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RE: Deep Dive into ESR, Testing

clem57 — Wed, 14 Aug 2019 19:25:26 GMT

Nice report. I [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-43442c32-4147-4bba-85ac-c539f9af7993/contentimage_5F00_3708.png:16:16] the graphs. It takes time to collect all the points.

Thumbs up.

Clem

RE: Polymer Cap Charge Pump

dougw — Thu, 18 Jul 2019 23:24:32 GMT

Also added an unboxing video of the finisher prize - thanks element14 and Panasonic.

RE: Capacitor Leakage Current over Temperature

shabaz — Wed, 26 Jun 2019 18:36:47 GMT

Hi Michael,

Very interesting results!

Recently I took a look at a couple of computer motherboards, to see if I could spot any trends. One was an old motherboard (2010), and the other was about 5 years more recent in manufacture. They were from different manufacturers, both major brands, and both intended for server use, not consumer.

The older motherboard had (as expected) lots of MLCC, and the remainder were a mix of aluminium polymer, some tantalum (clustered in one part of the design only, near some connector), and some aluminium electrolytic. There were also some I could not determine (rectangular case like tantalum, but all black in colour, they may have been tantalum polymer - I could not tell from the code on top).

The newer motherboard had the MLCC as expected, and then _all_others were alu polymer, save one, which was aluminium electrolytic. There were zero tantalum. The lone alu electrolytic (Nichicon HM series) was at a corner of the board, perhaps it was decided it would run cool and have a long life there. It was part of the output of a DC-DC converter, in parallel with some MLCC. The DC-DC converter chip was the same as that used in a few other places of the board, but the other places used alu polymer in parallel with some MLCC. (EDIT: it was 1000uF 16V, so perhaps that DC-DC converter has a higher voltage output, for some ancillary purpose not as power-intensive as the lower-voltage output DC-DC converters on the rest of the motherboard).

It was interesting seeing the complete absence of tantalum, at least for that server motherboard, and near-absence 10 years ago. For a different market (with ultra high reliability requirement) out of uni, the capacitors were almost entirely tantalum (+ MLCC), no alu electrolytics.. but then there there were no alu polymer available at the time.

RE: Capacitor Leakage Current over Temperature

neuromodulator — Wed, 26 Jun 2019 16:54:29 GMT

Very nice report Michael, the chamber and the parallel recording through a DAQ surely help a lot in making the testing much more rigorous!

I'm currently working on designing a chamber to do what you just did, test different arbitrary temperature curves...

To reduce noise I set the number of power line cycles to 2, and averaged 100 measurements, this took approximately 3 s.

In the plots, which is current, the red or the blue? What is the other color?

As there appears to be hysteresis, it would be interesting to see an i vs T plot.

To see the effect of the dT/dt it would also be interesting to test different values of dT/dt.

RE: Capacitor Leakage Current over Temperature

genebren — Wed, 26 Jun 2019 15:18:15 GMT

Very interesting tests and data. I look forward to your further tests and conclusions.

Gene

RE: Results and conclusion

three-phase — Thu, 20 Jun 2019 20:52:45 GMT

Interesting set of results to your experiments. I have been wondering why the Polymer capacitors appear to be running warmer than electrolytic in my amplifier circuit. I think some more experimentation is required.

Kind regards.

RE: Results and conclusion

shabaz — Thu, 20 Jun 2019 15:53:23 GMT

Very interesting results!

I wonder if some of the short-term fluctuation (not the overall trend) in the hybrid capacitor leakage current measurement is due to electrolyte moving inside (no idea, just a guess!).

[View:/resized-image/__size/620x360/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-55ed5e6a-14ce-4cb0-b11a-72d1838c3373/5850.contentimage_5F00_206654.png:620:360]

It's great to see that these types of measurements, and greater scrutiny and understanding of components, are achievable nowadays with modern not crazily-expensive equipment!

RE: Results and conclusion

michaelkellett — Thu, 20 Jun 2019 08:12:28 GMT

Nice report and a lot of work. Can you post any pictures, and explain how you controlled and measured temperature (I'm looking for a reason for the leakage leading the temperature.)

!!!

Just seen your other blog which does exactly that - thanks. (But how to explain your actions leading my comments [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-55ed5e6a-14ce-4cb0-b11a-72d1838c3373/contentimage_5F00_1.png:16:16])

And now for the explanation - challenges welcome !

