More on the U7 voltage regulator
The XL_STAR schematic dated Monday 21st February 2011 does not contain any details of U7 (the IC that can get really hot).
From the picture in the XL_STAR Users Manual on page 9, U7 and C28 have replaced U2 and L4.
The left is the photo in the manual, on the right is a photo of my XL_STAR with the U7 alternative.
U7 is marked with L048B but the closest device I've found is a National DP8345 but according to its data sheet it does not come in a SOT23-5 package. It'll be interesting to see what it is. (It's obvious that it is a 3.3 voltage regulator to replace the MC34727CFC!)
The MC34727CFC looked the perfect part with 3.3V 600mA power output with an input voltage range of 3.6-5.5V ensuring operation with a LIR/PD2450 battery. The battery wouldn't last too long pumping out the power for 600mA.