Supply voltage for C4

I'm trying to use a battery pack that i bought to make a beagleboard
C4 portable.
The battery pack that I've bought ha a solar panel for the recharge,
or could be recharged by pluggin in a USB port.
The main problem is that the possible output are 3.3V 4.2V 5.5V.
My question is: is 4.2V enough to supply the board?
Second question: is 5.5V safety?
PS: I was also thinking about buy a MX, can I use the same battery
pack with it (see questions above).

The internal supplies run from and LDO that drops the voltage to 4.2 for the on board power management device. You need at elast 4.8 volts for it to work properly, but it could work at 4.2V. However, if you want to use the USB port, then you must have 5V coming in. USB requires 5V. Using 5.5V is risky not so much from a Beagle standpoint but from a USB standpoint. It could potentially damage USB devices. You could add a series resistor to drop the 5.5V down to closer to 5V, but then you are wasting some of your battery life through the resistor.

The -xM has an integrated over voltage alert and shutdown system that triggers when the 5V is too high. 5.5V, depending on exactly how much it really is, could trip that circuit. In addition the -xM has 4 USB ports and an on board HUB which takes more current. But, overall it should work but it may not last as long.


Thanks for the fast reply. I've already thought about a method to drop
the voltage, adn I think that a diode should do the trick (0.5-0.7V)
of voltage drop coul de good.
Just to see if I understood right, If I supply 5.5V the risk if low
for the beagleboard since the regulator provide the omap the correct
voltage, but could be dangerouse for the usb peripherals connected to
the usb ports.
And if I use an external Hub? that should correct the VUSB values...

Using a powered hub is OK, but that hub would still be subjected to the higher voltage level, but I would expect it to be a little more robust in handling the higher voltage. If the battery pack has a voltage booster that would also keep thee voltage at a constant value, but if it is a straight battery configuration, the 5V could drop to the point where it wouldn’t work even though the board could keep working.