Ceramic Cap Ripple Current

I'm looking at this cap:

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ND/930704

The only thing the data sheet says about the ripple current is that it is "high".

So -- is there a way to tell just how much ripple current the cap will stand, short of buying 10000 of them and doing a study?

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Reply to
Tim Wescott
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Tim Wescott a écrit :

Don't know but I recently had 'bad' surprises with 0402 x7R caps. Measuring them vs voltage led me to think those were Y5V caps, but those were not. I think I've read somewhere it's related to dielectric thickness.

Y5V being what it is, even in bigger caps, check their value under conditions similar to the final use. You may find lower values X7R will do better. Then you add the temperature effects and...

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Thanks,
Fred.
Reply to
Fred Bartoli

Fred Bartoli a écrit :

When you look at the datasheet p14 you see impedance curves for that very capacitor and min esr is circa 10mR. Now you can you the power dissipation of a 0402 resistor as a start.

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Thanks,
Fred.
Reply to
Fred Bartoli

Hmmm. Y5V. Might be lossy.

Buy 10 and do a study?

There are people that make high-current RF caps. The classic was the ATC porcelain parts, used in RF gear that would melt the solder off regular ceramic caps. Lately they, and others (AVX, Johanson, ATC) are making high-current-rated ceramics. They should have data sheets.

I'd recommend heat sinking the caps to a lot of copper, too. That works for resistors. An 0603 resistor will run happily at half a watt if you solder it to a couple of husky copper pours.

**********************************

John Larkin, President Highland Technology, Inc

jlarkin at highlandtechnology dot com

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Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

Reply to
John Larkin

06ZL-T/587-1352-2-

ttdesign.com

Hi Tim, does this relate to the dissipation factor?

I=92ve always been a bit confused by the difference between ESR and the DF. I got some 10uF ceramics in the other day and gave them the JL, step response test. (10 Volt step from 50 ohm source.)

First here=92s a 10uF tant....(as a reminder)

Step into 10uF tant.

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(so what=92s the little up sloping bit before it turns linear)

10uF ceramic (X7R)

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The wiggles are from my setup. Twice the =91scope vertical gain.

and a 1uF X7R

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George H.

Reply to
George Herold

cap:

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Software

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That's because a tantalum cap is a complex network, equivalent to a bunch of dielectric absorption. The model is multiple RCs in parallel, all with different time constants. The "ESR" then becomes frequency dependent and really has no single value.

You can use the height of the initial step to estimate the ESR of all the equivalent Rs (of the multiple RCs) in parallel.

Some people model a tantalum as a string of cascaded RCs, looking kinda like a lowpass filter, but that's about equivalent.

Needs more gain! The spike is ESL, probably, or test setup leads.

Needs more gain!

**********************************

John Larkin, President Highland Technology, Inc

jlarkin at highlandtechnology dot com

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Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

Reply to
John Larkin

6F106ZL-T/587-1352-2-

is

scottdesign.com

The spike is what's left over from the 40MHz ringies I had before. Now a cap on on BNC jack with x1 scope probe.

Well then it's more than just hanging stuff off the function generator.

George H.

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Reply to
George Herold

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