Modern polymer\tantaum capacitors - Page 1
Forum section: electronics / projects

author: VEGETA
author_rank: Super Contributor
timestamp: March 27, 2025, 10:55:04 pm
content: Hello,I made a rev2 of my psu design using modern TI DCAP3 switchers using only ceramics and it worked flawlessly... i used one 22u panasonic polymer cap (OS-CON 35SVPF22M) which has 35mR DCR.However, i saw other forms of modern caps by panasonic... namely POS-CAP and SP-CAP which support low esr (30-40 mohm and less for higher capacity) and my question is: are they worth it?i mean, instead of using multiple ceramics in parallel (after compensating for dc bias, and ensuring voltage is the same), is it worth it to use one or 2 of these? or regular OS-CON caps?multiple ceramics in parallel would result in smaller esr but at 40 mohm is already small enough... still, don't know about current capability of these 2 solutions and the effect on ripple and so on.please share your opinion.thanks !

author: Kurets
author_rank: Regular Contributor
timestamp: March 28, 2025, 07:23:26 am
content: Ripple current rating is part of the datasheet, no? Otherwise, one of the main benefits of polarized capacitors (tant, nioboum, etc.) Is the size advantage. Irrelevant for most, there is also an advantage if you look into analytical reliability, ceramic capacitors drive parts count. While tantalums are less reliable than a single ceramic capacitor, they are not ten times worse.

author: VEGETA
author_rank: Super Contributor
timestamp: March 28, 2025, 10:47:05 am
content: Quotefor these polymers from panasonic yes, and it is very big like +7 amps @ 100khz. so if my device rated current is 3 amps and the inductor or switching part has higher ripple than that, it will be more than enough especially that it will be in parallel with smaller 0805 10u X5R ceramics.However, ceramics do not have such ripple figure but rather temperature raise vs current ripple.Quoteyou mean multiple ceramics in parallel are more reliable since current is divided? also, as you mentioned, the are multiples which means more parts and probably more cost. space can be an issue too but not for all cases.Quotei didn't understand.if you mean dc bias then yes, ceramics must be taken care of in this regard by compensating for this. the switchers i used specified a certain range of capacitance like 40-100uF total output capacitance which means i needed to calculate the ceramic derating at each rail and account for it. i got one 22u os-con polymer and 4.7u 3 ohm high esr elec. cap for damping... the rest are 10 0805 and 22u 1206 ceramics in parallel but still accounted for derating.the thing is, i see these modern polymers mentioned as MLCC alternatives which is why i asked if there is a performance advantage of replacing 5 ceramics with one of those. will total ripple figure be better for example?

author: mtwieg
author_rank: Frequent Contributor
timestamp: March 28, 2025, 11:21:59 am
content: Quote from: VEGETA on March 27, 2025, 10:55:04 pmIt's impossible to give a general answer to this... need some specific info about the application. Ripple current (both low and high frequency ripple), space constraints (both area and height), etc.

author: VEGETA
author_rank: Super Contributor
timestamp: March 28, 2025, 07:20:22 pm
content: Quotespace is not a big issue, the switcher is 1.2 mhz and the application shows some low freq ripple in full load, other similar application does not show low freq ripple but rather just the switching freq ripple itself.thus my question is more of a generic one.

author: KE5FX
author_rank: Super Contributor
timestamp: March 28, 2025, 07:37:24 pm
content: In low-volume production testing over the past couple of years, I've seen more bad ceramic caps than tantalums. A few of the former, but zero of the latter.Of course that says nothing about the long term, but anecdotally, in my own 4-year-old prototype, one ceramic has failed shorted and (again) no tantalums have failed.I do specify relatively expensive high-temp tantalums, but I don't call out anything special for the ceramics. I probably should start, but nowI'mthe prima ballerina who's making the factory change reels for "no good reason."Not hard to guess how that will play out in real life...

author: VEGETA
author_rank: Super Contributor
timestamp: March 28, 2025, 07:59:54 pm
content: Quote from: KE5FX on March 28, 2025, 07:37:24 pmso in your experience, the difference was in reliability not in performance. meaning, total output ripple and noise filteration was the same using both solutions?in my case i have 7-10 ceramics in parallel so that the total load is divided on them, which means one ceramic will operate at roughly 10% of its intended capability which in my own thinking will ensure no issue happens. + there is an OS-CON cap in parallel too.but when i saw these fancy small polymers, POS-CAP and SP-CAP, i thought I should ask fellow engineers on their own experience with them.

author: TimFox
author_rank: Super Contributor
timestamp: March 28, 2025, 08:20:26 pm
content: The electrolytic capacitors (aluminum and tantalum) differ from the ceramic capacitors (normally X7R or X5R Class II dielectrics) in their ESR, which affects filtration.A construction difference: the electrolyte that connects to the positive side of the polarized capacitors is, very roughly, a resistance in series with a relatively low-loss dielectric, so the ESR is not so strong a function of frequency.Polymer electrolytic capacitors show less of that parasitic series resistance than do traditional electrolytics.The ceramic capacitors have relatively low parasitic series resistance (in the metallization) and their ESR is dominated by the dielectric's inherent dissipation factor (D= 1/Q), which would give an ESR inversely proportional to frequency, a roughly constant fraction of the capacitive reactance magnitude 1/(wC).For decent capacitors, the ESR orDshould be well-presented in the manufacturer's data sheet.

author: KE5FX
author_rank: Super Contributor
timestamp: March 28, 2025, 08:38:48 pm
content: Quote from: VEGETA on March 28, 2025, 07:59:54 pmCouldn't say, really. In this application everything downstream has its own low-noise point-of-load regulation, so it really doesn't matter what comes out of the buck converter. Reliability is paramount. So at the moment at least, I'm not inclined to replace one or two polarized electrolytics with multiple MLCCs in future designs.

author: mtwieg
author_rank: Frequent Contributor
timestamp: March 28, 2025, 09:51:21 pm
content: Quote from: VEGETA on March 28, 2025, 07:20:22 pmIf switching frequency is that high then it's probably fine to use only MLCCs to decouple the output. Assuming the DCDC controller has decent control bandwidth, low frequency load transients will pass transparently to the input. As long as the source for the DCDC can source those transients, there's no need to add large bulk decoupling caps anywhere.Of course if the DCDC chip calls for a specific capacitor type I would follow that though.

author: VEGETA
author_rank: Super Contributor
timestamp: March 28, 2025, 10:19:37 pm
content: Quoteswitcher is TI DCAP3 which is tailored to use low esr ceramics.one of the applications has low freq transients which show ripple up to 25 mv p-p which is already fantastic, but other application does not even reach 5mv p-p. both on full load.i wanted to understand if larger value cap can help doing low freq filtering more than multiple small ones in parallel even if the later had less resistance.this is not considered a problem to my application at all but i just like to keep understanding and enhancing stuff.i do have large aishi polymer caps (2x 220uF low esr 20mohm) at the input in parallel with ceramics, but seems either i need bulkier ones to filter that low freq stuff or i need something else./??so this can be an input capacitor problem, can it? if this is the case then these new polymer caps are suitable since they have huge capacitance and very low esr and small size. esr of 50-90 mohm is not so small thus os-con ones seem more reasonable but these are significantly more expensive than other brands like aishi or apaq or lelon.my way was to put good quality polymers on input as bulk caps in parallel with 2-3 ceramics, while putting the excellent panasonic cap at the output.if someone has experience in the effect of input capacitor of buck regulators, he may inform us.thanks!

author: Vovk_Z
author_rank: Super Contributor
timestamp: March 30, 2025, 06:03:20 pm
content: All solid polymer caps are usually very fine for dc-dc and large ceramics too (except it can breck). The only possible 'No' for large solid caps can be high frequency, like 1 MHz and more because of natural self-resonance frequency (which can't be too high with large capacitance).I don't see a reason for tantalum caps in casual(usual) DC-DC unless there are reasons to use it - like you need good temperature stability (ultra wide working temperature range).

author: VEGETA
author_rank: Super Contributor
timestamp: April 11, 2025, 01:14:13 pm
content: I've been searching recently and found this SP-CAP:https://industrial.panasonic.com/ww/products/pt/sp-cap/models/EEFLR0J680Rit is 68u with very low ESR of 6mOhm, and very very low ESL even compared to theOS-CONI used previously which has 35mOhm ESR and noticeably bigger ESL due to the package. this made the SP-CAP has 3 times current capability.so will this further enhances ripple and noise performance? right now I am getting around 20-30mV p-p ripple and no noise output at 3.3v 2.5-3 amps output. the output shows 50-60hz ripple due to the device (game console,dreamcast) sips power at these frequencies but it was a really nice performance being 20-30mv total figure including the low freq. ripple. but you know sometimes we like to perfect the perfection for absolutely 0 reasonI love to experiment and learn, and I have other PSU products to make... so it is going to be worth it.right now i am using the OS-CON caps with multiple ceramics in parallel (5-10 ceramics, mostly 10u 0805 and some 22u 1206). another PSU product i made for another console uses only one OS-CON mentioned above and resulted in 3-5 mv p-p total ripple figure and no noise no low freq ripple but this is 5v at 2 amps (saturn).

author: temperance
author_rank: Super Contributor
timestamp: April 12, 2025, 01:50:20 pm
content: I didn't see it being mentioned. Replacing low ESR poly caps with MLCC capcitors will cause nasty resonances because of the very high Q of those capacitors.

author: VEGETA
author_rank: Super Contributor
timestamp: April 12, 2025, 03:41:14 pm
content: Quote from: temperance on April 12, 2025, 01:50:20 pmI am talking about the opposite which is using low ESR poly caps along with ceramics in parallel instead of full ceramics. I mentioned a 68u PS-CAP in last post to be used instead of an OS-CON poly.

author: TimFox
author_rank: Super Contributor
timestamp: April 12, 2025, 04:12:12 pm
content: The term "poly" here is confusing: you mean it for electrolytic (aluminum or tantalum) capacitors, but it is often used for film (polypropylene, polyester, etc.) capacitors.

author: VEGETA
author_rank: Super Contributor
timestamp: April 15, 2025, 11:20:10 am
content: Quote from: TimFox on April 12, 2025, 04:12:12 pmthe one Ilinkedabove is described as: Conductive Polymer Aluminum Electrolytic Capacitors.the SP-CAP brand is "conductive polymer aluminum elec. caps" which are layered.while POS-CAP brand is described as "conductive polymer tantalum solid capacitor"OS-CON is just regular aluminum solid polymer caps.^ all of those without liquid, since there is a hybrid brand with liquid but this is not what i want.i used an OS-CON before along with multiple ceramics. it was 22u with 35m esr. i wonder if replacing it with the above cap (and reduce the ceramics a bit to compensate for 68-22 capacitance) which has 6m esr and significantly higher ripple rating can actually make ripple filtering better, both for low and high freq.its price does not seem to be very costly as well.

author: mtwieg
author_rank: Frequent Contributor
timestamp: April 15, 2025, 01:31:51 pm
content: Quote from: VEGETA on March 28, 2025, 10:19:37 pmIf you're using a special controller type like this then conventional guidelines for buck converters may not apply. I don't think I've ever used a DCAP controller, but it seems like they are intended to work exclusively with MLCCs. Using them with low ESR polymer/tantalum caps might be possible, but you'd have to verify it yourself.Maybe you can try simulating your controller in TI's software (TI TINA, pspice, or simplis).

author: VEGETA
author_rank: Super Contributor
timestamp: April 15, 2025, 02:41:07 pm
content: Quote from: mtwieg on April 15, 2025, 01:31:51 pmit works with polymers for sure, I made boards with it and they function perfectly fine. all polymers used and not used won't be lower esr than ceramics, so this is fine. TI support also didn't object on this but the specifics of that type of converters is that there is a limited range of output capacitance and inductance that must be met.... it is met perfectly fine in my case.so if i replace the os-con cap with sp-cap + remove couple of other ceramics to compensate for output capacitance limit, that will be exactly the same for the buck regulator.one could go with that sp-cap which is 68u 6mohm esr + small ceramics like 10u 0805 which makes ESL very low compared to the previous solution. the os-con has x2-x5 more ESL and 35mohm esr + 22u 1206 x5r ceramics + 10u 0805 x5r ceramics... if 1206 ones replaced with just 0805 that would be better esr and esl.or as i think so.

author: VEGETA
author_rank: Super Contributor
timestamp: April 25, 2025, 02:14:14 pm
content: I was checking the data on these caps:https://industrial.panasonic.com/ww/products/pt/sp-cap/models/EEFLR0J680Rhttps://industrial.panasonic.com/ww/products/pt/os-con/models/35SVPF22Mand found the Capacitance vs Frequency graph... looks like after around 0.1 MHz it changes drastically in value, meaning capacitance becomes a lot bigger.so my switching regulator operates at 1.2 MHz, how can this figure affect it?

author: TimFox
author_rank: Super Contributor
timestamp: April 25, 2025, 02:20:29 pm
content: That’s the self-resonance, due to the parasitic series inductance.The impedance reaches its minimum at that frequency: above that, the reactance is inductive and rises with frequency.In a magnitude plot, the inductive stuff appears to be a decreasing capacitance with frequency.

