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Altera_Forum's avatar
Altera_Forum
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14 years ago

A question about the powerplay power analyzer tool

I used power analyzer tool estimate a vcd fire, the result is nearly 67mw. Since I insert a resistor in the power supply rail of the FPGA core, and I measure that the current flow into the FPGA core is nearly 12mA. Because the power supply of the FPGA core is 1.2V in theory, so the measured power consumption is about 14.4mW when I run the test program (same with vcd file). My question is why the result get from the power analyzer tool is so larger than the result I measured? Thank you very much!

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    Basically powerplay is using four items to come up with the number.

    Toggle Rate, (typically defaults to 12.5%, but in your case you are using a VCD file).

    Temperature, (Takes worse case corner, normally hot.)

    Voltage Skew, (Probably takes worse case corner, high)

    Die Lot Skew (again takes worse case corner).

    All of these things have a significant effect on the total power of the device, and the worse case can have a significant impact on the power draw. The purpose of the tool is to give you a "Worse Case" design target.

    If you take your existing design, and increase the temperature to 70C you should see a significant difference in the current draw.

    The Die Skew is something that you won't be able to control, and your particular devices is probably not on the worse case corner, but is something you still need to take into account when designing your board.