I'm working a a board that will need 5V and 3.3V inputs (about 500 mA), and I'd like to (due to simplicity) use a 9VDC wall-adapter for its input. I've not decided if I'm going to use a linear or a buck converter for it. The board will have a few analog amplifiers, a battery charger, and a microcontroller.
Is there a general guidance for what sort of filtering there should be at the power input? I tried searching this forum, but didn't find anyone talking about how to filter DC input.
I found a design that looks reasonable in this
automotive power supply project on HACKADAY. (see attached)
Some thoughts of mine:
- Is this overkill, and I should be able to use only a fuse and schottky diode, and I should just add ferrite beads/inductors if I notice problems?
- Should the fuse be closer to the DC input jack, so that things don't fry if the capacitor shorts?
- Should I add another 100nF capacitor on the input side of the inductors?
- How do I choose which ferrite bead to use? Is larger impedance at 100 MHz generally a good thing? Or would I need to do full EMC testing to know which one to use. (I know I need to look at the current and max DCR ratings, but there are still many choices.)
- Should I be using a common-mode choke in addition to or instead of the ferrites?
- Is it common to add some over-voltage protection, like a zener diode past the fuse?
- Are there existing designs that I should copy?
Thanks!