The effective capacitance of general purpose ceramic capacitors is a
function of the DC voltage across it. In many cases the capacitance can
drop to less than half of the rated capacitance when you get near the
voltage rating of the part.

The severity of this effect is highly dependant on the specific type of
ceramic capacitor you have - X7R, Y5V, C0G, etc.

For decoupling a 50V part will typically perform "better" than a 6.3V one
of the same type and rating.

See muRata's explanation:
https://www.murata.com/en-us/support/faqs/products/capacitor/mlcc/char/0005

Relevant stackoverflow post "How to derate a ceramic capacitor for DC
bias":
https://electronics.stackexchange.com/questions/280719/how-to-derate-a-cera=
mic-capacitor-for-dc-bias

On Sunday, December 3, 2017, Electron <electron2k4@infinito.it> wrote:

>
> Thank you for all replies. I would like to address one in particular:
>
> Just one question, why 50V? Just because it's very difficult to find 100n=
F
> ceramic capacitors of lower voltage, or 50V specification is truly needed
> (but why? it's a 3.3V circuit after all).
>
> Thank you.
>
> Have a nice sunday,
> Mario
>
>
> At 00:15 2017-12-03, Richard Pope wrote:
> >Mario,
> >     Yes! I won't go in to the reasons why. I bypass the Oscillator
> >and/or oscillators and all of the digital ICs. Linear VRs are also
> >bypassed but look at the datasheet to get the proper values. I mostly
> >use 0.1uF 50V Ceramics. I have at times used 0.01uF 50V Ceramics.
> >Thanks,
> >rich!
> >
> >On 12/2/2017 12:18 PM, Electron wrote:
> >> Hello,
> >> it may seem a banal question, but as it's the first time I use an
> external
> >> oscillator (with integrated crystal), I am not sure. The datasheet
> makes no
> >> mention whatsoever to the need to use a bypass capacitor in the power
> line:
> >>
> >> https://global.kyocera.com/prdct/electro/product/pdf/clock_k_e.pdf
> >>
> >> But is this truly the case?
> >>
> >> Should I put a (100nF?) bypass capacitor anyway in your opinion?
> >>
> >> Space on the board may be used for something else otherwise, so I don'=
t
> >> want to put useless components. But then again who does.
> >>
> >> Also, I guess there's no advantage in grounding the metalcase on this
> >> integrated oscillator, like I use to do with Xtals. Maybe it's already
> >> grounded but I haven't received it yet.. I ask in case it's not.
> >>
> >> Thank you.
> >>
> >> Kind regards,
> >> Mario
> >>
> >
> >
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