• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 34 subscribers
  • Views 839 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TUSB Connect Detect Pin Behavior

Jake Wegman1
Prodigy 70 points
Other Parts Discussed in Thread: TUSB211

Hello,


I am looking at including the TUSB211 in a design.  I am trying to use this particular part to correct a design error in a product that will be interfacing with this part.  My question relates to the behavior of the CD pin.  I understand that if there is a USB connection, CD will be asserted.  If the peripheral disconnects, it is also my understanding that CD will de-assert.  However, what happens in the situation where the host-side (upstream) data lines disconnect, but VBUS remains.  Will CD also be de-asserted in that particular case?

Thanks,

Jake

  • 0
    TI__Expert 4650 points

    Hi Jake,

    The data sheet Pin Functions Table states that the CD is "asserted from an unconnected state upon detection of DP or DM pull-up resistor. De-asserted upon detection of disconnect." The continued presence of VBUS should not affect the CD de-assertion.

    - Mark

  • 0 in reply to Mark Pieper
    Prodigy 70 points
    Hi Mark,

    Thank you for your quick response. I'm pretty sure that you're telling me what I want to hear, but I want to just make sure I've got this right before I order an eval module. I've included a table of the conditions below and my understanding of the CD state:

    VBUS Present Host Data Lines Connected Peripheral Data Lines Connected CD State
    ------------------ ------------------------------------ -------------------------------------------- ------------
    Yes No No De-asserted
    Yes No Yes De-asserted
    Yes Yes No De-asserted
    Yes Yes Yes Asserted

    I'm assuming it's able to detect this state due to the removal of the pull-downs on the host-side of the interface?

    Thanks,
    Jake
  • 0 in reply to Jake Wegman1
    TI__Mastermind 36085 points
    Hello Jake,

    Your understanding and table are correct, the CD terminal will detect the connection of the device regardless VBUS is always on.

    Regards,
    Diego.
  • 0 in reply to Jake Wegman1
    TI__Expert 4650 points
    Hi Jake,
    I don't think that it will detect disconnected host connections.
    I'll contact you via email to continue this discussion.
    - Mark
  • 0 in reply to Mark Pieper
    TI__Mastermind 36085 points
    Hello Jake & Mark,

    The detection should be the same in both ways (Host & Device), due to the application scheme where the terminals D1P & D1M are shorted with D2P & D2M respectively. Please reffer to the refference schematic (datasheet page 8) and the layout example (datasheet page 12).

    regards,
    Diego.
  • 0 in reply to Diego Cortes
    Prodigy 70 points

    Hello,

    I received the EVM today, and unfortunately it does not detect a host-side connection.  If 5V VBUS is constantly applied, the CD pin will assert once a device is connected, even if the host data lines are not present.

    Thanks,

    Jake