Very slow start on switching regulator

Other Hardware General Electronics
1

Hi. I made a design for a circuit, a buck regulator based on this one.

I don't know what I did wrong (I used the same values as the schematic for the components), but in my version the output voltage raises very slowly to its final value (it takes 3 seconds to reach 5v).

For my application this doesn't work: I have it attached to an ESP-01, through some diodes to reduce the voltage even further, but the ESP almost never turns on. I tried with a physical switch at the output of the regulator and it works when switched on after reaching 5v. That's why I know that the problem is related to the slow raise.

So, why does my regulator do this? And which component can I add to turn the circuit on once reached the desired voltage?

Thank you.

2

First, all voltage regulators are amplifiers with feedback. Follow your feedback path for an error. How do you know the schematic matches the linked regulator? Does the schematic have revision dates and do you have the latest?

3

Sorry, I found a pivotal difference between my version and the one from the datasheet (and Sparkfun's one). I placed a wrong value capacitor on the feedback loop :sweat_smile:. Didn't realize it until revisiting again for this post (I put a 4.7uF cap where should be a 47pF). Maybe I copied it wrongly when designing on Eagle, I feel stupid now, hehe.

That capacitor is directly related to the gain of the amplifier. Replacing it should work.

4

Yeah, you are the first person to make a mistake like that. :expressionless:

a7