Thermal Design User Guide: Agilex™ 3 FPGAs and SoCs

ID 851249
Date 5/12/2025
Public
Document Table of Contents

7.3. Example 3: Find the Ambient Temperature for a Specified Cooling Solution

In this example you have a thermal solution already assigned or available, and the TJ-MAX of the device is set. You must determine the maximum ambient temperature under which this thermal solution works. The example assumes the heat sink has an effective ΨCA of 20°C/W.

The module’s thermal solution includes a 50mm x 50mm x 25mm heat sink, no air flow, and the device is on a 10-layer board.

From the table in the Variables Affecting the Heat Flow Path topic, we know that the percentage heat transfer to the heat sink is 55%.

To input the cooling solution ΨCA value into the PTC Thermal tab, you perform the following calculation:

In the PTC Thermal tab, choose the calculation mode as Find ambient temperature for specified cooling solution.

Input the ΨCA of 11°C/W and the TJ-MAX of 100°C.

Figure 14. Example 3, PTC Main tab

The PTC Thermal tab indicates that the cooling solution is adequate for an ambient temperature of up to 56°C.