Capacitor's ESR and ESL calculations

Hello I found many datasheets in internet, but no one has ESR and ESL ! where else can I find them? I want values of ESR and ESL for a 1000VDC, 47nF Capacitor. does anyone has any datasheet containing these values?

Forget equations - they should both be in the data sheets as numbers. Just add them in series with your capacitor model. They will be manufacturer-specific, so an equation wouldn't be of much help anyway.

d

Pearce Consulting

Are you sure? It may be there in graphical form of impedance vs frequency. The minimum value on the curve will be the ESR, and the frequency at which it occurs will give you the inductance.

Give us a URL for one of these, and we can see what is there.

d

Pearce Consulting

You would need to give a lot more data. These figures are dependant on the 'structure' of the capacitor, and are normally published as part of a complete 'table', in the full sheets for the capacitors. Capacitors from 'brand name' manufacturers, normally have this data readily available, but normally as a 'table', in the 'structure' data, rather than listed with an individual data sheet. So (for instance), if you look at:

This has the sheet for some of the Sanyo capacitors, and also lists X5P, and X5U ceramic capacitors for comparison.

Best Wishes

I read in sci.electronics.design that snipped-for-privacy@yahoo.com wrote (in ) about 'Capacitor's ESR and ESL calculations', on Fri, 17 Dec 2004:

It may not work for electrolytics and hi-k ceramics, but for other types of cap you can calculate ESR from the tan [delta] figure usually given in data sheets. BUT it may only be valid around the frequency at which tan delta was measured.

tan [delta] = ESR/Xc = ESR/(2[pi]fC)

ESL is about 1.6 nH per millimetre of distance between the points where the cap connects to the rest of the circuit. If, and only if, the cap is well-designed.

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Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
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Why not just measure them? It's not rocket science.

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AVX has detailed info on their capacitors. The following link has all sorts of info that you're looking for.

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Mark

go look at the TDK website. they have detailed models for their ceramic capcitors, in a PDF.

Cheers Terry

because I just want to simulate them in orcad capture

For example, in the following URL can you tell me ESR and ESL of any of

47nF (with Voltage 1000V or more) Capacitors? Should I also tell you the frequency?

For a high-voltage film or ceramic capacitor, yes! ESR is a concept reserved primarily for electrolytic capacitors, in the 100kHz to 10MHz region, which is why you don't see data for your type of capacitor. As you'll see from the following RF-style analysis, a datasheet spec wouldn't have much meaning.

The relevant parameter for a high-frequency capacitor would be the quality factor, Q. As it happens, Q and "esr" are related, Q = Xc / esr. A high-Q capacitor's Q usually decreases with frequency, for two reasons. First, capacitive reactance goes down with frequency, Xc = 1/2pi f. Second, esr goes up with frequency due to eddy-current skin-depth losses.

At modest frequencies, ~ 50kHz to 1MHz, a small cap's Q may be over 1000, but at higher frequencies it may drop to 50 or less. Larger caps may have much lower Q than small ones.

As for ESL, for many film and ceramic caps that's given almost entirely by the leads and the wiring configuration (the latter effect is dominated by the enclosed area in the wiring loop). For example, your 47nF would look like j3.4 ohms at 1MHz. If this cap were to have a Q of 200 at 1MHz, it's esr would have to be 3.4/200 = 0.017 ohms. If your cap's wiring had a total lead inductance of say 15nH, that'd be 2pi f L = -j0.090 ohms of inductive reactance, more than the cap's esr at 1MHz. A quick calculation shows your wired-up 47nF cap would resonate at 6MHz, where the Q might still be > 50. But if you bypass this with R = 2pi fc L = 0.56 ohms or less, that'd nicely kill the resonance. As it happens, an electrolytic cap has such an esr, hence the recommended practice of using at least one of these on your circuit board along with the 0.1uF bypass caps.

--
 Thanks,
    - Win

? d

Pearce Consulting

Hey, Rich, I hear the Apostasy Police pay better.

Best regards, Spehro Pefhany

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Sorry I mean the following link:

You are undoubtedly referring to the 'Postrophe P'lice.

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