Capacitance versus voltage for X7S caps?

Started by Joerg March 24, 2010
Tried the major mfgs and the typical datasheet looks like this:

http://www.avx.com/docs/Catalogs/cx7s.pdf

Quote "Capacitance for X7S varies under the influence of electrical 
operating conditions such as voltage and frequency."

Then under diagrams ... nada, zip, zilch. Great.

One paper listed X7S with the same voltage coefficient as X7R but that 
doesn't sound right. Anyone have a link to some hard data, with a graph 
in there and preferably no marketing hype?

-- 
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg wrote:
> Tried the major mfgs and the typical datasheet looks like this: > > http://www.avx.com/docs/Catalogs/cx7s.pdf > > Quote "Capacitance for X7S varies under the influence of electrical > operating conditions such as voltage and frequency." > > Then under diagrams ... nada, zip, zilch. Great. > > One paper listed X7S with the same voltage coefficient as X7R but that > doesn't sound right. Anyone have a link to some hard data, with a graph > in there and preferably no marketing hype?
Joerg, Not too long ago I was also looking for C(V) dependencies for different capacitor types; didn't find much useful information either. One of the reasons for that is C(V) behavior of particular cap is strongly affected by electrostatic mechanical (!) effects; thus, at low frequencies, it is too much of dependency from everything. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Joerg a �crit :
> Tried the major mfgs and the typical datasheet looks like this: > > http://www.avx.com/docs/Catalogs/cx7s.pdf > > Quote "Capacitance for X7S varies under the influence of electrical > operating conditions such as voltage and frequency." > > Then under diagrams ... nada, zip, zilch. Great. > > One paper listed X7S with the same voltage coefficient as X7R but that > doesn't sound right. Anyone have a link to some hard data, with a graph > in there and preferably no marketing hype? >
I looked at that recently but for X7R/X5R. Data sheets often have nothing, but the good manufacturers offer some 'simulation' program with lots of curve fitting,... IIRC TDK has some web base one too. I think Kemet, AVX, Murata, Taiyo have what you're after. -- Thanks, Fred.
On Wed, 24 Mar 2010 16:22:59 -0700, Joerg
<invalid@invalid.invalid> wrote:

>Tried the major mfgs and the typical datasheet looks like this: > >http://www.avx.com/docs/Catalogs/cx7s.pdf > >Quote "Capacitance for X7S varies under the influence of electrical >operating conditions such as voltage and frequency." > >Then under diagrams ... nada, zip, zilch. Great. > >One paper listed X7S with the same voltage coefficient as X7R but that >doesn't sound right. Anyone have a link to some hard data, with a graph >in there and preferably no marketing hype?
I seem to recall reading that C0G and NP0 dielectrics have the lowest cap-vs-temp dependance and that pretty much everyone "understands" that X7R dielectrics have large coefficients and are pretty much unsuitable where it matters. They pack a lot of capacitance into a small space and that makes them great for decoupling jobs and not so much else. But I don't know remember reading anything about X7S, specifically. If they are the same as X7R, they are crap if what else I read was right. Jon
Fred Bartoli wrote:
> Joerg a &#2013265929;crit : >> Tried the major mfgs and the typical datasheet looks like this: >> >> http://www.avx.com/docs/Catalogs/cx7s.pdf >> >> Quote "Capacitance for X7S varies under the influence of electrical >> operating conditions such as voltage and frequency." >> >> Then under diagrams ... nada, zip, zilch. Great. >> >> One paper listed X7S with the same voltage coefficient as X7R but that >> doesn't sound right. Anyone have a link to some hard data, with a >> graph in there and preferably no marketing hype? >> > > I looked at that recently but for X7R/X5R. Data sheets often have > nothing, but the good manufacturers offer some 'simulation' program with > lots of curve fitting,... > > IIRC TDK has some web base one too. > I think Kemet, AVX, Murata, Taiyo have what you're after. >
I've been through those. My impression was that a lot of docs I used to see there have been "cleaned out". I need something in the form of a document, not a simulator. Also, other than SPICE and beam field simulators I don't trust them. For example, National has flagged all my first switchmode converter ideas as "can't be done". And all went into mass production without a hitch ... -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Jon Kirwan wrote:
> On Wed, 24 Mar 2010 16:22:59 -0700, Joerg > <invalid@invalid.invalid> wrote: > >> Tried the major mfgs and the typical datasheet looks like this: >> >> http://www.avx.com/docs/Catalogs/cx7s.pdf >> >> Quote "Capacitance for X7S varies under the influence of electrical >> operating conditions such as voltage and frequency." >> >> Then under diagrams ... nada, zip, zilch. Great. >> >> One paper listed X7S with the same voltage coefficient as X7R but that >> doesn't sound right. Anyone have a link to some hard data, with a graph >> in there and preferably no marketing hype? > > I seem to recall reading that C0G and NP0 dielectrics have > the lowest cap-vs-temp dependance and that pretty much > everyone "understands" that X7R dielectrics have large > coefficients and are pretty much unsuitable where it matters. > They pack a lot of capacitance into a small space and that > makes them great for decoupling jobs and not so much else. > > But I don't know remember reading anything about X7S, > specifically. If they are the same as X7R, they are crap if > what else I read was right. >
The lousy ones are Y5V and Z5U. X7R is actually pretty good. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
On Wed, 24 Mar 2010 17:41:39 -0700, the renowned Joerg
<invalid@invalid.invalid> wrote:

