KARUNYA_IEEE

7/31/2019 KARUNYA_IEEE

1/15

Accurate Power Measurement

Methodology For VLSI CircuitsUsing CAD Tools

Ajay.G Ramya Rajan

Mtech Student Mtech Student

BNMIT,Bangalore BNMIT,Bangalore

Dr.Veena S Chakravarthi,

Member IEEE,Professor

Department of Electronics & Communication

BNMIT,Bangalore


2/15

Agenda

Introduction

Power

Power Measurement accuracy

Power AnalysisPower measurement using CAD tools

Power measured using Result Browser

Theoretical Power EstimationWhich is Accurate?!

Comparison between the 3 methods

Conclusion6/3/20122


3/15

Introduction

Power plays a critical role in submicron VLSIdesign

The design has to meet the power bugdet.

EDA tools are used to estimate the power of adesign.

The accuracy of Power analysis depends onthe type of algorithms that the power analysistool uses

The proposed method discusses a techniqueto measure the Power more accurately.

6/3/20123


4/15

Power

Power dissipation can be categorizedinto

Static Power dissipation

Dynamic Power dissipation

6/3/20124


5/15

Static power dissipation

The static power dissipates when theinputs are static (either logic 0 or 1)

The static power equation isP(static) =Ids(static) Vds(static) ---(1)

where for saturation condition

Ids(static)=0Cox

((VGS Vth)VDS VDS2/2 )

6/3/20125


6/15

Dynamic Power dissipation

Dynamic power dissipation occurs dueto the switching of the input signals

Dynamic power is given by the

equationP(dynamic)= Ctotal VDD

2 f2

where

= switching activity factor

VDD =Supply voltage

Ctotal= Total capacitance

f = frequency of operation

6/3/20126


7/15

Power Measurement accuracy

In the nanoscale design era the designmust be characterised with greatestaccuracy

Accuracy of a power analysis dependson the algorithm used by the tool

Accuracy plays a significant role wherethe power constraints are critical

In IP based design flow, power is amajor deciding factor and hence needto be accurate

6/3/20127


8/15

Power Analysis

Power Analysis can be done in threeways

Approach 1:Theoretical computations

Approach 2:Using Annotation in CADtools

Approach 3: Using Result browser add-

on

6/3/20128


9/15

Theoretical Power Estimation

In this approach the static current iscalculated by

Ids(static)=0Cox

((VGS Vth)VDS VDS2/2 )

And static power is computed as

P(static) = Ids(static) Vds(static)

6/3/20129


10/15

Power measurement using CAD

toolsApply static inputs to the circuit

Perform simulation using Cadence

SpectreAnnotate the DC conditions

Note the total static current (Is)

Calculate static power using theequation P(static) = IS VDS

6/3/201210


11/15

Power measured using Result

BrowserApply static inputs to the circuit

Opt to save all the results

Perform simulation using CadenceSpectre

Open Result browser add-on

Browse to the power option and notedown the power

6/3/201211


12/15

Which is Accurate?!

It can be observed that there is anerror ranging from -9% to 14.18% inpower estimated using Annotaions.

Where as it is observed that the powerestimate obtained by Result browser ismore accurate with error ranging from-0.3% to 0.99%

The succeding slides will depict theerror in power in relation to theoreticalcomputations

6/3/201212


13/15

Comparison between the 3

methodsPower given by annotating the staticcurrent

Power obtained by Resultbrowser

Accuracy

6/3/201213


14/15

Conclusion

An error in the range of -9% to 14.8%isobserved between the power

measurements by CAD tools andtheoretical computations

An alternative power measurementmethod is to use the Result browser

add-on provided by the vendor andthereby obtain accurate power estimate

6/3/201214


15/15

6/3/201215

Documents

KARUNYA_IEEE