Atmega sleeping: power consumption lesser with 10uF capacitor

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1

Hi to all,
background: spare Atmega328 @8MHZ, BOD disabled.

2XAA feed about 2.70 when full charge. Voltage divider to read them, power to a booster to 3.3v.
Sleeping for all time, every 10 minutes read a SI7021 and sends volt+temp+hum to a controller via NRF24L01 (time, about 5 seconds).

So, all is powered via the booster.

This is the schema, ready to print the PCB:

(link to high res: http://i.imgur.com/MTCt433.png )

If I remove the 10uF capacitor placed near the batteries, power consumption when sleep is about 1mA.

Too high for a powered battery!

WIth that cap, power consumption on sleep is 78uA (microAmpere).

Is it normal and... is it ok???

Thank you very much!

2

What you see is mostly the power consumption of your "booster". It seems to be unhappy with an unbuffered input. Maybe it is then beginning to oscillate. What, exactly, do you use as voltage converter?
The ATmega itself will have a power consumption of less than 1µA. So you should under all circumstances try to get this working without a voltage converter. Maybe use 3 instead of 2 cells, maybe smaller (AAA) if space is restricted

3

Thank you for answer.

The module is: https://it.aliexpress.com/item/DC-DC-0-8-3-3V-to-3-3V-Step-up-Boost-Power-Module-Voltage-Converter/32816387539.html?spm=2114.13010708.0.0.MihEyl

I think that I could eliminate the voltage converter.

The radio can go down to 1.9, and SI7021 as same.

Atmega has BOD disabled, so not a problem.