Altera PowerPlay Early Power Estimator - Manual (Page 67)

Altera Corporation 3–49
January 2007 PowerPlay Early Power Estimator For Stratix II, Stratix II GX & HardCopy II
Using the PowerPlay Early Power Estimator
Figure 3–37. Temperature Variances
For example, location 3 is where the ambient temperature pertaining to
the device should be obtained for input into the PowerPlay Early Power
Estimator spreadsheet. Points 1 and 2 are cooler than location 3; location
4 is likely close to 25 degrees C. Temperatures close to devices in a system
are often around 50-60 degrees but the values can vary significantly. In
order to obtain accurate power estimates from the PowerPlay Early
Power Estimator spreadsheet, it is very important to get a realistic
estimate of the ambient temperature near the FPGA device.
Heat Sink
When using a heat sink, the power is determined by the following
equations.
(T
J
- T
A
) /
θ
JA
= P
θ
JA
=
θ
JC
+
θ
CS
+
θ
SA
The value
θ
JC
is specific to the FPGA and can be obtained from the data
sheet. The value
θ
CS
refers to the material that binds the heat sink to the
FPGA and is approximated to be 0.1 C/W. The value
θ
SA
is obtained from
the manufacturer of the heat sink. It is important to ensure that when this
value is obtained that it is for the right conditions for the FPGA which
include analyzing the correct heat sink information at the appropriate
airflow at the device.
For more information on how to determine heat sink information refer to
AN 358: Thermal Management for 90-nm FPGAs and
www.altera.com .
F
A
N
1
2
3
4
FPGA