deep sleep current below 500 uA? T-Call SIM800C AXP

[ClemensGruber]

There is a nice documentation of the 500 uA deep sleep current for the (new) T-Call with SIM800C with AXP192.

I wonder is this the lowest limit, or can we go below? The T-Call is a ESP32 with AXP192 power management chip from LilyGo, the reason for my hope is the T-Beam, also a ESP32 wie AXP192, also from LilyGo aaaaand with this numbers:

Sleep current: 0.2uA@SLEEP 1.5uA@IDLE

I had a look at the T-Call schematic but I'm not quite sure if the AXP192 can disable the power line for the SIM800 completely. I assume that this would be the requirement for a really low deep sleep current. Any knowledge about that?

I found this code snippets to have a deeper look for power saving:

• Paxcounter https://github.com/cyberman54/ESP32-Paxcounter/blob/master/src/power.cpp

• AXP-Bibliothek, sleep example https://github.com/lewisxhe/AXP202X_Library/tree/master/examples/axp_sleep_mode

Is it worth to go this path -- and the code above the right place -- or is the 500 uA the last word (by hardware design) we have to accept? Or any other advice where to start for this question?

[ClemensGruber]

I did some investigation about the deep sleep current of the T-Call with AXP and found the already reported average deep sleep current of ~500 uA. With a more elaborated setup you can see 4.3 mA peaks every 3.5 ms. Has anyone an idea what this could be and how to stopp the AXP -- I think it is the AXP and not the ESP -- "wasting" energy?