Altera Cyclone II PowerPlay Early Power Estimator - Manual (Page 45)

Altera Corporation 3–29
May 2006 PowerPlay Early Power Estimator User Guide For Cyclone II FPGAs
Using the Cyclone II PowerPlay Early Power Estimator
If you are using a low, medium, or high profile heat sink, select the airflow
from the options of still air and air flow rates of 100 lfm (0.05 m/s), 200
lfm (1.0 m/s), and 400 lfm (2.0 m/s). If you are using a custom heat sink,
enter the heat sink-to-ambient thermal resistance (
θ
SA
). The airflow
should also be incorporated into
θ
SA
. Therefore, the Airflow parameter is
not applicable in this case. Obtain these values from the heat sink
manufacturer.
The ambient temperature does not change, but the junction temperature
changes depending on the thermal properties. Since a change in junction
temperature affects the thermal device properties used to calculate
junction temperature, calculating junction temperature is an iterative
process.
The total power is calculated based on the device properties which
provide
θ
JA
,
θ
JB
, and the ambient, board and junction temperature using
the following equation:
Figure 3–26 shows the thermal analysis, including the junction
temperature (T
J
), total θ
JA
, θ
JB
, and the maximum allowed T
A
values. For
details on the values of the thermal parameters not listed, click Details.
Figure 3–26. Thermal Analysis in the PowerPlay Early Power Estimator
Spreadsheet
(T
J
– T
A
)
θ
JA
(T
J
– T
B
)
θ
JB
+ P =