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design | Capacitance versus voltage for X7S caps?


There are 61 messages in this thread.

You are currently looking at messages 1 to 10.

Capacitance versus voltage for X7S caps? - Joerg - 2010-03-24 19:22:00

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.

Re: Capacitance versus voltage for X7S caps? - Vladimir Vassilevsky - 2010-03-24 19:38:00


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

Re: Capacitance versus voltage for X7S caps? - Fred Bartoli - 2010-03-24 19:53:00

Joerg a écrit :
> 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.

Re: Capacitance versus voltage for X7S caps? - Jon Kirwan - 2010-03-24 19:53:00

On Wed, 24 Mar 2010 16:22:59 -0700, Joerg
<i...@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

Re: Capacitance versus voltage for X7S caps? - Joerg - 2010-03-24 20:40:00

Fred Bartoli wrote:
> Joerg a écrit :
>> 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.

Re: Capacitance versus voltage for X7S caps? - Joerg - 2010-03-24 20:41:00

Jon Kirwan wrote:
> On Wed, 24 Mar 2010 16:22:59 -0700, Joerg
> <i...@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.

Re: Capacitance versus voltage for X7S caps? - Spehro Pefhany - 2010-03-24 21:44:00

On Wed, 24 Mar 2010 17:41:39 -0700, the renowned Joerg
<i...@invalid.invalid> wrote:

>Jon Kirwan wrote:
>> On Wed, 24 Mar 2010 16:22:59 -0700, Joerg
>> <i...@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"
s...@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Re: Capacitance versus voltage for X7S caps? - Jon Kirwan - 2010-03-24 23:17:00

On Wed, 24 Mar 2010 17:41:39 -0700, Joerg
<i...@invalid.invalid> wrote:

>Jon Kirwan wrote:
>> On Wed, 24 Mar 2010 16:22:59 -0700, Joerg
>> <i...@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

Re: Capacitance versus voltage for X7S caps? - Tim Williams - 2010-03-24 23:22:00

"Jon Kirwan" <j...@infinitefactors.org> wrote in message 
news:9...@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 



Re: Capacitance versus voltage for X7S caps? - Ken - 2010-03-25 02:03:00

On Wed, 24 Mar 2010 16:22:59 -0700, Joerg <i...@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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http://web.archive.org/web/20070912104727/http://members.aol.com/sbench102/caps.html
http://web.archive.org/web/20080203162906/http://members.aol.com/sbench102/caps1.html
http://web.archive.org/web/20071107034022/http://members.aol.com/sbench102/caps2.html
 

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