Re: ESP32-S2: need to adjust Brown Out Level at runtime
Posted: Sat Feb 10, 2024 10:49 am
I can't find data on any hysteresis of the BOD either. You may look into implementing it it software: Start up and set the BOD to, say, 3.0V; when the BOD triggers (interrupt), do your shutdown/cleanup routine, then set BOD to 3.3V to reset the chip and hold it there until power comes back.FiwiDev wrote: ↑Fri Feb 09, 2024 11:52 pmThat doesn't solve the problem of the ESP32 brown-out module being effectively useless.MicroController wrote: ↑Fri Feb 09, 2024 9:05 pmAnother potential option: "5V" ultracap (2x 2.5V in series) hooked up directly to 3V3
20F?! What are you trying to do? Aren't we talking about buying a few tens/hundred ms to cleanly shut down?(Also worth noting that boost converter ICs are significantly cheaper than ultracaps: TPS61023 with true disconnect functionality is ~$0.23 + associated parts, and the 3.0v 20F ELDC low-ESR ultracap I am utilizing comes in at ~$1/ea.)
Edit: "after running shutdown tasks comprising several seconds.." - Nope, we're not
Inrush current - nothing that can't be fixed with a diode/FET and a single resistorAnother thing to keep in mind is that "directly to 3V3" will put a considerable load on the 3.3v rail when the capacitors are completely empty. (That of course is assuming that the ultracaps have a low ESR--which they have to be in order to be able to power the ESP32 without causing random crashing due to chip brownout. The EDLC ultracap I have is rated 50mOhm [0.05 ohms], and Ohm's Law states 3.3v across 50mOhm will pull a cool 66 amps!)
Also, the ESPs tend to draw maximum power (500mA or so) only in short spikes during RF activity, so you may not actually need 20F of low ESR to get down to the impedance required.