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USB Hub LED indicator?

Binh Thai
Expert 1320 points
Other Parts Discussed in Thread: TUSB2077A

Please refer to page 4 in the datasheet of the TUSB2077A 7-port USB Hub controller. (

http://focus.ti.com/lit/ds/symlink/tusb2077a.pdf) The document says "When any port is powered on, PORTPWR is high...". How is it related to the connection of a USB device? Does the pin only go high when there's a USB device connected? Does it go high before or after the enumeration of the USB device?

Thanks a lot.

Binh

  • 0
    TI__Guru 60870 points

    If the TUSB2077A implements power management then the PORTPWR pin(s) will be high whenever port power is enabled by the USB host.   The PORTPWR is not dependent on having a downstream device installed.  Typically a USB host will turn on the port power once the hub is enumerated.