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  • Schematic Confirmation

    Hello! I am really sorry if i disturbed you by my dumb
    question.I'm a beginner so can i ask you a really disturbing point
    for me in the reference schematic from texas instruments for 4-port
    hub.
    So in the picture they told they intentionally reversed
    polarities for diff pairs.
    1) Why would they do that? Is this right thing to do this?
    2) Can i use this in my schematic? What will happen if i don't reverse
    the polarities?

    Best Regards!
    Attached Files

  • #2
    i have no idea why you should reverse the polarity.. can you share the link to were you found that? also there seems to be some connections from your esd diodes that doesnt seem right.. usually when there is an NC connection it means Not Connected.. so i would suggest to remove those lines.

    Comment


    • alienock
      alienock commented
      Editing a comment
      No sir I think I know that the esd protection can be used just for the flow through routing(signals entering from one side and going out from other side).Is this right?
      And here's the link for this document:
      https://www.ti.com/lit/ug/tidu614/ti...252FTIDA-00288

  • #3
    Looks like USB 3.0 specification is mentioning this:
    Source: https://www.usb3.com/whitepapers/USB...008)-final.pdf

    6.4.2 Lane Polarity Inversion
    During the TSEQ training sequence, the Reciever must use the D10.2 Symbol within the TSEQ Ordered Set to determine lane polarity inversion (RXP and RXN are swapped).


    But, I believe, that will not work with USB2.0, only for USB 3.0 TX/RX signals. Usually this is for easier layout.

    Where is the schematic from? It may be oki.

    Comment


    • alienock
      alienock commented
      Editing a comment
      Sir here's the link for this:
      https://www.ti.com/lit/ug/tidu614/ti...252FTIDA-00288
      Sir i am just confused, because i'm using altium,so when i make a pair of diff signals(TX_N,TX_P) the polarity is reversed(TX- is TX_P & TX+ is TX_N) at the end.
      So what I can do?Should I use the reversed polarity signals or not?

  • #4
    You can follow TI design. That design should be ok - means, you should be fine when you swap USB3.0 TX (RX) positive and negative lines the same way as done on the reference board.

    i'm using altium,so when i make a pair of diff signals(TX_N,TX_P) the polarity is reversed(TX- is TX_P & TX+ is TX_N) at the end.
    - where is it reversed?

    Comment


    • alienock
      alienock commented
      Editing a comment
      Sir in the attached image on my first post there is TX- first label as SSTXM but at the end it is labeled as SSTXP. Same case for the TX+, RX+ & RX-.
      My question is, what if i dont swap the polarities? Will i be fine? Is there any problem if i dont swap polarities?

  • #5
    No, there will be no problem when you do not swap polarities. I believe the did it to make layout easier.

    Comment

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