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Filtering USB input.

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Onedust

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Greetings to all,

I have a question regarding using USB Power Adapter as a Power supply. I am using following module as a part of my HW design: **broken link removed**. It really lacks information in datasheets. The only thing it has on power supply requirements, is that it requires 5V+/-5% (https://www.fs-net.de/assets/download/docu/efus/efusA7UL_Hardware_eng.pdf, page 25). I guess this module has some kind of power regulator on it, but I have zero info on it.

I've contacted tech. support and they told me that the module doesn't have any particular start-up requirements (such as "supply voltage rise time". I am really conscious of UVLO, had pleasure debugging it once), apart from the start should be "more or less" continuous. Well it's all nice, but I would like to be sure that everything works fine, so my question is:

I know that my customer is going to use a USB power supply adapter, but I have no idea which one. It can be even some cheap Chinese one, the only info I have is that it will be capable of 2A. How would you suggest to filter USB input to be on the safe side? I've attached a pdf with a snippet from my power supply schematics(don't mind my notes). Would this filter be enough? How do you usually filter USB input? It should be more like a rule of thumb, since I have basically no info on the efus module and on the USB power supply, which is kind of annoying. So please don't start with "you have to give us more info", I don't have it myself:(

Any suggestions or links to info on the subject are very welcome.

Kind Regards,
Den
 

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  • USB_PWR_SUP.pdf
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Check the Switching frequency and ripple frequency caused by TPS82084. You should use a filtering of atleast 10times switching frequency. You can also use a TVS in case of a surge appear(ESD).The Raspberry Pi uses a SMBJ5.0A device to suppress transients.

You may need to put the ferrite bead to separate the ground also.
 

TPS82084 is not a typical Switching Regulator, it is an integrated module, it doesn't have to be heavily filtered on both sides against 2.4 MHz (its sw frequency). So there is no worry there. My problem, as I asked before, is the USB input which goes directly to efuS Module, NOT regulators, they are fine as they are. I don't know how noisy the USB power supply adapter will be. And i dont have any experience with USB power supply adapters in general. Therefore my questions to you - guys with experience :)
 

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