Running atmega168 and 328 at lower voltages

Forum 2005-2010 (read only) Hardware Interfacing
1

I always thought that the atmega chip required 5v to run. I noticed on sparkfun site that they can actually run lower but then I have to use a slower oscillator.

I assume that if I run it at 3.3v then I can hook it directly to my other 3.3 boards (sd card reader and mini-mp3 board) with logic HIGH now being 3.3v instead of 5v. Is this correct?

If so, does anyone know what speed oscillator I could use?

Final question. Other than changing the 7805 to a 3.3v regulator, and changing the oscillator, is there anything else I need to do?

Thanks,
Ben

2

If it's a USB device, it will get 5V from USB. An older arduino (e.g. the NG) has a jumper to change power from USB to external. You can change the 7805 for a 7833, switch the jumper to EXT, and power it from the coax power jack or the 9v pin.

If it's a newer model that automatically switches power, I'm not sure how (or if) that wold work out.

-j

3

I've been running over a dozen 168/328's (mostly 168) at 3.3V and 16 MHz, no problems so far. Not. One.

I've blogged about this at:

http://jeelab.equi4.com/2009/02/27/out-of-spec/

Would love to hear about other experiences with running AVR's at 3.3V.