questions about Leonardo Standalone


I started to play with the leonardo board, after few years of Atmega328, i have to admit that it offer very interresting possibilitys. So i planned to make a standalone one!

I made before several UNO standalone, but i am not sure i understand in this case every part of leonardo schematic :

How does a CG0603MLC work? it seem to protect from electrostatic discharge, but i am not sure what that mean..

Why is there a MH2029 on the AVCC connection?

The quartz model is different, he need two pins link to the ground.. does this make a real difference compare to a normal 16MHz quartz?

thanks, don't hesitate to ask question as well if you are making the same project :slight_smile:

CG0603MLC is a multi-layer varistor device - above a threshod voltage is starts to conduct
heavily to protect devices from over voltage.

MH2029 is a ferrite bead for EMI suppression or power line filtering (as here). Ferrite beads
work like an inductor but are usually good to 10's of GHz unlike coils.

There are several low-profile surface mount crystal packages that are used for both bare
crystals and also for self-contained crystal oscillators - the later require 4 pins so thats what
the packages generally have. The package has no effect on the crystal behaviour except in
electrically very noisy environments when a grounded case for the crystal helps protect it
from interference.