I'm currently designing a battery powered, 2xAA in this case, project. The problem that I have is very simple, I want to power a DS1307 (the only part in my circuit which requires 5V). I've looked into similar parts like the DS1337 and the MCP7940, which operate under 3V, but they don't have a battery backup pin like the DS1307, which is something I want.
So, the first thing that I thought was to build a step-up DC/DC converter circuit to power the RTC (that's the first thing I thought, so I'm open for suggestions). Since I never used a switchmode converter before I decided to watch Dave's video about the MC34063, but the problem with it is that its minimum input voltage is 3V. So I would like to know some tips on how to choose a suitable switchmode converter for this kind of project.