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### Topic: Power Arduino Nano from 3 or 4 rechargeable AA NiMH batteries? (Read 298 times)previous topic - next topic

#### Wookbert

#15
##### Aug 21, 2019, 06:42 pm
According to how I read that datasheet, there's really a 3.3 to 6V range on Vcc, so not involving a voltage regulator. It says Raw (so with voltage regulator) is 4-16V.

#### septillion

#16
##### Aug 21, 2019, 07:04 pm
First note you are NOT looking at a datasheet Merely a spec sheet.

And yes, the 6V is indeed the absolute maximum (aka, no margin at all) voltage for the ATmega directly (aka, no voltage regulator), safer to stay under 5,5V. But you are mixing some things. Nowhere does it mention 3,3V as a minimum Also, because you can't speak of a fixed current for a micro and 500mA is wayyyyyyyy more then the ATmega will ever draw we will have to assume they do talk about the voltage regulator there. Same for the 3,3V to be the normal Vcc (aka, from the voltage regulator).

And digging deeper, that does indeed match with the schematic and the datasheet of the voltage regulator. So my instinct as an electrical engineer is correct

Having said that, 500mA is the max current for the regulator but if you apply a high Vin, the thermal limits of the voltage regulator will be met waayyyyyyy before that!
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#### Wookbert

#17
##### Aug 21, 2019, 07:23 pm
I stated 3.3V to be the minimum, simply because I couldn't find a minimum specification. What's the minimum Vcc at which the Pro Micro still works in your opinion?

But I do understand those figures (3.3-6V) correctly in that both

• 3 pcs. AA rechargeables (3x 1.2-1.4V = 3.6-4.2V)  or
• 3 pcs. AA alkalines (3x 1.5-1.65V = 4.5-4.95V)

would actually work?

#### septillion

#18
##### Aug 21, 2019, 07:26 pmLast Edit: Aug 21, 2019, 07:27 pm by septillion
What's the minimum Vcc at which the Pro Micro still works in your opinion understanding?
That will be in the Datasheet of the ATmega32U4 Probably under electrical.

Yep, chapter 29.6. 8MHz down to 2,7V
would actually work?
For the ATmega, yep. Sensors, no idea.
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#### Wookbert

#19
##### Aug 21, 2019, 07:51 pmLast Edit: Aug 22, 2019, 09:21 am by Wookbert
That will be in the Datasheet of the ATmega32U4 Probably under electrical.

Yep, chapter 29.6. 8MHz down to 2,7V
Sorry, didn't actually notice that post.

Another question: Do I understand this thread on methods for reducing power consumption on the Mini correctly in that the voltage regulator draws power, even if power supplied via the board's Vcc pin (e.g. to provide the power for the LED?) In post #11 they are cutting pin 5 (which if it's an MIC5219-3.3BM5, should be Vout).

#### septillion

#20
##### Aug 22, 2019, 09:30 am
Yeah, it's pretty common for a regulator to have a leakage current when powered from "the wrong end". So removing it is indeed beneficial.
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