Hi all
I'm just received the Arduino board and found a strange 3-legs-chip (named 269-5G RA823) near the power connector, whose central leg is cut and not connected to the pad.
Is it OK?
Yes it's normal.
You can sort of see it here
And a bit clearer here
http://www.flickr.com/photos/stevencogswell/3327157128/sizes/o/
Top-down isn't best for this, but you can see the white silkscreen stripe passing under the silver cut pin in this view:
http://halley.cc/arduino/arduino-duemilanove-9v.jpg [[large]]
Oh, thanks - I'm not worried anymore 
But what is this chip for? I didn't find it in the schematics and also google "269-5G RA823" gave no results...
Is it some kind of DC-DC converter or somtheing else?
But what is this chip for?
Is it some kind of DC-DC converter or somtheing else
It's a plain ol' 5v linear regulator.
I didn't find it in the schematics and also google "269-5G RA823" gave no results...
The schematic shows the part number as "mc33269d-5.0". A datasheet is here
whose central leg is cut and not connected to the pad
This is typical of 3 pin DPAK regulators. The heatsink tab is actually used as the ground pad.
The heatsink tab is actually used as the ground pad.
Note that while the heatsink is the third regulator lead, it is NOT always ground. It is typically connected to the output voltage for "low drop out" (LDO) regulators, like the one used on Diecimila (and later.)
WestFw is completely correct, it's Vout on this chip too. I really need to proof read posts better.
Oh... spiffed, westfw, thank you for such detailed expanation!