Hello guys i was looking over the schematic for the Leonardo Pro Micro using the Atmega32u4 and i just have a quick question. Are all 3 of those capacitors on the output of the voltage regulator really necesary? Ive always just used a 10uF capacitor on the output of my 3.3V regulator.
Hi.
The micro Farad capacitors are used to filter out larger deviations, the smaller capacitors are used to filter out spikes.
Although the capacitors are drawn directly next to the regulator, their position on the board is likely to be somewhere else.
Have a look at this picture from the Sparkfun site who originally designed this one, and find the capacitors:
You might find the two polarised capacitors on either side of the regulator, as drawn in the schematics.
I can't tell exactly where the others are as there are a few more capacitors on the board, but you can see they are all over it.
If you want to know where they are exactly, go to the Sparkfun site, and download the Eagle files.
And install Eagle if you haven't already, so you can view the board layout and find where the capacitors are.
So, next to your 10 micro Farad capacitor, it would be good practice to use some additional capacitors in the nano Farad range.
And put one as close as possible to any IC and / or main part of your design.
"Ive always just used a 10uF capacitor on the output of my 3.3V regulator."
Depends on the regulator. Look up the datasheet for both, see what's recommended. Some need caps on both input & output for stable regulation.