Altera PowerPlay Early Power Estimator User Manual
Page 14
Input Parameter
Description
Junction Temp, T
J
(°C)
Enter the junction temperature of the device. This field is only
available if you turn on the User Entered T
J
option. In this case,
the junction temperature is not calculated based on the thermal
information provided.
For Enpirion power device selection, Altera recommends setting
Junction Temp, T
J
(°C) to the highest value for the chosen
temperature grade.
Ambient Temp, T
A
(°C)
Enter the air temperature near the device. This value can range
from –40°C to 125°C. This field is only available when you turn
on the Auto Computed T
J
option.
If you turn on the Estimated Theta J
A
option, this field is used to
compute the junction temperature based on power dissipation and
thermal resistance through the top-side cooling solution (heat sink
or none) and board (if applicable).
If you turn on the Custom Theta J
A
option, this field is used to
compute junction temperature based on power dissipation and
custom θ
JA
entered.
Heat Sink
Select the heat sink that is used. You can select one of the
following:
• No heat sink (None)
• A custom solution (Custom)
• A heat sink with set parameters (15 mm–Low Profile, 23 mm–
Medium Profile, or 28 mm–High Profile). This field is only
available if you turn on the Auto Computed T
J
and Estimated
Theta J
A
options.
If you select None, the heat sink selection updates the custom θ
SA
value and you can see the value in the Custom θ
SA
(°C/W)
parameter. If you select Custom, the value is what is entered in the
Custom θ
SA
(°C/W) parameter.
Representative examples of heat sinks are provided. Larger heat
sinks provide lower thermal resistance and lower the junction
temperature. If the heat sink is known, consult the heat sink
datasheet and enter a custom θ
SA
value according to the airflow in
your system.
Airflow
Select an available ambient airflow in linear-feet per minute (lfm)
or meters per second (m/s). The values 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 if you turn on the Auto Computed T
J
and Estimated
Theta J
A
options.
Increased airflow results in a lower case-to-air thermal resistance
and lowers the junction temperature.
3-4
Input Parameter
UG-01070
2015.01.20
Altera Corporation
PowerPlay Early Power Estimator Worksheets