17–14
Chapter 17: Understanding and Evaluating Power in MAX II Devices
Power Estimation Summary
Thermal Analysis
In the Thermal Analysis part, the PowerPlay Early Power Estimator spreadsheet
considers the device’s ambient temperature and the airflow to determine the junction
temperature (TJ) of the device in °C.
The device can be considered a heat source and the junction temperature is the
temperature at the device. The thermal resistance of the path is referred to as the
junction-to-ambient thermal resistance (θJA). Figure 17–14 shows the thermal model
for the PowerPlay Early Power Estimator spreadsheet.
Figure 17–14. Thermal Model for the PowerPlay Early Power Estimator
Heat Source
Power (P)
T
J
θ
JA
T
A
The PowerPlay Early Power Estimator spreadsheet determines the junction-to-
ambient thermal resistance (θJA) based on the device, package, and airflow selected in
the main input parameters.
The PowerPlay Early Power Estimator spreadsheet calculates the total power based
on the device properties which provide θJA and the ambient and junction temperature
using the following equation:
Equation 17–1.
TJ – TA
P = ----------------
θJA
Figure 17–15 shows the Thermal Analysis section and Table 17–8 describes the
thermal analysis parameters in the PowerPlay Early Power Estimator spreadsheet.
Figure 17–15. Thermal Analysis Section
MAX II Device Handbook
© October 2008 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
