SLYA094 August 2025 LM5137F-Q1
3.2 Thermal Performance
Both Figure 3-2 and Figure 3-3 show thermal performance of reference designs taken at a room temp of 25℃, open frame, no air flow. As you can see, when Iout is 21A, the max rising temperature is only about 25.5℃, while if Iout is 42A, the max rising temperature is about 73.4℃. So better to add a heatsink at the bottom side of conveter.
Figure 3-2 13.5V in, 4.5V out at 21A Thermal Image
Figure 3-3 13.5V in, 4.5V out at 42A Thermal Image