Altera PowerPlay Early Power Estimator - Manual (Page 56)

Figure 4-6: Temperature Variances
FAN
1
2
3
4
FPGA
For example, location 3 is where the ambient temperature pertaining to the device should be obtained for
input into the PowerPlay EPE spreadsheet. Locations 1 and 2 are cooler than location 3 and location 4 is
likely close to 25 °C if the ambient temperature outside the box is 25 °C. Temperatures close to devices in
a system are often in the neighborhood of 50–60 °C but the values can vary significantly. To obtain
accurate power estimates from the PowerPlay EPE spreadsheet, you must get a realistic estimate of the
ambient temperature near the FPGA device.
Heat Sink
The following equations show how to determine power when using a heat sink.
Figure 4-7: Total Power
Figure 4-8: Junction–to–Ambient Thermal Resistance
θJA TOP = θJC+ θCS + θSA
You can obtain the θ
JC
value that is specific to the FPGA from the data sheet. The θ
CS
value refers to the
material that binds the heat sink to the FPGA and is approximated to be 0.1 °C/W. You can obtain the θ
SA
value from the manufacturer of the heat sink. Ensure that you obtain this value for the right conditions for
the FPGA which include analyzing the correct heat sink information at the appropriate airflow at the
device.
4-4 Heat Sink
UG-01070
2015.01.20
Altera Corporation Factors Affecting the PowerPlay Early Power Estimator Spreadsheet Accuracy
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