Question
I want to make a programmable LDO. What devices could I use?
Answer
For this application, I'd recommend a digital potentiometer such as the AD5141
plus one of our LDOs, in linear gain setting mode.
You can select any of our LDOs, ie. ADP1708, and place the AD5141 in the
feedback loop.
In this case, configuring the digipot in linear gain setting mode, the error
will be ratiometric, so you should expect voltage error due to resistor
mismatch below 1%.
http://www.analog.com/static/imported-files/application_notes/AN-1169.pdf