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TUSB1142: Specification and ACTIVE cables

Orlando Sosa
Prodigy 10 points
Part Number: TUSB1142

Tool/software:

Hi -
We are exploring the use of the TUSB1142 and it's Adaptive Equalization capabilities. However, in reading the TUSB1142 data sheet, we see that there is a note that "AEQ should never be enabled in an active cable application".
 
QUESTIONS:
-A- is this referring to:
    (1) not using the TUSB1142 AEQ feature for a device which is inside an active cable?
or (2) a system (like or product) that may connect to an active cable? 
-B- assuming option (2) is the answer, we plan to use in a product that will look to behave as a dual-role data (DRD) port. As such, when our USB-3 product connects to a host and functions as UFP, the VCONN source is from host/DFP. The concern is that we understand that in this environment, only the host can talk to the cable to determine how it's identified  (passive, active, optic, hub, etc). In this scenario, there seems to be no mechanisms that allow for our product to discover the cable information in order to disable AEQ for active cable.
Thanks,
-OSOSA
  • Intellectual 280 points

    Would like to further elaborate:

    C) wonder on the '1142's DataSheet statement that "The TUSB1142 is intended to reside between a Host and a USB-C receptacle or between a USB device and a USB-C receptacle.".  Any idea on what the exact meaning of "or "?  Does it mean only one or the other can have it or that it can be present on both?  If only one is allowed will then mayhem ensue if both Host and Device are endowed with it?

  • in reply to Georg Mussenden
    TI__Guru**** 178126 points

    Hi,

    Georg Mussenden said:
    "The TUSB1142 is intended to reside between a Host and a USB-C receptacle or between a USB device and a USB-C receptacle.".

    For this statement, it means you can design in TUSB1142 either in a source side application or a sink side application. You can use a source with TUSB1142 and a sink with TUSB1142, and as long as both the source and sink are USB3x compliant, then the source will work with the sink. 

    But TUSB1142 is not expected to be designed in an active cable application.

    Thanks

    David 

  • in reply to David (ASIC) Liu
    Prodigy 10 points

    Hello David - 

    To be sure I'm clear...returning to my original question, the spec calls out that the TUSB1142 AEQ (Adaptive Equalization) "should never be enabled in an active cable application". Additionally, you pointed out that it is "not expected to be designed in an active cable application". We are not evaluating this for designing into an active cable application.  However, we can not control what type of cable would be connected to our product, where we hope to have the TUSB1142 AEQ enabled.

    Is there a problem with our target use case? In other words, if our product uses the TUSB1142 with the AEQ enabled,

    • it can (will work),
    • or can it not have (won't work)

    if an active cable is connected to it be a user?

    Thank you

  • in reply to Orlando Sosa
    TI__Genius 11480 points

    Hi, 

    To help clarify, the Adaptive EQ feature is meant to be enabled only on the connector facing interface of a Host or Device implementation, the channel between the Host/Device and redriver would have a fixed loss and therefore does not have Adaptive equalization. 

    The statement in the datasheet is referring to using the redriver in an active cable application where adaptive EQ should not be used.

    Sounds like your case is what this redriver is designed to support, a fixed amount of loss between the Host/Device and TUSB1142, and unknown amount of loss at the connector where the adaptive equalization feature is used.

  • in reply to Undrea Fields
    Prodigy 10 points

    Thank you Undrea Fields -

    You are correct about our design case... it was just unclear if "an active cable application meant:

    1. "a design (application) where the TUSB1142 using AEQ was within the cable itself" ... should NOT use AEQ
    2. or a "system-level (application)" that would include our device potentially connected to an active cable (to a host PC for example)... can use AEQ

    Again, thank you for the feedback / clarification. I tend to agree w/ your interpretation which would be option (1) above.

  • in reply to Orlando Sosa
    TI__Guru**** 178126 points

    Hi,

    Your (1) interpretation is correct

    1. "a design (application) where the TUSB1142 using AEQ was within the cable itself" ... should NOT use AEQ

    Thanks

    David