Correlate to Simulation and Update Thermal Power Estimation Data

Designing Heatsinks and Thermal Solutions for Xilinx Devices (XAPP1377)

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An important but often overlooked step for the debug and finalization stages of the design is to relate any measurement data to the simulation and thermal power estimation constraints. Often towards the end of the design, proper time is not allocated to take the measurement data and compare with the initial assumptions and constraints as a means to both refine them for the current project as well as improve the initial assumptions for the next project. This allows for more confident updates and debug for the project if the need arises. Also, for future designs, it allows for a tightening of assumptions to allow for greater optimization and accuracy during the iteration.

The first step to this is to compare the measurements, particularly the junction temperature, with those seen during the simulation. If there are any noticeable deviations, explore how the thermal modeling can be improved to get a more accurate result. As for the power estimations, the design continues to develop and evolve after this thermal characterization takes place, and many times future updates can be applied. By reassessing and updating the thermal parameters to the XPE and Vivado power estimations, any subsequent updates can more accurately assess the impact against the fixed thermal solution. To do so, simply update the prior Effective θJA to the measured data.

Figure 1. Effective θJA Calculation for Power Estimation Based on Measurement Results

This new data should be applied to XPE and Vivado similarly to what was referenced in the Evaluating Simulation Results section.