Power for AVR-CAN Board:
1. When powered by OBD (12v nominal but might be 14v), I generally go through a 5v (1 watt) zener diode. That external "power-in" feeds an on-board regulator to produce the well-regulated 5v that the board actually uses.
2. Sometimes a board can be powered by a USB-powered JTAG programmer, where the 5v goes directly to the board's 5v buss. However the AVR-CAN's 5v buss is powered by an on-board regulator, so this method shoud NOT be used to powet the AVR-CAN board.
3. The AVR-CAN could be powered by a 9v battery, but one must be careful to NOT lose power in the middle of flashing, or the micro-processor could become un-responsive (effectively dead). I do not have enough experience with the Atmel AT90CAN123 uP to evaluate the risk, but it usually exists.
4. Finally: I use an inexpensive ($4), all-voltage, AC-to-DC power supply (CA-590) that produces well-regulated 8.4v (600 ma) DC ... that was originally made to power a Canon camera, as I recall. I just found it for this project, and bought a couple. It seems to work well.
NOTE: The "well-regulated" symbol/icon/mark is (I THINK) a small square outline with another small square outline within the first. OR, this icon might just mean double-insulated, I an not sure.
Non-regulated (or poorly-regulated) power supplies generally produce something near the rated output voltage ONLY when loaded down enough to supply approximately the rated current. When lightly loaded (or un-loaded) they can produce a WAY higher voltage, and should generally NOT be used with computer type circuitry.
This Canon switching Power Supply is catalog part number PS-846 at