Capacitance versus voltage for X7S caps?
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From: Joerg on 24 Mar 2010 19:22 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.
From: Vladimir Vassilevsky on 24 Mar 2010 19:38 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
From: Fred Bartoli on 24 Mar 2010 19:53 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.
From: Joerg on 24 Mar 2010 20:40 Fred Bartoli wrote: > 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. > 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.
From: Tim Williams on 24 Mar 2010 23:22
"Jon Kirwan" <jonk(a)infinitefactors.org> wrote in message news:9uklq5hjvgr6kjttlagugqd55hfod2gohv(a)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 |