USB Circuit with ESD Protection – Correct Implementation

esdesp32usb-host

I am trying to make a breakout board with the ESP32-S3-WROOM-1 and wish to try out some of the USB-OTG examples. In the schematic of the chip I am using there only seems to be 2 capacitors tied to D+ and D- but I am not sure what the values need to be. I then turned to the schematic of my S3-WROOM-1 Devkit module and it only has these diodes tied to D+ and D-. I decided to try and implement it similarly for D+ and D- only as I don't intend powering OTG devices as mine are self-powered. I just wish to know if I did it correctly along with the layout of the pcb. If it will work with the capacitors only as well that would be fine as well and would just require the values as Im unsure.

ESD Diode

From S3 Datasheet:

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From: S3 Devkit datasheet:
enter image description here


My versions:
enter image description here
enter image description here

Best Answer

Yes, it is correct. I built a similar one and it works very well

Link to the entire project, schematics, layout, etc: https://github.com/crgarcia12/electronics-homeassistant-lightscontroll

Something you might consider

  1. Using a usblc6 instead of individual diodes: https://www.st.com/resource/en/datasheet/usblc6-2.pdf enter image description here enter image description here

  2. Double check if connecting the Shield to GND is what you want to do, specially considering you have an external source (is it floating GND?) I usually do it using a very large resistor instead. This will allow voltage to match, but protect in case there is a spike or any differential. I believe the general recommendation is to not connect them at all, but since you have ESD to GND, it might be better to connect them using a resistor instead.

  3. Since you have space, you can add a resistor in series or a probe-point, to connect a logic analyser or an oscilloscope in case there are problems. This have been very useful to me.

  4. Make sure you read the ESP placement guidelines. For example, make a cut-out under the antenna if you can. If you cannot, do not place any copper under it in any layer (I can't see properly your picture, but I think you are even sending 3V under it)

  5. The capacitors have to be very small value. In all my tests it works fine without them

This is my ESP-32 S3 version (link): enter image description here

And this my ESP-32 version, with individual diodes instead: enter image description here