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TM4C129ENCPDT: USB0VBUS

?? ??
Prodigy 30 points
Part Number: TM4C129ENCPDT


Tool/software:

USB0VBUS is 5V voltage, but can 5V from USB0VBUS flow to VCC (3.3V) line in TM4C129ENCPDT?
When 3.3V voltage is not supplied to VCC, if USB cable is connected and 5V is supplied to USB0VBUS, 3.3V voltage rises to about 0.05V or 1V.
Do you know the cause of the above?

  • 0
    TI__Guru**** 191906 points

    Hi,

    ?? ?? said:
    USB0VBUS is 5V voltage, but can 5V from USB0VBUS flow to VCC (3.3V) line in TM4C129ENCPDT?
    When 3.3V voltage is not supplied to VCC, if USB cable is connected and 5V is supplied to USB0VBUS, 3.3V voltage rises to about 0.05V or 1V.
    Do you know the cause of the above?

    Please refer to the datasheet for details about the limit on the IO pad voltage when the device is unpowered. 

    Also refer to the TM4C129 System Design Guideline for best practice on VBUS signal. A 100ohm series resistor is recommended if you plan to use only in USB Device mode.