ESP Boot fail after restoring power from lack of power source.

wnoliveira
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Joined: Wed Feb 06, 2019 6:45 pm

ESP Boot fail after restoring power from lack of power source.

Postby wnoliveira » Wed Mar 25, 2020 6:55 pm

Hi all.

I am facing a problem with ESP32-WROOM (chip revision 1).
I have two boards with this same chip:
-> Board "A" has an old power supply with a rise time (from Vcc = 0V to Vcc = 3.3V) around 50ms.
-> Board "B" is a new board, with a newer power supply. This rise time is around 0.7 ms.

Both boards successfuly boot at the first time. But, when the main power supply goes down for a few ms (sufficient to down the voltage of ESP32 Vcc to 1V) and goes up again, until 3v3, only the "B" board can boot again properly. Board "A" just boot if this "lack of voltage" goes under 1V; if not, it does not boot.

Below I've attached the ESP32 VCC waveform of both boards. The upper dashed line represents 1V.

Board A
Image

Board B
Image

I don't know if it is a problem of Brownout circuit or something like that. If someone has any idea, please answer that.

Thank you a lot!


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