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C6655 power spreadsheet, why is the CPU frequency limited to not go below 800MHz?

Brad Caldwell
Genius 12595 points

I'm looking at the C6655 power estimation spreadsheet (sprm601.zip). I'd like to run the processor slower than 800MHz via PLL settings to save on power. The spreadsheet doesn't let me enter anything below 800MHz. What is the reason for this constraint? Is there a good way to extrapolate?

Thanks

  • 0
    TI__Expert 6815 points

    Brad,

    Unforuntately the lower limit was fixed at 800MHz when it was created back in 1Q13.

    There is a quick and dirty way to extrapolate with reasonable accuracy.

    1) Take the total power reading at a minimum of three CPU frequencies.

    2) Form a slope-intercept equation = a * cpuF + b. (a represents dynamic power, b = static power)

    3) Substitute your desired cpu frequency in 2).

    Starting with Hawking (released yesterday on ti.com) we support frequencies down to 50MHz.