Capacitance versus voltage for X7S caps?
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From: Joerg on 30 Mar 2010 12:04 Tim Williams wrote: > "Don Klipstein" <don(a)manx.misty.com> wrote in message > news:slrnhr2u17.idg.don(a)manx.misty.com... >> "Electrolytic" makes an alarm bell go off in my head against >> expectation of capacitance refusing to vary with voltage. >> >> Is there a reason for polymer to fix this for aluminum electrolytics? > > Tantalums are quite excellent (typically 10%, stable enough e.g. for long > period timing), but they have a tendancy to explode. > > By removing the moist electrolyte from the capacitor, replacing it with a > conductive organic polymer, the alpos get tantalum grade performance without > the risk of incineration. > Do you know how they take hardcore freezes, like north of the Klondike in January? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: legg on 30 Mar 2010 17:30 On Tue, 30 Mar 2010 09:04:08 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Tim Williams wrote: >> "Don Klipstein" <don(a)manx.misty.com> wrote in message >> news:slrnhr2u17.idg.don(a)manx.misty.com... >>> "Electrolytic" makes an alarm bell go off in my head against >>> expectation of capacitance refusing to vary with voltage. >>> >>> Is there a reason for polymer to fix this for aluminum electrolytics? >> >> Tantalums are quite excellent (typically 10%, stable enough e.g. for long >> period timing), but they have a tendancy to explode. >> >> By removing the moist electrolyte from the capacitor, replacing it with a >> conductive organic polymer, the alpos get tantalum grade performance without >> the risk of incineration. >> > >Do you know how they take hardcore freezes, like north of the Klondike >in January? Oscon aluminum organic polymer are characterized to -55degC., with less than 10% cap reduction. At 4.7uF, ESR is in the 80mR range. Later developers tend to follow this. RL
From: Joerg on 30 Mar 2010 17:07 legg wrote: > On Tue, 30 Mar 2010 09:04:08 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Tim Williams wrote: >>> "Don Klipstein" <don(a)manx.misty.com> wrote in message >>> news:slrnhr2u17.idg.don(a)manx.misty.com... >>>> "Electrolytic" makes an alarm bell go off in my head against >>>> expectation of capacitance refusing to vary with voltage. >>>> >>>> Is there a reason for polymer to fix this for aluminum electrolytics? >>> Tantalums are quite excellent (typically 10%, stable enough e.g. for long >>> period timing), but they have a tendancy to explode. >>> >>> By removing the moist electrolyte from the capacitor, replacing it with a >>> conductive organic polymer, the alpos get tantalum grade performance without >>> the risk of incineration. >>> >> Do you know how they take hardcore freezes, like north of the Klondike >> in January? > > Oscon aluminum organic polymer are characterized to -55degC., with > less than 10% cap reduction. At 4.7uF, ESR is in the 80mR range. > > Later developers tend to follow this. > I have used Oscons on another project. They are very expensive and in this case I need 100V and the height cannot be more than 2.5mm or around 0.100". -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: legg on 31 Mar 2010 07:42 On Tue, 30 Mar 2010 14:07:58 -0700, Joerg <invalid(a)invalid.invalid> wrote: >legg wrote: <snip> >>> Do you know how they take hardcore freezes, like north of the Klondike >>> in January? >> >> Oscon aluminum organic polymer are characterized to -55degC., with >> less than 10% cap reduction. At 4.7uF, ESR is in the 80mR range. >> >> Later developers tend to follow this. >> > >I have used Oscons on another project. They are very expensive and in >this case I need 100V and the height cannot be more than 2.5mm or around >0.100". I'm not sure if you've actually stated your requirement at some time or another. You seem to be merely floating generalized but limited questions regarding part characteristics. What is the actual requirement? RL
From: Joerg on 31 Mar 2010 14:12
legg wrote: > On Tue, 30 Mar 2010 14:07:58 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> legg wrote: > <snip> >>>> Do you know how they take hardcore freezes, like north of the Klondike >>>> in January? >>> Oscon aluminum organic polymer are characterized to -55degC., with >>> less than 10% cap reduction. At 4.7uF, ESR is in the 80mR range. >>> >>> Later developers tend to follow this. >>> >> I have used Oscons on another project. They are very expensive and in >> this case I need 100V and the height cannot be more than 2.5mm or around >> 0.100". > > I'm not sure if you've actually stated your requirement at some time > or another. You seem to be merely floating generalized but limited > questions regarding part characteristics. > No, I have in a follow-up post in this thread, that the graph ends at 50V but I need to know higher. Oscons don't get into that range much. > What is the actual requirement? > I need to replace an electrolytic that was used so far because it's too large and also prone to failure. Total 100uF/100V, although in a pinch we could scrape by with a 63V rating if we zener any larger excursions than 55V or so. High pulsed load, easily two amps. Hi-rel application meaning stress fracture is an issue with very large SMT footprints. I don't want to get up to 2220, better stay with 1812. Height restriction 2.5mm or just under 0.100". Nominal voltage is 50V but we have to (ideally) allow excursions up to 70V because this is the only capacitance at the end of a cable that can easily be 250ft long in some situations. If X7S really drops by around 50% as I have a hunch it will then we'll have to see if the remaing 50uF is going to be enough. X7R in 2220 would be better but we can't really fit that many, plus the stress fracture issue. So, the classic situation of being between a rock and a hard spot. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |