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Why is the shield connected using a ferrite and capacitor? #11

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crgarcia12 opened this issue Oct 3, 2022 · 1 comment
Open

Why is the shield connected using a ferrite and capacitor? #11

crgarcia12 opened this issue Oct 3, 2022 · 1 comment

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@crgarcia12
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Thanks a lot for sharing this design! Super useful!

I never saw the USB Shield connected to GND the way you did it. Could you please help me understand why you did it this way?

I want to mirgrate my ESP32-Wroom-D based board to the S3 (https://github.com/crgarcia12/electronics-homeassistant-lightscontroll).
I read a lot about the USB shield on the internet, but it seems there is no consensus on what to do with it. In my case, I ended up connecting it to GND via a resistor, but in practice it worked with or without the resistor (I'm using an isolated PS)

Thank you!

@eggsampler
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eggsampler commented Oct 27, 2022

This is just a filter for the shield connection. It's not based on anything other than observations. They can be entirely omitted and that won't be a problem for a majority, if not all, use cases. Adding a resistor, even a 0 ohm, can add a bit of support if you experience any ground bouncing, or small bit of inductance for filtering. But realistically you probably won't need it.

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