Deep Sleep / Low Power mode question

[d00m178]

If you want to minimize power, you need to remove the LDO and feed clean power into the Vin pin.

sorry, but - if I remove LDO from PCB how can I power Moteino via Vin? Vin pin will be completely disconnected after removing LDO module.
or it is just typo and you have meant 3.3v pin?

as for my power source - I need more that 2000 mAh for my project.. in Active mode my device consumes about 150mAh (RX/TX LoRa, 10 termosensors d18b20, photoresistor, laser module, mosfet..  ) and I need my device work for 4-5 month.. So I use LiPo pack with at least 6000mAh..

[ChemE]

http://ww1.microchip.com/downloads/en/DeviceDoc/22049e.pdf

You would also need to jumper the pads for pin 2 and pin 3 on the MCP1703 footprint to get power from Vin to the rest of the PCB.

[WhiteHare]

An advantage to jumpering it like ChemE says is that you can then use a 3.3v FTDI connector, as per normal.  However, if d00m178 doesn't care about that, then I'm not aware of any problems arising from simply removing the LDO and then powering it through the 3.3v connector if that's how d00m178 prefers to do it.  Just be sure you don't exceed 3.6v.  If you run with BOD disabled, then it's all on you to guarantee the voltage never drops below 1.8v, including under load.

[d00m178]

http://ww1.microchip.com/downloads/en/DeviceDoc/22049e.pdf

You would also need to jumper the pads for pin 2 and pin 3 on the MCP1703 footprint to get power from Vin to the rest of the PCB.

If I remove LDO and put jumper wire from pin 2 to pin 3 does not this mean the same thing as power Moteino from 3.3v pin?
Please check attached image - seems it is the same contacts - 3.3v and LDO pin 3.

Also please check this link:
http://www.home-automation-community.com/arduino-low-power-how-to-run-atmega328p-for-a-year-on-coin-cell-battery/

There stated:

The ATmega328P running at 8 MHz can actually support voltage levels between 2.7 V and 5.5 V

So I supposed that it means that I can power Moteino via 3.3v pin from LiPo battery fully charged to 4.25v
Am I right or it is definitely mistake?

An advantage to jumpering it like ChemE says is that you can then use a 3.3v FTDI connector, as per normal.

I can use FTDI adapted without its power line connected - I just poweri Moteino from battery during re-programming. Is it Ok?


So it is still open question about powering MCU via 3.3v from LiPo 4.25v..
Is it ok or not.

[WhiteHare]

So it is still open question about powering MCU via 3.3v from LiPo 4.25v..
Is it ok or not.

No!  You'll fry the radio.

[WhiteHare]

Just be sure you don't exceed 3.6v.

[d00m178]

well, thank you for your answer.

Actually it already works as I described - via 3.3v pin from LiPo - send/receive OK.
But I will change it back - will use LiPo with LDO..

[ChemE]

From what I've gathered on the forums (and others might need to correct me) feeding 4.25V into the 3v3 pin is back driving your LDO.  This causes it to use vastly more current than if your were feeding that same 4.25V into the Vin.  It would seem that back driven, it still brings the voltage down to <3.6V and prevents you from frying your radio which itself is not rated to 4.5V even though the 328p is.  If you remove your LDO and feed 4.25V in, you will nuke your radio.

[d00m178]

If you remove your LDO and feed 4.25V in, you will nuke your radio.

No, I removed LDO and my device works at least couple hours with LiPo on 3.3v pin.
But I noticed strange behavior - in sleep mode device consumes more current (~1,8  mAh) than with LDO and LiPo on Vin (50 uA)..

[WhiteHare]

But I noticed strange behavior - in sleep mode device consumes more current (~1,8  mAh) than with LDO and LiPo on Vin (50 uA)..

Moot.