I think your thermistor and capacitor are thermally well linked - so the temperature of the capacitor will be close to what you think.

It's fairly clear from looking at your graph that the peak leakage current happens when you have the fastest rate of temperature rise.

So I think that to measure the real leakage current the temperature has to be stable .

But - your experiment adds a great deal to knowledge (mine at least) because it makes clear that the effective leakage current of

a capacitor in an application where the temperature is changing may be much higher and much more variable than I would have

expected.

That is something I had not thought about (or recall seeing any reference to) so thanks a lot !!!

RE: Results and conclusion

aspork42 — Wed, 19 Jun 2019 23:19:44 GMT

Nice job on the tests! You got some real world data here to consider. Yeah - these tests can be challenging to set up accurately when doing semi-manual data collection. You could have considered using relays or even transistors to short out the terminals, but that presents its own challenges.

RE: more than you expect!

colporteur — Tue, 11 Jun 2019 19:47:41 GMT

Enjoyed the extended testing. Great to see vendor provide the product samples.

Sean

RE: Evaluating Polymer Capacitors - Buck Converter Tests

14rhb — Fri, 07 Jun 2019 19:43:58 GMT

Hi Ralph,

I'm having a look to see what everyone else got up to on this challenge, your work here is really interesting, especially as you explore the buck circuit (and mine was a boost). A very interesting conclusion as well e.g. that the ESR can actually be too low and cause instability....something I hope to remember for future designs.

Rod

RE: Blog 2: As much as Polymer Capacitors can go in Instrumentation Amplifier.

michaelkellett — Tue, 04 Jun 2019 08:14:39 GMT

You might like to consider what useful purpose C1 has in this circuit and with the values you have chosen for C1, C2 and C3 and R1 and R2.

Because C2 and C3 are both connected to ground their series value shunts C1 - so why not remove C1 completely and increase the value of C2 and C3 to keep the impedances the same.

Alternatively increase R1 and R2 and keep C2 and C3 = 4.7uF to keep the filter response the same.

Now you can do your test without using a huge MLCC.

I must point out that this is not a rational way to test these capacitors - the 4.7uF POSCAPs have a claimed ESR of 0.3R and you have series resistors in your design of 10R -

so a change in cap ESR of 100% will make a difference of about 3% to the cut off frequency of the filter, but the tolerance on capacitor value is 20% and will swamp this small effect.

RE: Using Polymer Capacitors for Supply De-coupling in the Current Amplifier

shabaz — Fri, 31 May 2019 10:48:48 GMT

Hi Donald,

Excellent blog post and project, and as [mention:f80b53cee57c44bc9d7c577d07d7c791:e9ed411860ed4f2ba0265705b8793d05] says that's a really nice set-up!

By co-incidence, for a project I'm working on, I've been looking at Panasonic SEQP too, it's fantastic being able to design with a capacitor that is far cheaper than tantalum, and possibly won't degrade like old alu electrolytics. The low ESR is nice too, and I'm going to parallel it with an MLCC too, and it will form the input power entry portion of the board. I like that they come in 10V versions, so I'm going to use that for 5V power entry, so that there is some voltage derating too (not sure how much is recommended). Also, [mention:a5312e9762dd4699ba5d3876da34ffe5:e9ed411860ed4f2ba0265705b8793d05] made an observation about reverse voltage w.r.t. polymer caps, so the power entry portion will have space for a reversed diode too just-in-case (since my project does not have a transformer supply directly permanently connected as in your case).

RE: Using Polymer Capacitors for Supply De-coupling in the Current Amplifier

jw0752 — Fri, 31 May 2019 02:24:14 GMT

Hi Donald,

It is great that you are using this experiment to expand your knowledge and experience with the previous project. I am interested in reading your results. Your test board is very impressively organized.

John

RE: Deep Dive into ESR, Testing

phoenixcomm — Mon, 27 May 2019 00:34:49 GMT

Frank Great Stuff! This was a very informative module, your explanation helped me a lot. I don't remember covering ESR back in my College EE courses, but then I am getting older and have CRS (Cant Remember ***). So I am constantly looking in a book or on-line for answers. Which is the definition of an engineer ie. If you don't know the answer, you know ware to just look it up.