Altera PowerPlay Early Power Estimator Manuel d'utilisateur télécharger pdf (Page 39)

Chapter 3: Using Cyclone III PowerPlay Early Power Estimator 3–27

Factors Affecting PowerPlay Early Power Estimator Accuracy

When placing the heat sink on the FPGA, the direction of the fins must correspond

with the direction of the airflow. The top view shows the correct orientation of the fins

(

Figure 3–24).

These considerations can heavily influence the airflow seen at the device. When

entering information into the PowerPlay Early Power Estimator, you must consider

these implications in order to get an accurate airflow value. You must determine the

actual airflow at the FPGA and correctly input this value into the PowerPlay Early

Power Estimator.

Temperature

The PowerPlay Early Power Estimator requires you to enter the ambient air

temperature for the device in order to calculate the thermal information of device

correctly. Ambient temperature refers to the temperature of the air around the device.

This is almost always much higher than the ambient temperature outside of the

system. To get an accurate representation of ambient temperature for the device, the

temperature must be measured as close to the device as possible. This can be done

with a thermocouple.

Entering an incorrect ambient air temperature can drastically alter the power

estimates in the PowerPlay Early Power Estimator.

Figure 3–25 illustrates a simple system with the FPGA housed in a box. In this case,

the temperature is very different at each of the numbered locations.

Figure 3–24. Heat Sink (Top View)

Heat Sink Fins

Figure 3–25. Temperature Variances

FPGA

1 2 ... 34 35 36 37 38 39 40 41 42

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Altera PowerPlay Early Power Estimator Manuel d'utilisateur Page 39