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About SerDes and cascade Crosspoint Switch connection

Satoshi
Guru 19495 points
Other Parts Discussed in Thread: SN65LVDS250, DS92LV18

Customer will use DS92LV18 and SN65LVDS250 below connection.

Are these "cascade" crosspoint switch no problem?

And, is the place of termination resistor correct?

Best regards,

Satoshi

  • 0
    TI__Genius 11280 points

    Hello Satoshi,

    Take in account that the DS92LV18 is a receiver/transceiver and the SN65LVDS250 is a unidirectional Crosspoint switch.

    Also for the LVDS250, 50 ohms termination resistor input is recommended and a 100 ohms termination resistor output is recommended.

    Please let me know if further help is needed.

    Regards,

    Gerardo

  • 0 in reply to Gerardo
    Guru 19495 points

    Garard-san

    Thank you for reply.

    Please let me check about termination resister below;

    ①Are Input / Output termination mean DS92LV18 input and output?

       For example, DS92LV18's LVDS input line connect 50Ω and output line connect 100Ω.

    　Or, is termination resister based on crosspoint switch? (Below image? Red point is termination resister.)

    ②About input termination, I think that IN+ and IN- connect separately 50Ω to GND, is it correct?

    ③Is input line necessary termination resister?

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    Guru 19495 points
    Any update on this?
  • 0 in reply to Satoshi
    Prodigy 80 points
    Hi Satoshi, the input terminations could be 50Ω to ground but then you would need to ac couple after the terminations - also, you would load the serdes output - the T version of the crosspoint just has 110Ω across the lines. Still need to consider the dc levels from the serdes but at 1.2V bias this is OK
  • 0 in reply to Dave Leyland
    Mastermind 6365 points

    Hi,

    and quesiont is unused LVDS-input pins of SN65LVDS250.
    (Unused pins: 3A,3B and 4A,4B)

    Which is better for them?
    (open or pullup/down)

    best regards

  • 0 in reply to cafain
    TI__Genius 11280 points

    Hi Cafain,

    The LVDS250's unused pins can be tied to GND both inputs and outputs.

    Regards,

    Gerardo

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