Sunday, 31 August 2014

USB 5v power filtering


I am creating a pcb that splits a single USB input into 3 outputs (one with data/power carried, two with just power), and I was wondering what is the best way to reduce noise on the power line as this is being made for a low noise environment (for radio work).


I currently have a simple capacitor on the vcc/ground which would reduce the noise a bit, but is there a better way? I have read about LC filters and it seems this would work better than just a plain capacitor. Does anyone have some values that of common inductors that I can source out to add to my project to reduce DC noise on the USB power?



I also have switches which open/close the power outputs and I am worried about voltage spikes when you go to turn on the hardware. Is it possible to filter these by placing a capacitor in parallel to the switch output and ground?


Finally how may I add protection to the circuit to protect the hardware in case of a failure of the pcb? I was thinking about adding a diode for some form of over voltage protection but I am worried about the voltage drop.


Thank you for your time and any answers you can give me.


edit:: Been watching more and more videos mostly relating to quad copter noise filtering for their wireless camera systems. It seems that generally the larger the inductor the better, although a 400-600uH inductor seems to work well with a decoupling capacitor. Does anyone have any other input of the size of inductor that would work to filter most of the noise on a USB power connection?




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