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Switch of DisplayPort signals through a TS3DV20812

Jean Voisin
Prodigy 30 points
Other Parts Discussed in Thread: TS3DV20812, TS3DV621, TS3DV642

We are using a TS3DV20812 differential switch to route, between two ICs, DisplayPort signals at 2.7 Gbit/s per lane (over 2 lanes). On the prototypes, this seems to work fine. However we noticed recently that the TS3DV20812 was specified up to only 2.2 Gbit/s (against the 2.7Gbit/s effective bit rate). Is this a real issue, taking into account that the switch does not drive a cable but interconnects, on a single board, two ICs that are close to each other ?  Has someone experience with that kind of configuration ? Thanks.

  • 0
    Prodigy 30 points

    Hello,

    This is not actually an answer : just some more input to the question that i submitted some weeks ago.

    When comparing the frequency response of the TS3DV20812 with the frequency response of the TS3DV621 (that is certified for DisplayPort signals), it is all but evident why the first one could not also cope with 2.7 Gbit/s. It seems that both parts have almost the same bandwidth.

    TS3DV20812 frequency response

     

    TS3DV621 frequency response


     Thank you in advance if someone could clarify this.

    Jean

     

  • 0 in reply to Jean Voisin
    TI__Expert 6395 points

    Hello Jean,

    I see what you are describing with the frequency response plots.  It is possible the incorrect figure was load into the TS3DV621 and I will have to look into this further.

    As for using these devices for Display Port, if your system is working with no issues then I would say continue as is.  As this device was released some time ago, it is quite possible that the actual performance of the switch is better than the datasheet values/graphs.  This is going to be largely due to layout techniques and that the device was likely characterized on a generic board where the performance of the board was not on par with the switch.  If I had to guess I would say your layout on your board would be better than the char board used.

    As we moved into higher speed switches we found that we had to change the way we approached the characterization of the devices.  Newer devices have their own specialized boards specifically designed to minimize the impact of the board so we can measure the true performance of the device.

    If you are very concerned with your performance margins then it may be wise to upgrade to a better switch.  The TS3DV642 is a new device with > 6.5 GHz BW and will easily handle the 2.7 Gbps of Display Port. I don't know if current consumption is important for your application but the TS3DV642 also has a much lower ICC at 80 uA!

    I hope this provided some insight and I sincerely apologize your first post was missed.

    Regards,

    Andrew

  • 0 in reply to Andrew_Mason
    Prodigy 30 points

    Hello Andrew,

    Thanks a lot.  This is really a valuable answer to me.

    Jean