Hi all,
after I stumbled upon a few rather short comments about running the Olimex SAM7-256 at 5V whereas the data sheet clearly states 6V to 9V, I’m wondering if anybody here has any real-life experiences with running the devboard at 5V.
I’d really like to use SFE’s [USB to 5.5mm Barrel Jack Adapter to power my board…
Regards,
Alexander](http://www.sparkfun.com/commerce/product_info.php?products_id=8639)
Uses LM1117 regulator.
In my NXP LPC2106 boards, that regulator will not work at anything less than 6V because of the diode drops in the bridge that protects from reverse polarity.
If you bypass the bridge and if you NEVER reverse the polarity by mistake, it’ll probably work on 5V, as the LM1117 is an LDO. It’s spec’d at 1.2Volts of headroom, so that would be 3.3 + 1.2 = 4.5V min.
The bridge diodes add about 1.4V to that min.
HOWEVER, doesn’t that schematic show a 5V feed from the USB port via a shottky, so that’d be 5.0 less 0.3 = 4.7 into the LM1117 with USB as the DC source.
Like mentioned, it can be powered directly from its on board USB connector. Not certain why you would want to use another USB connector. I have one of those header boards I can try it on 5V on VIN. When I used it, I just supplied 3.3V from an external regulator to the 3.3V in lines.
I’ll have to give it a try this weekend some time.
Thanks for your answers!
Instead of bypassing I’ll just use either the on-board USB connector or 2 LiPo cells which should give me between 6.0V and 8.4V.
However, I just noticed that using the boards power connector, only 3.3V are available whereas when using the USB connector, also the on-board 5V connector (located in the upper right) is powered. Is that right or did I miss something?