This app note has some additional details about the subject.
Powering the AD9268 Dual Channel, 16-bit, 125 MSPS Analog-to-Digital Converter with the ADP2114 Synchronous Step-Down DC-to-DC Regulator for Increased Efficiency
http://www.analog.com/static/imported-files/circuit_notes/cn0137.pdf
ADI also publishes proven solutiuon on the EVAL board documentations and Wiki pages.
This is an example of the AD9250 board showing another implementation of a low noise supply
http://wiki.analog.com/resources/eval/ad9250-ad6673ebz
http://wiki.analog.com/_media/resources/eval/user-guides/ad9250_schematic_02_12008.pdf
Look for additional Wiki, app notes and CN to be published on the subject in the coming months.
LucaV
