TPS548A29: IC heat issue

Hi Chunming, 

First, I would say that AGND and PGND should be separate grounds and it should be connected at a single point on an inner layer. 

Mode, Trip, and EN should be connected to AGND. With an output current of 7.2 A, recommend using an Rtrip of 6.65 k to have a higher over current limit at around 9.5 A. A Cff of 100 pF is required for this design. 

Regarding temperature, how hot is very high? Based on the datasheet the thermal image shows the IC reaching 68 deg C. 

Layout is an important factor to improving thermals, here is an app note on how layout can improve thermals. Having more layers, larger planes, more vias can improve thermals. 

Thermal Performance Optimization of High Power Density Buck Converters

Best,

Ryan

Hi Ryan

The temperature of ic is above 80℃, as shown in the figure below.

Should AGND and PGND  be connected with a bead? And the layout is shown in the figure below. Do you have any suggestion?

Thank you~

Hi Chunming, 

AGND and PGND can be connected using a net tie at a single point on an inner layer with a large PGND and AGND pour. I would recommend following the datasheet layout recommendations and guidelines. One thing I see, if you are not constrained in size, is to have more spacing in between components, one example is that your output caps are almost touching your input capacitors. 

Best,

Ryan