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?
Could you specify more information, such as load conditions per port, source port info, etc?
One way you might solve this is to use LTSpice or similar simulator to play around with various loads and filtering capabilities.
LC filters can be effective, but the current can require a very large inductor. The larger the inductor, the smoother the current ripple. You may consider adding a TVS shunt for any spikes.