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Original question:

TIDA-01226: Confusion about the reference schematic——USB bridge circuit

TIDA-01226: Confusion about the reference schematic—— the purpose of U22

user5309454
Intellectual 420 points
Part Number: TIDA-01226

Hi

Is the purpose of designing the U22 to power external devices via the USB interface?
Best Wishes !
JingMingJun

  • 0
    TI__Mastermind 20045 points
    Hello JingMingJun,

    U22 creates DDCPWR which is used to power the 5V to the ITE6801 IC. This IC is used for the HDMI port.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    Intellectual 420 points

    Hello kyle

    Thank you for your reply.
    In the reference schematic, “DDCPWR” is connected to the output pin of U22, the “R0PWR5V” pin of IT6801 and the “+5V POWER” pin of HDMI interface.
    The "R0PWR5V" pin of the IT6801 is described in the datasheet as "TMDS transmitter detection for Port 0 (5V-tolerant)".
    When the HDMI input signal is connected,
    ①The “+5V POWER” pin of the HDMI interface will become +5V, and it seems that U22 has no meaning.
    ②If the “+5V POWER” pin of the HDMI interface does not have a +5V input, the U22 output seems to be a substitute. But there are two questions:
    Question 1: When there is no "+5V POWER" when the HDMI signal is input, does it exist?
    Question 2: If the situation in Question 1 exists, how does the IT6801 know that there is an HDMI signal input, so that U22 is enabled with the "ENVBUS#" signal?
    Best Wishes !
    JingMingJun
  • 0 in reply to user5309454
    TI__Expert 4610 points
    HI JingMingJun,

    As i mentioned in other thread also.. MSP430 code for this ITE card is not maintain by us.. so we do not have full understanding of the register spec for these pins. I will ask them and can give you the information latter.

    But what I think this is being used for supporting the MHL mode. MHL requires to charge the device which means we have to provide additional power to the connected device (but I am not sure about that).

    The HDMI detection is being done by the Hot_Plug detect pin.

    Thanks,
    Navneet
  • 0 in reply to Navneet Singh
    Intellectual 420 points

    Hi Navneet

    Thank you for your reply.

    If there is any further information, please let me know.
    Thank you very much.
    JingMingJun
  • 0 in reply to user5309454
    TI__Expert 4610 points
    Hi JingMingJun,

    Sure i am in contact with the team and surely shared the information with you once i get it.

    I am sending you the friend request on e2e, please add me there for further communication.

    Thanks,
    Navneet
  • 0 in reply to Navneet Singh
    Intellectual 420 points
    Hi Navneet
    Thank you very much.
    My vacation has just ended and I am very happy to be your friend on E2E.
    Thanks,
    JingMingJun