>Jon Kirwan wrote: >> On Wed, 24 Mar 2010 16:22:59 -0700, Joerg >> <invalid@invalid.invalid> wrote: >> >>> Tried the major mfgs and the typical datasheet looks like this: >>> >>> http://www.avx.com/docs/Catalogs/cx7s.pdf >>> >>> Quote "Capacitance for X7S varies under the influence of electrical >>> operating conditions such as voltage and frequency." >>> >>> Then under diagrams ... nada, zip, zilch. Great. >>> >>> One paper listed X7S with the same voltage coefficient as X7R but that >>> doesn't sound right. Anyone have a link to some hard data, with a graph >>> in there and preferably no marketing hype? >> >> I seem to recall reading that C0G and NP0 dielectrics have >> the lowest cap-vs-temp dependance and that pretty much >> everyone "understands" that X7R dielectrics have large >> coefficients and are pretty much unsuitable where it matters. >> They pack a lot of capacitance into a small space and that >> makes them great for decoupling jobs and not so much else. >> >> But I don't know remember reading anything about X7S, >> specifically. If they are the same as X7R, they are crap if >> what else I read was right. >> > >The lousy ones are Y5V and Z5U. X7R is actually pretty good.
For low values of "pretty good". I suppose losing 20% of capacitance due to voltage and/or 5% due to temperature and/or a few more percent due to aging is better than -80% or whatever.. NP0 are now available (though a bit pricey and bulky) even in fairly large values like 0.1uF 1206. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On Wed, 24 Mar 2010 17:41:39 -0700, Joerg
<invalid@invalid.invalid> wrote:

>Jon Kirwan wrote: >> On Wed, 24 Mar 2010 16:22:59 -0700, Joerg >> <invalid@invalid.invalid> wrote: >> >>> Tried the major mfgs and the typical datasheet looks like this: >>> >>> http://www.avx.com/docs/Catalogs/cx7s.pdf >>> >>> Quote "Capacitance for X7S varies under the influence of electrical >>> operating conditions such as voltage and frequency." >>> >>> Then under diagrams ... nada, zip, zilch. Great. >>> >>> One paper listed X7S with the same voltage coefficient as X7R but that >>> doesn't sound right. Anyone have a link to some hard data, with a graph >>> in there and preferably no marketing hype? >> >> I seem to recall reading that C0G and NP0 dielectrics have >> the lowest cap-vs-temp dependance and that pretty much >> everyone "understands" that X7R dielectrics have large >> coefficients and are pretty much unsuitable where it matters. >> They pack a lot of capacitance into a small space and that >> makes them great for decoupling jobs and not so much else. >> >> But I don't know remember reading anything about X7S, >> specifically. If they are the same as X7R, they are crap if >> what else I read was right. > >The lousy ones are Y5V and Z5U. X7R is actually pretty good.
X7R is bad enough that it distorts like hell in an audio amplifier (used as the Miller cap) and I know I certainly can't even come close to using them in integrators, from actual (hilarious, for a moment) experience. Decoupling is what they are good for. Jon
"Jon Kirwan" <jonk@infinitefactors.org> wrote in message 
news:9uklq5hjvgr6kjttlagugqd55hfod2gohv@4ax.com...
> X7R is bad enough that it distorts like hell in an audio > amplifier (used as the Miller cap) and I know I certainly > can't even come close to using them in integrators, from > actual (hilarious, for a moment) experience. Decoupling is > what they are good for.
Unsurprisingly, the integration curve (step input) looks just like a high permeability, ungapped ferrite inductor's. You're just tracing out the D-E curve instead of the B-H curve. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
On Wed, 24 Mar 2010 16:22:59 -0700, Joerg <invalid@invalid.invalid>
wrote:

> Tried the major mfgs and the typical datasheet looks like this: > > http://www.avx.com/docs/Catalogs/cx7s.pdf > > Quote "Capacitance for X7S varies under the influence of electrical > operating conditions such as voltage and frequency."
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