Looking to use something like a LT3988 switching regulator or a LT3990 to get generate a 12V supply (50mA max load) for a project I'm working on.
Input voltage would be +24 to +48VDC
But my question is that I would also like it to also accept -48VDC as the input voltage.
Would just a diode bridge before the input to the LT part work? Or what are the better/recommended ways to accomplish this..

and in no way am I tied to those LT parts just the first few I came across..

 

Sure a diode bridge is a good way to steer the right polarity of the input to + and - of regulator.

 

The bridge will work only if the input voltages are floating with respect to the regulator's ground.

 

It seems to me that the only purpose of using a bridge would be if the input polarity is unknown.