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TUSB2077 downstream power enable question

Andy Eadie
Prodigy 10 points

I would like to know exactly what the TUSB2077 checks for before enabling the downstream port power (/PWR_ON). Is it looking for enumeration with the host PC? I’m looking for a way of making the hub enable the downstream port power without the unit being plugged into a host PC.

Thanks.

  • 0
    TI__Guru 60870 points

    The TUSB2077 will wait for a SetPortFeature(PORT POWER) command from the USB host prior to activating any of the PWRON/ outputs.  These types of commands are sent as part of USB enumeration.  If you want to create a self powered hub that always powers the downstream ports you will not be able to use the PWRON/ outputs to directly control the downstream port power switches.

  • 0 in reply to JMMN
    Prodigy 20 points

    related to the same topic, I have another doubt:

    in ganged mode, do I have to tie all de /pwron ports together (like OCUR pins) in order to control the downstream power?

    Or, in ganged mode /pwron ports remain independent?, this way if I want to power downstream port 2, as example, I have to control it with /pwron2?.

    I have an application with a self powered hub (TUSB2077) and 4 downstream ports, but only one of them is active because others are for backup only, just in case of failure of active port, and the power is applied to all ports connectors at the same time (one common control), but always there is only one physical downstream conection.