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TUSB4020BI-Q1: Insertion Loss Inquiry

Evan Wang
Genius 9770 points
Part Number: TUSB4020BI-Q1
Other Parts Discussed in Thread: TUSB211A

Tool/software:

Hi Team,

1. Could you help to clarify the insertion loss of the TUSB4020BI-Q1?

Datasheet didn't mention about the dB loss of USB2 signal.

2. Do we have any IBIS model for this IC? Can't find it on ti.com.

3. Is there any requirement for the insertion loss from USB HUB to connector?

Thank you.

  • 0
    TI__Guru*** 146940 points

    Hi Evan:

       Insertion loss is for S-parameter model, which is normally used for mux or PCB simulation. Hub is retimer, S-parameter mode can not used for retimer simulation.

      Unfortunately,  we don't have  IBIS model for TUSB4020B .

    Best

    Brian

  • 0 in reply to Brian Zhou
    TI__Genius 9770 points

    Hi Brian,

    Since the TUSB4020BI-Q1 is a HUB, how to evaluate the signal loss because of it? or like you mention that since HUB is Re-timer so we can ignore the loss of it?

    And if TUSB4020BI-Q1 is act as a retimer, do we still need to place it close to the USB2 connector?

    Do we have any limitation on the distance between HOST <-> TUSB4020BI-Q1 <-> Connector?

    From "USB 2.0 Board Design and Layout Guidelines", it says "DP/DM traces should always be matched lengths and must be no more than 4 inches in length;". But datasheet says "Eight inches is the maximum recommended trace length for USB 2.0 differential-pair signals".

    Could you help to clarify this part? since it's also related to where should we place the TUSB4020BI-Q1

  • 0 in reply to Evan Wang
    TI__Guru*** 146940 points

    Hi  Evan:

        Where did you see  USB 2.0 Board Design and Layout Guidelines?

        TI hub datasheet recommended 8 in trace length from host to hub  upstream port  and hub downstream port  to USB connector  is based on USB2  HS eyediagram  data from TI hub test. So make sure trace length  on both sides of hub do not exceed 8in Fr4 trace. if more than 8ic, an USB2 redriver may needed, like TI USB2 redriver TUSB211A.

    Best

    Brian

        

  • 0 in reply to Brian Zhou
    TI__Genius 9770 points

    Hi Brian,

    FYI.

    That's why I'm confused about it...

    Perhaps the total 8 inches refer to HOST-> 4 inches -> HUB-> 4 inches -> Connector since Hub act as a retimer?

    8 inches refer to the entire USB2 path right?

    USB 2.0 Board Design and Layout Guidelines (1).pdf

  • 0 in reply to Evan Wang
    TI__Guru*** 146940 points

    no,  8 in is from host to   hub upstream port  or hub downstream port to USB connector.

    Best

    Brian