Altera PowerPlay Early Power Estimator - Manual (Page 15)

Chapter 3: Using Cyclone III PowerPlay Early Power Estimator 3–3
PowerPlay Early Power Estimator Inputs
© June 2009 Altera Corporation PowerPlay Early Power Estimator User Guide for Cyclone III FPGAs
Figure 3–1 shows the Main section of the PowerPlay Early Power Estimator.
Custom

JA
(°C/W) Enter the junction-to-ambient thermal resistance between the device and ambient air ( o C/W).
This field is only available when you select Auto Computed T
J
and Custom Theta JA.
This field represents the increase between ambient temperature and junction temperature for
every watt of additional power dissipation.
Custom

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 Theta JA, and if you set the Heat Sink parameter to Custom Solution.
The Custom

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.
Board Thermal Model Select the type of board to be used in thermal analysis. The value can either be None
(Conservative), JEDEC (2s2p) or Typical Board. This field is only available when you select
Auto Computed T
J
and Estimated Theta JA.
If None (Conservative) is selected, the thermal model assumes no heat is dissipated through
the board. This results in a pessimistic calculated junction temperature.
If JEDEC (2s2p) is selected, the thermal model assumes the characteristics of the JEDEC 2s2p
test board specified in standard JESD51-9.
If Typical Board is selected, the thermal model assumes the characteristics of a typical
customer board stack, which is based on the selected device and package.
Altera recommends performing a detailed thermal simulation of your system to determine the
final junction temperature. This two-resistor thermal model is for early estimation only.
Table 3–1. Main Section Information (Part 2 of 2)
Input Parameter Description
Figure 3–1. Cyclone III PowerPlay Early Power Estimator Main Section