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VCC - GND connection for TPD8S009

rifo
Expert 1105 points
Other Parts Discussed in Thread: TPD8S009

Hello,
For a high speed video display application,  I am planning to use TPD8S009  between a LVDS connector and a FPGA.  Am I right in saying that   Vcc of  TPD8S009 should be connected to the supply voltage of the corresponding FPGA bank (where the LVDS signals are routed)?


e.g,     LVDS connector     ----- >   TPD8S009   -------------->  Spartan 6LX75,  Bank 0

for the above configuration,  supply voltage of Bank 0 is 2.5V  hence Vcc of TPD8S009 should be 2.5V too

Also, for GND connection, is it okey to connect GND of TPD8S009 directly to system GND?   Do I need some kind of extra circuitry there?


Thanks a lot for your help

rifo

  • 0
    TI__Genius 12190 points
    Hi rifo,

    Yes, in this case you should use a Vcc = 2.5 V. Regarding the ground, it is always best to have the analog/digital/chassis grounds separated by some inductance. The correct ground to use for the TPD8S009 would be the chassis ground. You want to put the TPD8S009 as close to the connector as possible. The connector should be part of chassis ground, so that the TPD8S009 has access to the Chassis ground.
  • 0 in reply to Guy Yater
    Expert 1105 points

    Hello,

    Thanks for the answer. What if the LVDS connector doesn't have a chassis gnd connection. In that case, what do you recommend?

    thanks a bunch for your help

    cheers

  • 0 in reply to rifo
    TI__Genius 12190 points

    Hi Rifo,

    That's a very good question. The answer is to place TPD8S009 as close to the connector as possible. Hopefully the cable attaching to the connector has a good ground, like a shield. With this scenario, you are helping TPD8S009 have a low impedance ground return path for any ESD. Please have a look at ESD Protection Layout Guide  which covers all of the concerns for the PCB designer regarding ESD.

    Regards,

  • 0 in reply to Guy Yater
    Expert 1105 points

    hello again Guy,

    Thanks a lot for your help!   I'll keep your advice on the topic.

    cheers

    rifo