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The MLCCs in 0805 case seem to have one or two orders of magnitude higher ESRs at that frequency. Are there any such low ESR caps out there, preferably 0805 MLCC but not compulsory? It is a 220 nF cap I am after.

edit

My datasheet does not hint to polarity though. How would I be using an electrolytic? I suppose solid aluminum would also be better.

enter image description here

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  • \$\begingroup\$ Yes the ESR at 100 Hz is surprisingly high for ceramic. \$\endgroup\$
    – user57037
    Jun 30, 2020 at 23:47
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    \$\begingroup\$ Did you look at aluminum electrolytics by any chance? \$\endgroup\$
    – user57037
    Jul 1, 2020 at 2:46
  • \$\begingroup\$ @mkeith care to look at the edit ? Thanks \$\endgroup\$
    – kellogs
    Jul 1, 2020 at 7:24
  • \$\begingroup\$ They clearly expect you to use a ceramic cap. Just use one that fits in that location. You could take a look at other types of caps that use some type of plastic insulator. Question: where did the 100 Hz part of the spec come from? Ceramic caps may have very low ESR at higher frequencies. \$\endgroup\$
    – user57037
    Jul 1, 2020 at 18:17
  • \$\begingroup\$ You may be over-thinking this. \$\endgroup\$
    – user57037
    Jul 1, 2020 at 18:18

5 Answers 5

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0.22uF SMD Do not expect max 200 mOhm ESR easy to find or inexpensive.

Also ESR can change with frequency in some materials like metal film.
If they only specify D.F. specified @ 120 Hz e.g. e-caps 0.1% of 6kOhm is 6 ohms.

Since Frequency is not specified, that makes this requirement vague.

I might choose Metal Film to achieve this which the added benefit of non-piezo-electric. D.F. reduces with rising f in MF and thus can be 200 mOhm @ 1 MHz for example. e.g. type FCA Cornell

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  • \$\begingroup\$ I asked them to clarify on the frequency and it turns out to be output data rate, which in my case is 100 Hz. I asked again for a 200 mOhm cap example at that frequency, they jsut brushed it off telling me these caps are very common and sent me off to google.com :) \$\endgroup\$
    – kellogs
    Jul 1, 2020 at 12:09
  • \$\begingroup\$ OK, FCA Cornells are 0.015 tan_delta @ 1 kHz which equates to ESR = 1.08 Ohm @ 1 kHz. So... probably worse at 100 hz. Best film cap (not metal film, just film) I could find was 0.8% tan_delta @ 1 kHz - still lacking... anything better than these ? \$\endgroup\$
    – kellogs
    Jul 1, 2020 at 12:43
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    \$\begingroup\$ It is the pulse duration that determines the rise time and frequency of interest for ESR. Thus you do not look for ESR @ 100Hz but probably 1Mhz. The distance is <10nH/cm for trace path so keep close to avoid lowering series resonant f. \$\endgroup\$
    – Tony Stewart EE75
    Jul 1, 2020 at 15:04
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    \$\begingroup\$ I estimate that from a worst case risetime= BW=0.35 /T 10~90% \$\endgroup\$
    – Tony Stewart EE75
    Jul 1, 2020 at 20:20
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    \$\begingroup\$ Yes the bandwidth of the edge in a square wave is not determined by the wave frequency. It is determined by the rise time of the edge. \$\endgroup\$
    – user57037
    Jul 1, 2020 at 21:57
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I don't know why you want the ESR to be 0.2 ohms at 100 Hz - it does not say the frequency on the datasheet.

And at least ST does not use capacitors with those specs on their eval boards.

On one eval board for that chip they have TDK C0603X7S0J224K030BC there. Another eval board has Multicomp MC0603B104K500CT there, and it's bog standard 100nF.

Just put a 220nF 0805 X7R capacitor there, however, you might want to choose one with large enough voltage rating, e.g. 50V, so that any DC bias does not derate the capacitance.

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There are clearly much higher frequencies than 100Hz involved in C1:

The following recommendations apply to capacitor C1:

It must be connected as close as possible to pins 5 and 6 since very high current pulses flow from C1 to pin 5 and 6. This avoid problems caused by inductive effects due to the length of the copper strips.

It is highly recommended to use low ESR (max 200 mOhm)

If they are talking about negating the inductance of a few mm of traces, it is hundreds of MHz or more. It also doesn't make much sense in the context of a bypass capacitor to worry about ESR on something that has an Xc of thousands of ohms, as Tony points out.

I suggest using Murata's simsurfing tool, which gives individual characteristic curves for each part number. For example, this is an 0402 part 220nF which shows an ESR of < 200m\$\Omega\$ from 200kHz to more than 1GHz.

enter image description here

However, keep in mind that (especially smaller parts) can have a wicked voltage coefficient. At 3.3V this one isn't too bad, but at the rated 10V it pretty much disappears.

enter image description here

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Yes, you should be able to find what you are looking for.

I can't give you a specific example, because then this would be just a shopping question. Shopping questions are not allowed here.

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  • \$\begingroup\$ For what purpose? \$\endgroup\$
    – Bruce Abbott
    Jun 30, 2020 at 23:33

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