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MSP430F5438A: If MCLK source from XT2, Is it necessary to adjust the Vcore?

SeaFesse
Expert 2690 points
Part Number: MSP430F5438A


Hello guys,

I want to make sure  If MCLK sourced from XT2 (16MHz), Is it necessary to adjust the Vcore in MSP430F5xxF6xx?

  • 0
    Guru 34773 points

    Per TI datasheet yes, by my experience no.

  • 0
    Guru 318740 points
    Whether you need to adjust Vcore depends only on the clock speed, not on where the clock comes from.
    (Using a too-low Vcore might or might not work; there are no guarantees.)
  • 0 in reply to Clemens Ladisch
    Expert 2690 points

    Hello Clemens,
    Thanks for your reply.
    Yes, adjust Vcore is definitely a no harm measure. but I want to know " why" , why it has no relation to the CLK source.
    In my understanding, DVcc/Vcore afects the frequency of DCO, so If MCLK comes from DCO, a high frequency need a high voltage(power) , that makes sense.
    In fact, my experience is similar to zrno's , Vcore stays in Level0 , CPU runs @16MHz is OK. but it seems different with the user guider.
    so I come  here to look for help.

  • 0 in reply to SeaFesse
    Guru 318740 points
    There is a slight voltage dependence of the DCO, but that has nothing to do with the allowed Vcore ranges.

    Transistors can switch faster if they get more voltage. If Vcore is too low, some transistors might not switch fast enough.
    If you do not increase Vcore for higher frequencies, you are effectively overclocking the chip.

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