Altera PowerPlay Early Power Estimator - Manual (Page 21)

Altera Corporation 3–3
January 2007 PowerPlay Early Power Estimator For Stratix II, Stratix II GX & HardCopy II
Using the PowerPlay Early Power Estimator
Heat Sink Select the heat sink being used. You can specify no heat sink, a custom solution, or
specify a heat sink with set parameters. This field is only available when you select
Auto Compute T
J
and Estimated
θ
JA
.
Representative examples of heat sinks are provided: larger heat sinks provide lower
thermal resistance, and thus lower junction temperature. If the heat sink is known,
consult the datasheet and enter a Custom heatsink-to-ambient value according to the
airflow in your system.
The heat sink selection updates
θ
SA
and the value is seen in the Custom
θ
SA
(°C/W)
parameter. If a custom solution is selected, the value is what is entered for Custom
θ
SA
(°C/W).
Airflow Select an available ambient airflow in linear-feet per minute (lfm) or meters per
second (m/s). The options are 100 lfm (0.5 m/s), 200 lfm (1.0 m/s), 400 lfm (2.0 m/s),
or still air. This field is only available when you select Auto Computed T
J
and
Estimated
θ
JA
.
Increased airflow results in a lower case-to-air thermal resistance, and thus lower
junction temperature.
Custom
θ
JA
(°C/W) Enter the junction-to-ambient thermal resistance between the device and ambient air
(in °C/W). This field is only available when you select Auto Computed T
J
and
Custom
θ
JA
This field represents the increase between ambient temperature and junction
temperature for every Watt of additional power dissipation.
Custom
θ
SA
(°C/W) Enter the heatsink-to-ambient thermal resistance from the heat sink data sheet if you
select a custom heat sink. The quoted values depend on system airflow and may also
depend on thermal power dissipation. This field is only available when you select
Auto Computed T
J ,
Estimated
θ
JA ,
and if you set the Heat Sink parameter to
Custom Solution.
The Custom
θ
SA
parameter is combined with a representative case-to-heatsink
resistance and an Altera-provided junction-to-case resistance to compute overall
junction-to-ambient resistance through the top of the device.
Table 3–1. Main Section Information (Part 2 of 3)
Input Parameter Description