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Original question:

TUSB320: VCONN

TUSB320HAI: tDRP fluctuation

Shota Mago
Expert 7150 points
Part Number: TUSB320HAI
Other Parts Discussed in Thread: TUSB320, TUSB322I, TUSB320LAI

Hi team,

My customer considers to use TUSB320/HAI/LAI and provided some questinos.

  1. The data sheet shows its tDRP is 50~100ms.
    Does tDRP cycle of same individual device fluctuate like "60ms cycle, then 70ms"(not device to device variation but fluctuation of device itself)?
  2. Some of CC controller which doesn't supply VCONN doesn't connect when active cable is detected.
    Does TUSB320 family can connect successfully even if active cable is connected?

Best regards,

Shota Mago

  • 0
    TI__Guru 64326 points

    Hi Shota,

    1. DRP duty cycle should not fluctuate by a large amount unless DRP_DUTY_CYCLE is being changed through I2C or Try.SNK/SRC is enabled.  

    2. If active cables are to be supported then TUSB322I should be used as it supports Vconn. 

  • 0 in reply to Malik Barton57
    TI__Expert 7150 points

    Hi Malik,

    Thanks for your quick reply.

    As for question #2, the customer actually will not support active cable at their product. That's why they consider to use TUSB320.  But there is some possibility that end user might connect active cable and they would like to make sure what if active cable is connected to TUSB320.

    Could you please answer question #2 in case of TUSB320?

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru 64326 points

    Hi Shota,

    I would expect that no connection would be made or ,at best, only USB 2 would connect. Since Vconn is not present re-drivers internal to the cable will not be powered. This would be the case for TUSB320 or any other CC controller that does not support Vconn.

  • 0 in reply to Malik Barton57
    TI__Expert 7150 points

    Hi Malik,

    Thanks for your answer.

    Let me ask you about tDRP a bit more detail.

    Does Try.SNK/SRC of TUSB320 fluctuate period and duty of  DRP?

    [Background]

    My customer's understanding is that the effect of Try.SNK/SRC will be active after once the DRPs have established a connection with each other.

    He's concerned that when DRP devices are connected to each other, if the tDRP and duty are the same, the source/sink relationship is not permanently established.(Though it might be extremely rare case)

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru 64326 points

    Hi Shota,

    When two DRP devices are connected that do not implement Try.SNK/SRC then there will be a race condition for which device starts DRP advertisement (toggle) first. The device that starts first will soon present R.p when the other port enters Unattached.SNK starting the process for valddating connection. I have not seen issues where timing matches perfectly and creates an infinite loop. 

    Try.SRC/SNK modulate the first attempt at advertisement such that RP o RD is exposed for a long time. This will allow the other port to detect a stable Rp or Rd before toggle starts. Hopefully that is clear.

  • 0 in reply to Malik Barton57
    TI__Expert 7150 points

    Hi Malik,

    Thanks for your detailed explanation.

    Let me ask your answer.

    Does the USB320LAI's Try.SNK include a function to widen the Rd presentation interval (Duty) in addition to the standard Try.SNK operation?

    In that case, does it mean that the value set in "DRP_DUTY_CYCLE" is ignored?

    Also, let me ask you more detail about connection with active cable and TUSB320LAI.

    Whether it is an active cable or an e-marked cable, from CC controller side,  it will see like Ra/Open or Ra/Rd is connected to CC1/CC2 respectively.

    Upon detection of this resistor combination, does TUSB320LAI try to disconnect CC pin proactively?

    Some of other maker's CC controller behave like above.

    The customer thinks this resistor combination is defined by standard, so behavior of CC controller would be nothing to do with specification of active/E-marked cable.

    I would appreciate your kind support.

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru 64326 points

    Hi Shota,

    TUSB320LAI Try.SNK functionality is a device state. While in the Try.SNK state Rd is presented on both CC1/2 for tDRPTryWait (400 ms - 800 ms). Once it is exited then DRP toggle will commence at the specific duty cycle configured in DRP_DUTY_CYCLE.

    If TUSB320LAI is presenting Rd it will actively polling for Source (DFP) termination. In the presence of Ra, Rd will still remain connected and TUSB320LAI sees SNK.Open. During DRP toggle, Ra can be detected when DFP termination is present and ACTIVE_CABLE_DETECTION bit will be set.