I am planning to power Arduino using a solar panel but under low solar intensity to power it through a lipo battery 3.7V. I am thinking to use a step-up converter connected to the lipo. Could you please advise what is the lowest step-up converter that I could properly power Due? 5V, 6V or higher?
If you don't want to use any of the 5v peripherals on the board, you could feasibly power it from 3.3v. The 3.3v regulator takes its power from the 5v rail so it would initially make sense to feed 3.7v in there, but then it would be running the 5v components at that reduced voltage and you presumably want to minimise that power consumption.
I would expect that you could put your own 3.3v regulator on the 3.7v supply and feed the 3.3v pin on the Due.
Thanks for your advice!