I would like to be able to run an AVR at either 3v3 or 5v (don't mind either way but it probably makes no difference to the problem) with an input range to a regulator of 1v5 to 15v.
There are buck/boost regs but AFAIK they all have a max of 5v.
The best idea I can come up with so far is a linear or buck reg AND a boost reg, parallel them and diode OR the outputs. Another way is to buck down to ~2v and internally connect that to a separate ~2v input and boost back up to 3v3 or 5v.
I don't mind having two separate physical inputs, but one would be better.
Of course I want it to be free and use no components :)
Why? I'm designing a dongle that can connect to batteries in a battery bank (as in large solar power banks) and the three common battery sizes are 2, 6 and 12 volts.
6 and 12 are no problem, but 2 is a PITA and I don't want to have two versions of this gadget.