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Topic: Will Atmega328 (with 8mhz int osc) start with lowest charge of 2AA Duracell (Read 726 times) previous topic - next topic

wonderfuliot

Hi,

I want to use 2AA Duracells to power Atmega328 that will run with 8Mhz internal oscillator.
Will the chip run at the lower voltages of the cells?

Thanks and Regards,
WonderfulIOT


CrossRoads

Yes it can, see the speed grade chart in the datasheet.

You may need to set the Extended Fuse Byte for a lower Brown Out Detection level.

These are for a '2560, '328 has similar chart.


Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Jiggy-Ninja

According to the datasheet, 8 MHz requires 2.4V to be guaranteed to work. Due to tolerance variations you could probably get away with some degree of undervolting, but you're operating outside of spec when you do that. If you want to run down all the way to the minimum 1.8V supply, you need to operate at 4 MHz or less.

If you're changing fuses to run with the internal oscillator, you can also turn on the CLKDIV8 fuse. This will cause the clock to run 8x slower at start up, so the 8 MHz internal oscillator becomes 1 MHz. The clock prescaler can be changed in code so you can bump it up to 4 Mhz if you want.

wonderfuliot

If you're changing fuses to run with the internal oscillator, you can also turn on the CLKDIV8 fuse. This will cause the clock to run 8x slower at start up, so the 8 MHz internal oscillator becomes 1 MHz. The clock prescaler can be changed in code so you can bump it up to 4 Mhz if you want.
But even though the oscillator is producing 1 MHz, yet, it is still running off an 8MHz RC oscillator and thus out of voltage range?

Linking a similar thread.

http://forum.arduino.cc/index.php?topic=586725.0


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