Leakage power increases exponentially with respect to junction temperature. Thus, it is very important to accurately specify the environment conditions in XPE. 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.
- XPE calculates maximum Effective ΘJA to meet requirements (the Effective ΘJA field is read-only).
- XPE estimated junction temperature
- Enter ambient temperature and effective ΘJA, from which XPE
calculates the junction temperature.
- Derive Effective ΘJA from thermal simulation
Note: XPE 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: XPE 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 XPE populated maximum Effective ΘJA with the determined Effective ΘJA from thermal analysis of the system, preferably from thermal simulation or actual system measurement.
XPE alerts you if the specified or calculated junction temperature exceeds the device temperature grade margin.
Figure 1. Thermal Settings in XPE
Note: Xilinx provides thermal models for both Siemens Flotherm and Ansys IcePak, accessed via the power design sheet or at Versal Thermal Models. See Power Supply Design to enable accurate thermal simulation. It is recommended that you perform a 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 XPE.