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TSB2077A in Bus Powered mode

Sree C
Prodigy 180 points
Other Parts Discussed in Thread: TUSB2077A

Hi,


We have been designing a 7-port USB Hub to support high current requirements at down stream. But i could see from TUSB2077A EVM user guide section 4.1 that in Bus Power mode it can only support up to 4 downstream ports & if we want to use more down stream ports then we should also use Wall Wart ( DC Jack). Is that true? I am attaching our schematic for this purpose. Can you please give me some suggestions on this. In between we are designing to support 2A for 4 of the down stream ports and other ports are with lower current support.

Thanks

SreeTUSB 2077A.PDF

  • 0
    TI__Genius 9315 points
    Hi Sree,

    Yes that's true, if you want to use all 7 downstream port you will need to connect a DC adapter.
    In customer's design if needed 7 ports it will have to be configured as Self-Powered since Bus-Powered mode supports only 4 ports.

    Regards.
    JC
  • 0 in reply to Jose Carlos Gil
    Prodigy 180 points
    JC,

    Thank you for your reply.
    in addition the high current ports are capable of 2A for which we are designing. My assumption is that anyhow in our use case at any point of time if we have less than 4 down stream ports in use then i think without the use of DC Jack will suffice. Is that true?pls confirm.

    Thanks

    Srikanth

  • 0 in reply to Sree C
    TI__Genius 9315 points
    Hi Sree,

    If you have less than 4 ports in use at any given time you can go without the DC jack as long as power consumption of downstream ports are lower than the power provided by the upstream port.
    Keep in mind that available power on common USB ports is 500mA.

    Regards.
    JC