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MSP430FR2433: Active Mode Supply Current

Thomas Foxcroft
Expert 2981 points
Part Number: MSP430FR2433

Sections 5.4 and 5.5 of the data sheet (SLASE59) specify the AM supply current. Why don't the specifications in 5.4 equal to some multiple of Current Per MHz shown in section 5.5?

  • 0
    TI__Genius 17450 points

    The test conditions for 5.5 are different than 5.4 including the cache hit rate, which is an important factor as you can see comparing the 0% and 100%. 

  • 0 in reply to Luke Ledbetter
    Expert 2981 points

    Yes. I saw that.

    I find it misleading that section 5.5 uses a hit rate of 75% instead of 100% as used in section 5.4.

    The numbers just don't add up to me. Maybe it's because 5.4 uses an external clock signal.

  • 0 in reply to Thomas Foxcroft
    TI__Genius 17450 points

    I'll explain a little further here to provide more clarity on to how the numbers were calculated. Keep in mind the test conditions.

    There is always some current that is there, this current could be the b in the linear formula y = mx+b, this could be the leakage current of the system. Now to calculate the slope we had Iam at 8 MHz and Iam at 1 MHz (with 75% cache hit rate for both) then we divided by 7 for the difference. Using the number from 5.4 and the equation from 5.5 we can get the supply current per MHz.

    1 MHz 8MHz Unit
    Iam Current Cache 0%  504 2772 uA
    Iam Current Cache 100%  203 625 uA
    Iam Current Cache 75% 278.25 1161.75 uA
    0% Value(0.25) + 100% Value (0.75)
    Calculated Value
    (Iam 8 MHz - Iam 1 MHz) / 7 126.2143 uA/MHz

    Its important to note that this gives you the slope, but there is also the leakage current and the 75% cache hit rate.

    Regards,

    Luke 

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