LT3750

Hello, I am working on a cap charger for an avoinics power supply design.  We need to run from a 280VDC bus to charge 20,000uF of cap from 0-280V with a max current of 30A (time is less of an issue).  I am looking at the LT3750 or LT3751 but have several questions.  Has anyone implemented this IC in a similar application?  After scrubbing through the TDS, it is unclear how the bus would attach (would this be switched onto the secondary cathode?).  Is the Vtrans driven from an external regulator or a buck off the bus? Also, what transformer would be recommended for this application?  I appologize in advance for the elementary quesitons, however have never used an active charger before.  I calculated 729J which is not reasonable for a passive solution and this part looks promising.Thanks!