Brownout prevention circuit

[unknow005]

Dear community,

my ESP32 board reports a brownout detection ONLY while connecting and disconnection it from the power source. I belive my power source has all neccessary components but maybe I miss something?

- Power source is standard adapter with output 5V/1A
- ESP32 is powered via LD1117 LDO regulator with output 3.3V/800mA (with 100nF capacitor at its input pin)
- ESP32 power pin (2) is with 100nF and 1000uF capacitors (close as possible)
- ESP32 EN pin (3) is with 100nF capacitor (close as possible)

After power on, only Bluetooth LE is used (as server). Other peripherals (LCD, ADC ...) have each own power line directly from 5V or 3.3V supply. Of course, all periphecals power lines are with 100nF capacitors (some have 10uF tantalums too).

The circuit works 100%. Sometimes, when ESP32 reports brownout, it can take a little longer to start (from standard 1 second up to 5 seconds max). Probably due to brownout internal restarts.

Did I miss something? Maybe the brownout is caused by manual (no on/off switch installed yet) connection/disconnection of power adapter from ESP32?

Any idea how to improve the power circuit?

Thank you.
UK

[pataga]

I had restart problems when using a large capacitor e.g. 330uF on the 3V3 line. Power supply was 4.2V lipoly battery + 3V3 LDO regulator - would not reboot if I switched off and switched on again within a few seconds. Suspected the large capacitor was discharging slowly and maintaining enough residual voltage to cause problems.

I added an external voltage supervisor - this monitors the 3V3 line and keeps the ESP32 in reset if the voltage drops below a threshold - it also has hysteresis on the threshold. E.g. TPS3839K33DBZ for a nominal threshold of 2.93V. No problems after that.

https://github.com/har-in-air/ESP32_WRO ... ematic.pdf

Maybe in your case slow ramp up of the 3V3 line is causing problems as well for the ESP32. The external voltage supervisor should fix that too. If you are only seeing the internal brownout circuit reporting the issue without an actual boot / reboot issue then it is working as designed i guess.

[unknow005]

Thank you pataga.
Large capacitor and slow discharging sounds logically. I do not want to add another component to my circuit. I have added big capacitor because of wifi voltage interference but now I am using only bluetooth so I will remove it. For bluetooth it is useless.
Thanks.

[mikemoy]

FYI, a 1000uf on the output of that regulator is really over doing it. I am sure its going into current limit on startup trying to charge that cap up causing the slow ram up times.
Also the LD1117 is really the bottom of the barrel type regulator. It has very slow response times to current demands on the output.
TIP: never use a regulator that does not supply charts and curves in the data sheet.

[unknow005]

Thanks mikemoy, I did not notice that LD1117 is slow. Which cheap 3.3V regulator would you recommend?

[mikemoy]

Thanks mikemoy, I did not notice that LD1117 is slow. Which cheap 3.3V regulator would you recommend?

Need to start with what are your requirements?
Input voltage range
Current range.
Output voltage.
Cost range.
Package type.

Most of the things I build are for industrial applications, so "cheap" does not really well with these types of things.
For myself I use this in everything I build. When Input is <5.5v
https://www.digikey.com/product-detail/ ... ND/4499516

For higher input voltages typically 12v for me I use this one
https://www.digikey.com/products/en/pow ... ageSize=25

[unknow005]

Dear mikeymoy,

I preferm linear stabilizators because of minimal external components. Which parameter should I look at if I want use it for ESP32?
I need 3.3V with minimal 500mA because I use only Bluetooth LE (no Wifi).

Thank you.

[mikemoy]

I preferm linear stabilizators because of minimal external components. Which parameter should I look at if I want use it for ESP32?
I need 3.3V with minimal 500mA because I use only Bluetooth LE (no Wifi).

There is no one parameter you should look at. They all work together. You have answered 2 of the questions. You need to answer all of them to even begin to start looking for one.

[unknow005]

Hello,
almoset every regulators have multiple packages. I can customize the PCB. Components may not be available in my country other than in yours.

What about: AP2114-3.3 (SOT-223) ... looks same like LD1117 for me

Thank you.

[mikemoy]

I really cannot help much further if all of these questions are not answered.
Input voltage range
Current range.
Output voltage.
Cost range.
Package type.

IMHO, you can use the board you already have and simply try the AP2114-3.3.