TPS65265: Operation at VIN=4.5 and switching frequency

Part Number:TPS65265

Hi,

I am planning to use TPS65265 as a secondary regulator to generate the following rails:

0.85V @ 5A

1.2V @ 2A

1.8V @ 1A

From reading the datasheet it says that V7V is generated as 6.1V typical, using an LDO from PVIN1=12V. Since an LDO is used clearly V7V must be <4.5V when a 4.5V input voltage is used. Therefore I wanted to confirm that operation from this input voltage will be OK?  

In addition it is not explained how the selection of switching frequency should be made. There is a wide range of possible frequencies that could be used. Can a methodology for selection be proposed?

Thanks,

Tom