1. Home
  2. Hobby Electronics Basics
  3. Measuring Power Consumption of Processor

Measuring Power Consumption of Processor

Hi,

question about basics of power measurement...

In the power equation, we have

1) static power by = I X Vdd [static] 2) switching power = 0.5 X C X (Vdd^2) X f [dynamic] 3) short circuit power = Q X vdd X f X N [dynamic] 4) leakage power = I(leak) X Vdd [static]

How do we measure these components?

-For finding static power, we find total current flowing (from voltage drop across register). and Multiply it by Supply voltage (core voltage). right?

-How do we measure switching power of processor assuming maximum switching activity? we know f and Vdd. What about C ?

-How do we measure short circuit power ?

-Can we disable clock to find leakage power component of static power?

Thanks, Nilesh

Reply to
Nilesh Khambekar
Loading thread data ...

1.0, not 0.5. Every clock has two edges.

John

Reply to
John Larkin

Does not, the bucket fill on the positive edge, using the top FET?. Bucket contents dumped on neg edge. regards john

Reply to
john jardine

"john jardine" a écrit dans le message de news:cnj9tr$pud$ snipped-for-privacy@newsg1.svr.pol.co.uk...

Sure, but... 1/2 C V^2 is just the energy stored into the capacitor and doesn't account for the energy wasted into the switches.

For a cap charged from a supply U :

Wu = U int(i*dt)

and also U = int(i/C*dt)

which gives Wu = C U^2.

So, 1/2 C U^2 dissipated into the CPU at the rising edge, and the same at the falling edge.

--
Thanks,
Fred.
Reply to
Fred Bartoli

Hi,

Thanks.

Let me pinpoint my question... What is practical procedure to measure these power components ?

1) How do I get C for finding switching power ? 2) How do I get I(leak) to meaure short circuit power 3) How can one measure leakage power

thanks, Nilesh

Reply to
Nilesh Khambekar

Measure the slope of the Icc-versus-Fclock curve. Or look for it on a datasheet, where it's sometimes specified. Note that "dynamic power capacitance" isn't always real capacitance, as it may include significant shoot-through current spikes.

Short circuit power is zero.

Measure Icc at zero clock frequency. Multiply by Vcc.

John

Reply to
John Larkin

Bucket

Thanks Fred. I'd come in from a simple SMPS 'transfer of energy' POV, assuming zero switch losses and neglecting that it needs the averaged work to charge the cap (*0.5) and then averaged work to discharge it (*0.5). regards john

Reply to
john jardine

Hi,

Thanks!

Can you suggest some useful book related to this topic? Or some good online references?

This will help me doing the actual measurements.

Basically I am CS student having some work experience in embedded systems.

again thanks, Nilesh

Reply to
Nilesh Khambekar

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.