How to get the best low power while in sleep mode

[Omri_Sap2020]

Hi,
My goal is as said, run my system at the lowest power I can.
I have an esp32, a dc-dc boost converter(from 3V battery to 3.3V) and some sensors.
These are 2 schematics I am considering:

1. Powering the esp32 from the 3V battery always and the sensors from the 3.3V - is it possible and correct to do so? Using an efficient dc-dc converter what magnitude of current do they take with enable off?

Screenshot 2022-01-18 223011.png (31.4 KiB) Viewed 6198 times

2. Switching between the power sources - when in active mode - esp32 is on the 3.3V, and when in sleep mode esp32 is on the 3V battery.

Screenshot 2022-01-18 223035.png (40.64 KiB) Viewed 6198 times

Which is better? Or there is a simpler alternative?
Thanks!

[ESP_Sprite]

What '3V;' battery are you thinking of using? 3.0V is very close to the minimum voltage the ESP32 module works at (it's actually right at the limit) and most battery types tend to loose a bit of voltage immediately when not entirely full. You may be better off making sure that your DC-DC is a low-quiescent one and simply running everything off of it

[moh.maya]

Are you using a standard LiPo battery? Those (the ones commonly sold for Arduino) are typically 4.2V when fully charged. I am using those for my board, and they work fine.

FWIW:
I noticed that a lot of boards use the AMS1117 LDO, but it has a fairly high drop out voltage, which could cause issues.

We're using STMicro's LD39100PU33R, and that is working well for us. https://www.digikey.com/en/products/det ... 3R/6579072

[Omri_Sap2020]

Thanks for the replies!
According to what I saw, ESP32 still works with 2.5V. I am using a non-rechagable lithium battery due to size and price(in compare with 4.2 lithium). I might change that in the future, but for now I see no reason.
The problem with putting the converter at the beginning is that a good quiescent current reaches ~20uA and ESP32 in sleep mode can go down to ~10uA or even less and that is a big gap for me(aspiring to survive for years).
LD39100PU33R also has "high" quiescent current that I would like to avoid consuming.

[ESP_Sprite]

According to what I saw, ESP32 still works with 2.5V.

It depends. The chip itself can go quite low, but it's usually limited by the flash chip that comes along with it. If you are building your own PCB with a separate ESP32 and flash chip that can work at a low voltage, then you can likely make it work at 2.5V. If you use a devboard or module; these are generally rated at 3.0V minimum. If those happen to work at 2.5V, good for you, but know that we at Espresif don't guarantee anything there.

[Omri_Sap2020]

It depends. The chip itself can go quite low, but it's usually limited by the flash chip that comes along with it. If you are building your own PCB with a separate ESP32 and flash chip that can work at a low voltage, then you can likely make it work at 2.5V. If you use a devboard or module; these are generally rated at 3.0V minimum. If those happen to work at 2.5V, good for you, but know that we at Espresif don't guarantee anything there.

Ok, I use my own PCB with seperate ESP32 and a flash chip.