Question on TVP54310 thermal pad

Tat is requiring a minimum of 3.3 square inches of copper area connected to the exposed powerpad under the device.  For pest results, that copper should be on teh back side and conneted to the powerpad area on the top side with thermal vias.  BTW, you keep referencing EVM6437.  What is that design? Where did you get it?

That is according to that reference design, I suppose it was tested and checked, but I have no firsthand knowledge of it.  When I design using these parts, I tie the power pad to the internal ground plane if one exists.  I tie the AGND pin to the thermal pad area as well with a single trace directly under the IC.  I tie the sensitive analog returns (v feedback, RT, SS/ENA, etc to the AGND pin with a dedicated trace on teh top side.  For 3 amp designs that is probably sufficient, but our EVMs almost always have some copper on teh back side directly under the device connected to the exposed pad area by thermal vias.  Copper on teh outer (front and vack side) are more efficient at transferring heat to the ambient air.

If you want to follow that reference design, you should contact the designer directly.

You definitely get better heat transfer with a solid connection.  Thermal releif connections are just that, to inhibit heat transer, not to facilitate it.  That reference design may still have sufficient thermal path, I did not work on or do any testing with that design.  For your purposes, I highly recommend that you use the solid connection.