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finding leakage power???

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praveen.kumar432

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20% switching,cell count=200k,f=100mb,pcomb(50% of switching)=5nw/Mh,pleakage=4nw

i did not understand 20% switching means what??50% of switching means what??

can any one help to solve ths prob??

thanks
 

pavanks

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I guess 20 percent means 20 percent of ur total cells are switching from 0-1 or 1-0 per second. same for comb logic 50 percent.

I am not sure though.
 

englishdogg

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@praveen.kumar432

I am confused what info your looking forward to...
switching will impact dynamic power and not leakage power
 

jeet_asic

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"Switching" is related to " clock network "which takes high power in an design. If your clock is very fine i.e. edges are very sharp , then it will take more switching power , thats why clock edges aren't kept very sharp . Clock is the main source of power usage , so pcomb (50% of switching) means that combinational power dissiaption is 50% of switching power . so if you want to reduce it , you need to use clock gating technique . basically , sources of dissipation in a CMOS are due to 1) leakage current 2) short circuit current and switching current .

Switching current : Power dissipated in charging capacitive load , also know an dynamic power consumption .


Total power = core power + I/O power

core = standard cells + Macros

In standard cells , clock networks are main source of power consumption.

Correct me if i am wrong.

20% switching,cell count=200k,f=100mb,pcomb(50% of switching)=5nw/Mh,pleakage=4nw

i did not understand 20% switching means what??50% of switching means what??

can any one help to solve ths prob??

thanks
 
Last edited:

nisshith

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in the given q the relevant data to get leakage power is only the last one "pleakege"
multiply it by cell count to get total leakage power in your case answer would be 200k * 4nw= 800uW

rest data is used to calculate the dynamic power.

Switching acivity means the % of cells switching simultaneously at a particular point of time.
 

praveen.kumar432

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Thanks for responce.i want to know how to find the DYNAMIC POWER with that data.In that data %indicates what??
 

nisshith

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to solve for dynamic power is also easy.
Given is the Pcomb for 50% switching = 5nW/MHz
Therefore, Pcomb for 20% switching = 2nW/MHz (simple mathematics)

Now the Dynamic Power = Switching Power = Pcomb (at 20% switching) * frequency * No. of cells = 200k * 100 * 2nW = 40mW
 

praveen.kumar432

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HI nisshith

---------- Post added at 14:11 ---------- Previous post was at 14:06 ----------

HI nisshith
I have a small query regarding power dissipation..generally leakage power always be active if i am calculating the dynamic power shall i include leakage power or not(Ideally befor Vt current should be zero but actual case we have small leakage curnt
)..
 

nisshith

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I order to calculate total power dissipation you always have to include leakage power but as you saw in the example it is very small as compared to dynamic power. Leakage power is mainly used to calculate the power consumption by circuit in stand by mode.
So even if you include Leakage power in calculating total power it will have no significant effect on total power dissipation in most of the cases.
 

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