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If you do not connect the Vcc and VUSB, problem or occurrence?

da
Expert 2780 points


Hi
In MSP430F55xx, you can drive the MSP430 by supplying to Vcc generates VUSB by LDO from VBUS.
At this time, VBUS to supply, but if it is not connected to Vcc, the problem occur?

  • 0
    Guru 20670 points

    Hi da,

    I'm a bit confused to what your question is.

    I'm guessing you have doubts about the MSP430F55xx launchpad power supply. You can use the USB 5V which will be regulated for the MCU.

    You can also supply 5V or any acceptable voltage for the regulator (i can't remember from the top of my head th range) from another source into the VBUS. If you supply less than 5V into the VBUS it's a good idea do disconnect the programmer side by removing the jumper

    You can also supply 3.3V, or any voltage in the MCU range to the VCC, but remember that is direct into the MCU so be careful 

  • 0 in reply to Luis Afonso
    Expert 2780 points

    Thank you

    Usually, it will be the power supply like this ...
    Case 1
    VBUS = 5v
    VCC = 3.3v

    Case 2
    VBUS = 5v
    VCC = VUSB (3.3v)

    Case 3
    VBUS = OFF
    VCC = 3.3v


    Do problem will occur when held in this state?
    ( MSP430 does not run in this state )
    VBUS = 5v
    VCC = OFF (0v)


    Regards

  • 0 in reply to da
    Guru 20670 points

    Hi,

    The MSP430 simply won't be powered. Everything will run fine, when you try to program of course it will give you a error since there isn't any MSP430 connected.

  • 0 in reply to Luis Afonso
    Expert 2780 points

    I'm sorry, It is not a program.

    The method of the supply of a power supply to MSP430F55x is as follows.

    Case 1
    VBUS(5v) power supply is connected to VBUS pin.
    Vcc(3.3v) power supply is supplied to a DVCC pin.

    Case 2
    VBUS(5v) power supply is supplied to a VBUS pin.
    VUSB pin is connected to a DVCC pin.

    Case 3
    VBUS power supply is connected to a ground.
    Vcc(3.3v) power supply is connected to a DVCC pin.

    Case X
    VBUS power supply is connected to a VBUS pin.
    DVcc pin is open.

    When you connect only VBUS, is not connected to Vcc, and wanted to know MSP430F55xx whether from being destroyed.

    > The MSP430 simply won't be powered.

    May I take a MSP430 for the purpose of not breaking?

    Regards.

     

     

     

  • 0 in reply to da
    Guru 227245 points

    The supply rails for the PHY (the physical USB layer) and the MSP are completely independent. One can be powered while the other isn’t. Usually, you use VBUS to source the included LDO voltage regulator to get the MSP supply voltage. So MSP is powered when VBUS is there. However, this is not a must. You can also use an ‘ideal ORing diode’ to power the MSP from VBUS if present and from a different supply, if not. (on some MSPs, you have a backup supply that can do this switch automatically)

  • 0 in reply to da
    Intellectual 645 points

    I think da is trying to ask: Will the MSP be damaged or not if we connect VBUS pin of MSP to 5V power source while DVCC pins are unpowered.

    Generally we should not apply power to any IO pin of the MCU when it is not supplied power. But it may be different this case of VBUS pin?

  • 0 in reply to Tuan Pham
    Expert 2780 points

    Hi


    VBUS is not a GPIO.

    Power supply pin.

     

    <MSP430F55xx>

    VBUS : USB LDO input (connect to USB power source) : TYP 5.0v

    VUSB : USB LDO output TYP 3.3v

     

     

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