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TUSB8041: PWRCTL Polarity wrong ?

Christian Ostermeier
Prodigy 20 points
Part Number: TUSB8041

Hello.

The data sheet describes quite clearly that the PWRCTL_POL pin must be pulled high to control Active High peripherals.

For security reasons I even have an additional 10k pullup to PWRCTL_POL.

When the linux kernel tries to activate the hub power, the port stays powerless.

After i tell uhubctl to turn off the power

uhubctl -a off -n 0451 -p 1 -R

The port gets powered on.

Is this a software or a hardware problem ?

  • 0
    TI__Guru 60870 points

    Hi Christian,

    The hub power control outputs will be active high when PWRCTL_POL is pulled high.

    Please note when USB_VBUS is high,  the hub will not turn on downstream port power until the host sends the appropriate USB commands to do so.  If battery charging is enabled on the downstream ports (pullup on PWRCTLx/BATENx or through the hub register) then downstream port power is enabled when USB_VBUS is low, then toggles low when USB_VBUS goes high and waits until the host sends the appropriate USB commands.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 20 points

    It works. If i remove my external pullup and rely on the internal one.

    Whats wrong here ? Is pulling UP not allowed ?

  • 0 in reply to Christian Ostermeier
    TI__Guru 60870 points

    Hi Christian,

    Can you probe the pin at power on?  I'm not having any trouble adding a pullup on the EVM.

    Regards,

    JMMN