THS4061: THS4061DGN Thermal Pad Potential

Part Number: THS4061

Tool/software:

I'm looking to be able to alternately populate a THS4631DGN with a THS4061DGN.  The powerpad pad for the THS4631DGN is specified to be internally connected to the negative rail (V-) while the THS4061DGN does not specify any internal connection to the powerpad.  Is it truely floating and can it be tied to the negative rail as well?  I don't want to assume anything and my experience has been that those pads are typically tied to some potential internally.