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HD3SS3220: SS signal polarity

Shmuel Davis
Expert 2920 points
Part Number: HD3SS3220

In the data sheet it states :-

Note: HD3SS3220 Does Not Care
About Differential Pair Polarity

Thus if I swap \ cross the TX1p with the TX1n signals like shown in Figure 12, does the Rx1p and Rx1n signals have to be swapped \ crossed as shown OR is there no correlation between the swapping of the individual pairs and if I need to I can swapped only the Tx and leave the Rx with the "correct" polarity ?

  • 0
    TI__Genius 16150 points
    Hi Shmuel,

    There is no issue with swap polarity, for USB specification all the USB3 PHYs must be able to detect any polarity inversion and compensate it. And from our device's perspective, there is no issue since the HD3SS3220 is a passive switch and does not deal with the information on the SS lanes.

    Best Regards,
    Luis Omar Moran
    High Speed Interface
    SWAT Team
  • 0 in reply to Luis Omar Moran
    Expert 2920 points
    Dear Luis,

    Thanks for this reply.

    "for USB specification all the USB3 PHYs must be able to detect any polarity inversion and compensate it. And from our device's perspective, there is no issue since the HD3SS3220 is a passive switch and does not deal with the information on the SS lanes"

    Does this mean that if I route my TX1n signal to pin 17(SSTX1p) and my TX1p signal to pin 16(SSTX1n) of the HDSS3220 then the HDSS3220 will route my TX1n signal out on pin 6 (SSTXp) and my TX1p signal out on pin7(SSTXn) when the Type C connector is plugged in 1 direction,

    BUT

    If the type C connector is plugged in the other direction

    and if I route my TX2n signal to pin 20(SSTX2n) and my TX2p signal to pin 21(SSTX2p) of the HDSS3220 then the HDSS3220 will route my TX2n signal out on pin7(SSTXn) and my TX2p signal out on pin 6 (SSTXp)

    ????

    Shmuel
  • 0 in reply to Shmuel Davis
    TI__Genius 16150 points

    Hi Shmuel,

    In USB3 you can swap polarity and the receiver's physical layer will compensate it, regardless of the used PHY.

    For non-USB3 PHYs you can swap polarity at the input and have to swap polarity at output again to go back to the original state.

    Regards,
    Luis

  • 0 in reply to Luis Omar Moran
    Expert 2920 points
    Dear Luis,

    Thank you for the reply.

    Things are getting a little clearer but there is still one thing that is not so clear to me about the HD3SS3220 which I was trying to ask in my previous reply.

    " since the HD3SS3220 is a passive switch and does not deal with the information on the SS lanes." Does this mean that the signals that are input into the HD3SS3220 will be output without any swapping of polarity ? e.g a signal (e.g. a negative signal) is routed to pin 17 then it will be output from HD3SS3220 on pin 6 with no swapping of polarities within the HD3SS3220 ? If this is true I you might want to clarify this a little within the data sheets for the HD3SS3220 ?!

    Best regards

    Shmuel
  • 0 in reply to Shmuel Davis
    TI__Genius 16150 points

    Hi Shmuel,

    According your statement: ." Does this mean that the signals that are input into the HD3SS3220 will be output without any swapping of polarity ?

    The answer is yes, as I mentioned before the compensation of the polarity is performed by the receiver (compliant with USB3.x), basically the receiver shall use the D10.2/21.5 symbol within the TSEQ Ordered Set to determine lane polarity inversion for Gen1 for Gen2 the receiver shall use the SYNC Ordered Set and symbols 2, 4, 6, 8, 12 and 14). This is according to the USB3 specification, our devices are compliant with USB spec.

    Best Regards,

    Luis Omar Moran

    High Speed Interface

    SWAT Team