Altera PowerPlay Early Power Estimator for Altera CPLDs - Manual (Page 23)

Chapter 2: PowerPlay Early Power Estimator Worksheets 2–13
Factors Affecting the PowerPlay Early Power Estimator Spreadsheet Accuracy
December 2010 Altera Corporation PowerPlay Early Power Estimator for Altera CPLDs User Guide
Factors Affecting the PowerPlay Early Power Estimator Spreadsheet
Accuracy
There are many factors that affect the estimated values displayed in the PowerPlay
EPE spreadsheet. In particular, the input parameters entered concerning toggle rates,
airflow, and temperature must be accurate to ensure that the system is modeled
correctly in the PowerPlay EPE spreadsheet.
Toggle Rate
The toggle rates specified in the PowerPlay EPE spreadsheet can have a large impact
on the dynamic power consumption displayed. To obtain an accurate estimate, you
must input toggle rates that are realistic. Determining realistic toggle rates requires
you to know what kind of input the CPLD is receiving and how often it toggles.
To get an accurate estimate even if the design is not complete, isolate the separate
modules in the design by functionality and estimate the resource usage along with the
toggle rates of the resources. The easiest way to accomplish this is to leverage
previous designs to estimate the toggle rates for modules with similar functionality.
The input data in Figure 2–12 is encoded for data transmission and has a roughly 50%
toggle rate.
In this case, you must estimate the following:
■ Data toggle rate
■ Mod input toggle rate
■ Resource estimate for the Decoder module, RAM, Filter, Modulator, and Encoder
■ Toggle rate for the Decoder module, RAM, Filter, Modulator, and Encoder
You can generate these estimates in many ways. If you used similar modules in the
past with data inputs of roughly the same toggle rate, you can leverage that
information. If there are MATLAB simulations available for some blocks, you can
obtain the toggle rate information. If the HDL is available for some of the modules,
you can simulate them.
If the HDL is complete, the best way to determine toggle rate is to simulate the design.
The accuracy of toggle rate estimates depends on the accuracy of the input vectors.
Therefore, determining whether or not the simulation coverage is high gives you a
good estimate of how accurate the toggle rate information is.
Figure 2–12. Decoder and Encoder Block Diagram
Decoder RAM Filter Modulator Encoder
Mod Input
Data