On Sat, 06 Feb 2010 13:08:43 -0800, Mycelium
wrote:


Sure they are 10 and 22uF MLCC's (X5R) are used all the time in the
output of SMPS's so they do carry large RMS currents. That cap looks
like a large 1206 or bigger package which means it's probably a 10 or
22uf cap.

No, ya dippy dope, that is NOT a 22uF cap! That is more likely a
standard 0.01uF cap.

Now, re-do using the right math.

We were both wrong twit as the OP stated it's a high voltage 20pf cap.

The math involved is beyond your limited abilities. Oh sorry I just
read your other posts. You're an expert solderer yielding better
results then NASA certified machine soldering.

You are attributing storage cap nomenclature and specs with ceramic
caps, which have entirely different purposes and operating spec
declarations.

If your SMPS is switching at 500kHz are faster you don't need large
Aluminum's for hold-up in between such small switching periods.

You are still in the wrong realm.

From just one of the numerous application notes out there on MLCC's as
output caps for SMPS's.

No... as filtration on the outputs, not as the storage itself, and in
the cases where it is "the storage cap", it is usually a high voltage
application, where the output is in mA.

"Because the ESR of ceramic capacitors is low, the capacitor
temperature rise due to ripple current dissipation is usually
negligible.

Oh, boy... you are good at quoting. You are apparently not that good
at interpreting what you are reading.

You're useless at interpreting what you're reading. My comments were
in regard to ceramic output caps on SMPS which is stated several times
in my response. Did you miss that little tidbit you illiterate piece
of ****.

I'm not the one having comprehension problems. You stated that
Ceramics aren't meant to handle large rms currents and I said nicely
yes they are. Now I'll say it not so nicely you're full of **** yes
they are and are used all the time to do just that.

Good design practice dictates that we always confirm this
and verify that the output capacitor RMS current and temperature rise
are within the manufacturer's suggested limit.

That cap in the photo is NOT an output cap in ANY circuit, you dippy
twit!

Given the OP didn't say the application where it is used or anything
other then the cap failed on a mobo an honest mistake. No need to get
belligerent.

The maximum RMS ripple
current seen by the output capacitor occurs at the maximum input
voltage…."

No ****.

Sounds to me like they are working while they carry high rms current.

Sounds to me like you are lost in a lost world as it relates to the
application that cap is being used for, much less its value, idiot.

I don't think you know what the output caps on an SMPS do idiot.What
do you think is supplying the current to the load when the switch is
off? How do you think the cap gets recharged I think they call that
rms ripple current. Or is there some other NASA bullsit term for it.