Dynamic power question

[deepa187]

Hi,

I want to estimate the dynamic power with given voltage and frequency. I know the formula for that is cV^2f.

If V is given 4 volts and f is given 800 MHZ. How do I calculate the dynamic power (estimation) in watts?

Regards,
deep

 

[Idontcare]

Welcome to the forums deepa187!

See this thread here for some discussion on that topic

If you are solely interested in the dynamic power, ignoring the temperature-dependent static-power, then you need a way of estimating the capacitance of the IC in question (the variable "c" in your posted equation)...and be aware that capacitance is application dependent as it depends on the specific suite of instructions being called upon during the calculations.

If your processor happens to be a quad-core sandy-bridge or quad-core ivy-bridge then the effective capacitance happens to be known (for the application is Intel's BurnTest) then you are in luck as I have experimentally arrived at the following capacitance for those two specific processors:

(answer: approximately "15" for both)

 

[TuxDave]

At 15nF for dynamic capacitance, 4V @ 800MHz = The maximum power delivered by your power supply before fuses blow since the Ivybridge transistors would probably short out.

 

[deepa187]

Hi,

Many Thanks for quick response.

P(dynamic) = c* 4*4(volts)*0.8(GHZ)

What is unit of capacitance here? is it nF?

if it is, so I will give me results in watts? Please correct me if I am wrong.

Regards,
Deepa

 

[TuxDave]

Hi,

Many Thanks for quick response.

P(dynamic) = c* 4*4(volts)*0.8(GHZ)

What is unit of capacitance here? is it nF?

if it is, so I will give me results in watts? Please correct me if I am wrong.

Regards,
Deepa

Yes, nano to balance the giga in the clock frequency.

 

[Abwx]

Should multiply the terms above by the pulsation 2pi.

Formulae is Pd(V,F,C) = V^2/(1/2pi.FC) = (V^2).(2pi.FC)

F in GHz and C in nanofarads for ease of calculation as pointed by Tuxdave.