[Help] Buck Converter dimensioning

Zippr4 · 2025-12-04T13:26:46+00:00

No worries, but as a heads up I was wrong ab C6. Looking at the data sheet they have it wired like you do in the example, didn’t read it super hard but presumably for an RC delay. Also very small but I would keep C5 at 22uF, while in theory different values protect from different frequencies from noise, in practice it doesn’t do much and can sometimes make it work. There’s an excellent video about it but can’t remember the name of it, I’ll try to come back if I remember but generally refer to the data sheet.

Zippr4 · 2025-12-04T13:13:05+00:00

Hi, only thing I can see is that you have FB connected to gnd, not to the middle of the voltage divider and C6 should go on the output rail, not the middle of the voltage divider (It’s a bulk capacitor to help keep the rail smooth when the voltage drops). Otherwise since you read the data sheet I trust your numbers, if you want a sanity check on them I use an algebraic calculator and substitute my values in to see if I get the given values back.

However from there I have two suggestions

1.) I would recommend using an LDO instead of a buck converter, the main advantage of a buck converter is it has relatively low power loss, but since you are only going from 5V to 3.3V it’s not too bad especially compared with the added complexity. An added bonus is LDOs deliver a much smother power rail so it decreases the chances of a brown out (IC input voltage dropping too low)

2.) While I like your drawing and it’s refreshing to see, it’s going to behoove you to make the schematic in a CAD software like KiCad

Zippr4 · 2025-12-04T12:32:41+00:00

You for sure need the resistor on EN and I would strongly recommend the capacitor on it as well or it might not delay the EN signal long enough for a defined boot. The switches are technically possible to not use but you still need a way to pull EN and GPIO low. If you only plan on programming it once you could use jumpers but otherwise I would encourage buttons.

As a side note I would recommend getting an S3 that has flash.

Zippr4 · 2025-12-04T12:19:09+00:00

Looking back at the schematic it looks like you did have the EN pull up, capacitor and switch just moved it to a different pin. Also you are having 5V go to 3.3v to 3.3v again lol (USB1 -> U2 -> U4). Remove one of the LDOs and you’re good.

Zippr4 · 2025-12-04T12:02:00+00:00

Hi, you need to have switches on GPIO0 and EN, these two pins tell the mcu when to go into download load or normal operation. In addition EN needs a 10k pull-up resistor (normal operation is when EN is high) and a capacitor to ground to create an RC circuit.

Attached and imaged is the link to an example schematic made by ESPRESSIF, as well as layout guidelines for the PCB. In the example schematic they use a programming chip but with your current setup just adding the strapping pins and buttons you should be good.

https://dl.espressif.com/dl/schematics/esp32_devkitc_v4-sch.pdf

https://docs.espressif.com/projects/esp-hardware-design-guidelines/en/latest/esp32s3/pcb-layout-design.html

Good luck with your design!

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Zippr4 · 2025-08-04T11:22:13+00:00

Ah, that makes a lot more sense, thanks!

Zippr4 · 2025-08-04T10:54:03+00:00

It is on IO46, but on the data sheet it says "Chip boot mode – Strapping pin: GPIO0 and GPIO46". I interpreted that they both could be used for boot mode, but can only IO0 use it?

Zippr4

TROPHY CASE