Thanks both. Very helpful information.
Simon, question about a part in your tutorial. When the MOSFET turns off, "the right hand side of the inductor has to increase in voltage with respect to the left hand side. The left hand side is connected to the input voltage (so cannot change), thus the right hand side voltage increases above the input voltage and continues to do so until something conducts."
From the circuit on your webpage, why doesn't current back flow into the input source as soon as any part of the inductor exceeds 3.3V? Obviously, it doesn't (or boosters wouldn't work), but I don't see why it doesn't.