN65LVCP402. This is a non blocking cross point switch that allows for any input to be routed to any output. It is a self biasing device like the TLK1102E and TLK6201EA so not external components are needed with it. The equalizer can also be bypassed in this device via GPIO.

    The other approach that I am think of using requires a device like the SN65LVDS100 which has a bandwidth of up to 2Gbps. For this type of application though you would have to set the input common mode level through the use of an external termination network as the input common mode spec ranges from 0-4V.

  • 0
    TI__Expert 3050 points

    Hi Jameson,

    What data rates or protocols are you trying to support?

    TI has many 10G or 12G buffers in various multichannel configurations that you could use.

    Please look at the DS100KR800, DS100KR401, DS100BR111.

    i recommend taking a look at www.ti.com/sigcon

    Mike Wolfe

    DPS APPS / SVA

  • 0 in reply to Mike Wolfe
    Prodigy 70 points

    1000base-bx

    Of the options you listed the DS100KR401 would meet my needs well (4xbidi).  However since this is a fairly slow, and neither space nor power constrained application, I'd like to use whatever is the most 'simple' implementation.

  • 0 in reply to Jameson Collins
    TI__Expert 3050 points

    Hi,

    TI also has a large selection of repeaters that support up to ~3Gbps.

    Another device you could consider would be the DS42BR400.

    There are many parts available under the repeater/redriver section at www.ti.com/sigcon

    Mike Wolfe

    DPS APPS / SVA

  • 0 in reply to Mike Wolfe
    Prodigy 70 points

    I went ahead and designed the board with the TLK6201EA.

    Can someone confirm that this chip is already terminated for connections to 100-ohm differential transmission lines on the input and output and therefore wont require any termination or series resistors for Z_0 matching.

  • 0 in reply to Jameson Collins
    TI__Mastermind 20820 points

    Hi Jameson,


    Can you please help me understand more about you, your company and your application? You can ping me offline at mpeffers@ti.com

  • 0 in reply to Jameson Collins
    TI__Mastermind 20820 points

    Hi Jameson,


    Closing this post since the conversation has moved off line.