author: VEGETA
author_rank: Super Contributor
timestamp: April 25, 2025, 03:54:12 pm
content: Quote from: TimFox on April 25, 2025, 02:20:29 pmBut it shows that it's capacitance increases with increased frequency after the resonance. For my application of 1.2 mhz switching what is the expected effect.?These parts have very low esl... I believe this is fantastic for transient response and ripple right?

author: TimFox
author_rank: Super Contributor
timestamp: April 25, 2025, 04:21:30 pm
content: Quote from: VEGETA on April 25, 2025, 03:54:12 pmThe graph of capacitance vs. frequency for the 35SVPF22M goes up to only the self-resonant frequency (approx. 1 MHz), where the series reactance becomes very low and the net impedance is only the ESR.Similarly, the graph of inductance starts at roughly the self-resonant frequency.With a very low reactance, the equivalent capacitance is very large.Note how the impedance increases at frequencies above self-resonance.(The graph for capacitance has a different x-axis, cutting off above 1 MHz, while the others go higher.)

author: mtwieg
author_rank: Frequent Contributor
timestamp: April 25, 2025, 05:19:31 pm
content: Quote from: VEGETA on April 25, 2025, 03:54:12 pmIn theory yes, having the capacitor SRF near the switching frequency will reduce the ripple voltage.Though in practice other parasitics will always throw this simple model off.Also a 1MHz SRF for such a capacitor is implausible, that implies an ESL of just 0.37nH. Even a 68uF MLCC in a smaller package has lower SRF. I'm guessing they are subtracting some of the inductance of the terminations or something....

author: VEGETA
author_rank: Super Contributor
timestamp: April 25, 2025, 05:34:15 pm
content: I use the 22u with multiple ceramics in parallel. Getting 25 mv pp at full load . Just want to see if I could eliminate more for perfection.So the capacitance will not actually increase with frequency after 1 mhz? It will stay 22u for all these values?These are panasonic parts and dayasheet should be accurate . Also there is a 3 terminal part to this one which promises 50 percent less esl.

author: TimFox
author_rank: Super Contributor
timestamp: April 25, 2025, 05:55:49 pm
content: Quote from: VEGETA on April 25, 2025, 05:34:15 pmPlease don't say "mhz" when you mean "MHz".For the physical component, at low frequencies the reactance of the part is approximately that of a constant capacitance.At much higher frequencies, the reactance of the part is approximately that of a constant inductance.At self-resonance, the capacitive reactance in series with the inductive reactance cancels, leaving only an ESR.The impedance of the physical part is the physical observable, comprising a "real" component (resistance) in series with an "imaginary" component (reactance). Both vary with frequency.

author: mtwieg
author_rank: Frequent Contributor
timestamp: April 25, 2025, 06:52:16 pm
content: Quote from: VEGETA on April 25, 2025, 05:34:15 pmAt the SRF, the "capacitance" effectively becomes infinite (i.e. the reactance of the part becomes zero). So not, it cannot continue to go up. Above the SRF it will look like an inductance (or a large negative capacitance, if you want to look at it that way).QuoteAh I didn't notice the three terminal aspect. If the terminals were arranged like an X2Y cap, then the low ESL might be plausible. But simply adding an extra terminal on one side shouldn't make a huge difference.

author: VEGETA
author_rank: Super Contributor
timestamp: April 25, 2025, 08:48:55 pm
content: along with that 22u panasonic i got multiple of these in parallel:https://product.samsungsem.com/mlcc/CL21A106KOQNNN.dohttps://product.samsungsem.com/mlcc/CL31A226KAHNNN.doas well as one 100n 0402 + a 4.7u elec. cap with 3 ohms esr (to act as a damper, didn''t check if it is actually needed and wasn''t recommended by the switcher ic)rails are 3.3v and 5v, total capacitance is <100u (including derating)Quotewhat i am trying to understand is the effect i should expect for my 1.2MHz switching frequency buck regulator output by using such a graphQuotethe one i linked is not the 3-terminal one though.but this one is low enough + combined with ceramics i believe i should have low esr esl total, correct?i have the exact circuit powering another device and the total ripple is < 5mv p-p at full load. however this one is 25 which is why i want to know if i can enhance it.once i return i will use the scope again and do some fft to help figure it out, mostly it is low frequency noise (50-120 hz and i have images showing 700-800 hz) since the device is 50 or 60 pal\ntsc console which i think sips power at those frequencies but this is my reasoning only