Author Topic: USB connector GND pin, ferrite bead yes or no?  (Read 3784 times)

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Offline KarelTopic starter

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USB connector GND pin, ferrite bead yes or no?
« on: August 28, 2017, 03:14:29 pm »
In this application note:

https://www.silabs.com/documents/public/application-notes/AN0046.pdf

They say you should use ferrite beads for the GND pin of the USB connector. When I did that, I had an unreliable connection.
I could only solve it by bypassing the ferrite bead. Since then I always connect both the GND pin and the shielding of the USB connector
directly to the groundplane. After that, I never had any problems in all our projects.

What is your opinion on this?

 

Offline Neilm

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Re: USB connector GND pin, ferrite bead yes or no?
« Reply #1 on: August 28, 2017, 07:27:02 pm »
Personally, I wouldn't put an inductor in the 0V line. If there is any issue, I might have a small ferrite over all the lines but that wouldn't be all that often.

In regards connecting the shell to 0V that will depend on the product I have designing. If I have a double insulated unit I tend to connect it, if I have an earthed metal box I would connect to that not the 0V. Generally, I leave a couple of pads to allow me to connect or not connect it depending on fitting components - that way I don't have to respin the PCB
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Offline Scrts

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Re: USB connector GND pin, ferrite bead yes or no?
« Reply #2 on: August 29, 2017, 02:58:57 pm »
I find those ferrites on GND signals to be useless. It brings more issues than solutions.
 

Online wraper

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Re: USB connector GND pin, ferrite bead yes or no?
« Reply #3 on: August 29, 2017, 03:35:26 pm »
Unless connector is connected to the grounded metal case by EMI springs or conductive foam, I would certainty avoid splitting the ground. Otherwise shield in the cable no longer functions as shield at high frequencies.
 


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