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| Are SuperCaps on 100-amp VCore supplies a thing yet? |
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| David Hess:
--- Quote from: frogblender on February 19, 2021, 08:15:15 pm ---Are SMT small supercaps with super-low ESR a thing yet? --- End quote --- Compared to ceramic or film capacitors? No, and offhand I do not know of any efforts in that direction. High frequency low ESR decoupling applications do not need more capacitance; they need lower impedance which is limited by ESR and ESL. Even higher performance applications build the decoupling capacitance into the board substrate between the power planes by adding a dielectric. |
| frogblender:
So the general consensus answer to my original question seems to be: No, small SMT supercaps with low ESR are not a thing yet. The lowest ESR listed on the "AVX BestCap" link (posted by @someone) is 30mΩ max, which is not bad... but it is in a giant 1"x2" package, so the lead inductance precludes its effectiveness as VCore decoupling... But mankind is getting there: 10 or 15 year ago supercaps didn't even exist (well, maybe they did, but I couldn't buy them on ebay). And the general trend on CPUs and such is: - lower core voltage (necessitating higher amperage, all else being equal) - higher wattage (necessitating higher amperage, all else being equal). So the trend is ridiculously higher and higher currents, which requires higher capacitance for a given ripple (and the trend is also smaller ripple specs too... 50mV ripple on a 80386's 3.3v supply is nothing. But 50mV on today's 700mV Vcore is a bluescreen). Anyhoo.... let's check back in 5 years.... |
| Someone:
--- Quote from: frogblender on February 23, 2021, 03:12:32 am ---So the trend is ridiculously higher and higher currents, which requires higher capacitance for a given ripple (and the trend is also smaller ripple specs --- End quote --- Or instead of more capacitance you can have smaller inductors, higher switching and crossover frequency, or more phases. Lots of ways to get low ripple/noise. --- Quote from: frogblender on February 23, 2021, 03:12:32 am ---The lowest ESR listed on the "AVX BestCap" link (posted by @someone) is 30mΩ max, which is not bad... but it is in a giant 1"x2" package, so the lead inductance precludes its effectiveness as VCore decoupling... --- End quote --- They included plots of impedance way up in frequency, it looks like the package inductance is well controlled and would be interesting to see what it looks like when coupled to a plane. But the volume is 10mm3/mF, compared to Ceramics around 50mm3/mF or Aluminium Polymer around 500mm3/mF. So if you want smaller volumes, yes they are able to do that. No height restrictions? Aluminium Polymer do ok per unit of surface area. |
| Siwastaja:
--- Quote from: frogblender on February 23, 2021, 03:12:32 am ---So the general consensus answer to my original question seems to be: No, small SMT supercaps with low ESR are not a thing yet. --- End quote --- "Yet", why would they need to be? They are already super-low ESR compared to the batteries they compete against. All improvements are being made to make them higher capacity so they could rival batteries, and this will be done at the cost of ESR. By no means can you expect 100x improvement in ESR, none of the buyers of these caps want it or need it. --- Quote ---The lowest ESR listed on the "AVX BestCap" link (posted by @someone) is 30mΩ max, which is not bad... but it is in a giant 1"x2" package, so the lead inductance precludes its effectiveness as VCore decoupling... --- End quote --- This is some two orders of magnitude worse than MLCC. Equally sized MLCC bank is maybe like 0.03 mOhm. Or you get 30mOhm from a tiny 0402 MLCC. --- Quote ---But mankind is getting there: --- End quote --- What makes you think anyone else than you wants to force a supercap in a use case where existing solution works way way better? All the supercap development is happening based on completely different applications, namely energy storage within seconds, not microseconds, typical marketing example would be a regenerative braking of a commuter train. Heck, the whole technology has been developed for such purposes. --- Quote ---- lower core voltage (necessitating higher amperage, all else being equal) - higher wattage (necessitating higher amperage, all else being equal). --- End quote --- Which is exactly why MLCC works there so well. Why would improving a technology 100x worse make any sense? I think you want to take a look at solid-state electrolytics as well. This really sounds like you have had some misunderstanding somewhere and now have this strange fixation. |
| Siwastaja:
To put it in numbers: In Vcore supply, you need, say, 1nH 1mOhm 10uF With MLCC, you get that, and just that, easily. With ultracaps, you could get 10nH 10mOhm 100000uF Or with tomorrow's even better ultracaps, you'd get: 10nH 10mOhm 200000uF They could of course offer some miniaturized ultracaps that would bring you 5nH 5mOhm 10000uF but I'm not sure anyone would buy them. The direction is towards larger and larger ultracap banks. |
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