Leakage power increases exponentially with respect to junction temperature. Thus, it is very important to accurately specify the environment conditions in PDM. The environment settings allow the following flows:
- User Specified Junction Temperature
- Enter the targeted junction temperature or the maximum junction temperature of
the device and ambient temperature.
- PDM calculates maximum Effective ΘJA to meet requirements (the Effective ΘJA field is read-only).
- PDM Estimated Junction Temperature
- Enter ambient temperature and Effective
ΘJA, from which PDM calculates the junction
temperature.
- Derive Effective ΘJA from thermal simulation.
Note: PDM uses the thermal settings only to
calculate the junction temperature based on the following formula:
Junction Temperature =
Ambient Temperature + (Effective ΘJA * Total On-chip
Power)
Important: PDM does not perform thermal analysis
to calculate the effective ΘJA. It reports the requirements based on given junction
temperature and ambient temperature values. Xilinx suggests that you
replace the PDM populated maximum Effective ΘJA with the determined Effective ΘJA from
thermal analysis of the system, preferably from thermal simulation or actual system
measurement.
PDM alerts you if the specified or calculated junction temperature exceeds the device temperature grade margin.
Figure 1. Thermal Settings in PDM

Note:
Xilinx
provides thermal models for both Siemens Flotherm and Ansys IcePak. Xilinx recommends you to perform a system-level thermal simulation. This
allows you to effectively assess the conditions and use the effective ΘJA parameter from
simulation to estimate accurate device junction temperature in PDM.