Replacing an unknown DC-DC converter

Hello,

i got a not working video transmitter from a friend. He used a 12V 
supply, but the part need a 5 V supply. After some measurement i found 
out that the fuse is ok, but there are three dcdc-converter which aren't 
working.
The three parts have each an inductor for filtering there outputs and 
after i desoldered it i could measure that the parts which are supplied 
ok.

Now i only need to replace the parts, but i didn't find the name of the 
IC. It is labeled with : "CB=DG", "81R".
The part has a QFN-16 case with thermal pad.

After i searched a bit and looked at some distributors i didn't find the 
part, has someone an idea what's the name of the part is ?


Regards,
Martin