Deep sleep Power consumption Problem.

[ManuelV]

We have a custom ESP32 Module and we use it mainly in deep sleep mode.

I was able to get the power consumption down to 4uA ( on my 7.2V input). But now i'm having a very strange problem and i'm not able to find it:

When I start my device, the power consumption is 40uA ( 7.2V ). It stays like that until the ULP wakes up the ESP, executes the code and then it goes back to consume 40uA.

Now when i just touch the ESP_ENABLE pin. ( I have a 100kPullup there) then the power consumption instantly goes down to 4uA, and stays like that even after the ESP wakes up, executes the code and goes back to ULP-Sleep.


Any Idea?

[pratik2440]

What do you mean tuoch the EN pin? You mean ground it or just touch by hand?
The EN pin has some timing requirements after power-up (check the ESP32 datasheet). So if you have a 100K pullup, you should have a "pull-down" capacitor of 10nF or something like that to meet timing requirements. Otherwise the chip does not boot up normally and behaves weird.

[ManuelV]

Touch it with some metal.. seems a capitative thing .. it really sounds strange.

I also tried to change the Pullup to a 10k and add a 100n Capacitor to ground. The power consumption stays the same, but the trick with touching the EN pin does not work anymore.

I also noticed some other strange behavior while touching..

Some pins have Software Pullups set. When I touch the EN pin, those GPIO"s go to low instantly, and the power consumption drops to 4uA. After the wakup-cylce the pins are high again. ( Power consumption stays at 4uA so those pins are not the problem)

[pratik2440]

It could be a grounding problem of some sort. Make sure your ground connections are good and do not form a ground loop. That tends to make the EN and interrupt pins extremely sensitive on the ESP32.
10K and 100nF is the recommended value. If you skip that cap, the EN pin can malfunction.

Also, have you checked the power supply voltage and noise level at 4uA? It could be that the power regulator is somehow not handling low current output properly.
Many linear regulator ICs have a "minimum load" requirement. If you draw less, they go out of regulation.