Capacitance versus voltage for X7S caps?
in [Design]
|
Prev: Automotive datalogger power(down) supply strategy
Next: What do you call it/where do you get it?
From: Spehro Pefhany on 25 Mar 2010 16:28 On Thu, 25 Mar 2010 13:17:58 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Fred Bartoli wrote: >> whit3rd a �crit : >>> On Mar 25, 9:48 am, Joerg <inva...(a)invalid.invalid> wrote: >>>> qrk wrote: >>>>> If you can't find data, send me a sample and I can run it on our >>>>> HP4194 impedance analyzer. >>>> Thanks for the offer, Mark. I have a HP4191 here so I could also ... >>>> It blows my mind that maufacturers do not furnish such data. >>> >>> I think there's an important point being missed here: capacitance is >>> a term in a linear equation, and the behavior of these capacitor >>> materials >>> is NONLINEAR. The 'capacitance' change is undefined unless you >>> specify a full test setup. >>> >>> The nonlinearity of these materials includes hysteresis and memory >>> effects and acoustic emission and sensitivity. They don't have >>> 'capacitance versus voltage', they have nonlinearity. The >>> manufacturer >>> has good reasons to only specify a few limits. >> >> Well, in fact that's even worse because some relaxation time factors in >> too. >> > >Those factors are all minor when using capacitors for bypassing. For all >traditional ceramics such as X7R, Z5U or Y5V (the latter two having much >higher non-linearity) the manufacturers give capacitance versus voltage >spec. For X7S they don't. Somehow that smells like a "Marketing didn't >like the graphs" situation. > >All I need to know is how much C will be left at 50% voltage, roughly. I >don't care whether it's non-linear. Did you see this? http://www.tecdia.com/us/product/hf/ultra_capacitor.html
From: Joerg on 25 Mar 2010 16:33 Spehro Pefhany wrote: > On Thu, 25 Mar 2010 13:17:58 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Fred Bartoli wrote: >>> whit3rd a �crit : >>>> On Mar 25, 9:48 am, Joerg <inva...(a)invalid.invalid> wrote: >>>>> qrk wrote: >>>>>> If you can't find data, send me a sample and I can run it on our >>>>>> HP4194 impedance analyzer. >>>>> Thanks for the offer, Mark. I have a HP4191 here so I could also ... >>>>> It blows my mind that maufacturers do not furnish such data. >>>> I think there's an important point being missed here: capacitance is >>>> a term in a linear equation, and the behavior of these capacitor >>>> materials >>>> is NONLINEAR. The 'capacitance' change is undefined unless you >>>> specify a full test setup. >>>> >>>> The nonlinearity of these materials includes hysteresis and memory >>>> effects and acoustic emission and sensitivity. They don't have >>>> 'capacitance versus voltage', they have nonlinearity. The >>>> manufacturer >>>> has good reasons to only specify a few limits. >>> Well, in fact that's even worse because some relaxation time factors in >>> too. >>> >> Those factors are all minor when using capacitors for bypassing. For all >> traditional ceramics such as X7R, Z5U or Y5V (the latter two having much >> higher non-linearity) the manufacturers give capacitance versus voltage >> spec. For X7S they don't. Somehow that smells like a "Marketing didn't >> like the graphs" situation. >> >> All I need to know is how much C will be left at 50% voltage, roughly. I >> don't care whether it's non-linear. > > Did you see this? > > http://www.tecdia.com/us/product/hf/ultra_capacitor.html > Shazam! Thanks, this stuff does look quite good. If this is true I wonder why on earth the others don't advertise it properly. But it's not really a surprise since many datasheets are seriously dumbed-down these days. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Spehro Pefhany on 25 Mar 2010 16:50 On Thu, 25 Mar 2010 09:48:27 -0700, Joerg <invalid(a)invalid.invalid> wrote: >qrk wrote: >> If you can't find data, send me a sample and I can run it on our >> HP4194 impedance analyzer. >> > >Thanks for the offer, Mark. I have a HP4191 here so I could also do >that. But this project is too fast-track. Needs to go into layout >ideally by tonight or tomorrow morning, no time to get samples here. > >It blows my mind that maufacturers do not furnish such data. This time >that could cost the sales since w may go hi-rel electrolytic, to be on >the safe side. Do you have access to the EIA-198-1-F, EN 132100/ IEC 60384-10 etc? Looks like voltage coefficent _limits_ are covered by the sub-class under EN 132100/ IEC 60384-10 at least, but I don't see the sub-class 2-letter code listed in the TDK datasheet.
From: Joerg on 25 Mar 2010 17:08 Spehro Pefhany wrote: > On Thu, 25 Mar 2010 09:48:27 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> qrk wrote: >>> If you can't find data, send me a sample and I can run it on our >>> HP4194 impedance analyzer. >>> >> Thanks for the offer, Mark. I have a HP4191 here so I could also do >> that. But this project is too fast-track. Needs to go into layout >> ideally by tonight or tomorrow morning, no time to get samples here. >> >> It blows my mind that maufacturers do not furnish such data. This time >> that could cost the sales since w may go hi-rel electrolytic, to be on >> the safe side. > > Do you have access to the EIA-198-1-F, EN 132100/ IEC 60384-10 etc? > > Looks like voltage coefficent _limits_ are covered by the sub-class > under EN 132100/ IEC 60384-10 at least, but I don't see the sub-class > 2-letter code listed in the TDK datasheet. > Unfortunately I don't have access to those. But standards are sort of iffy in the capacitor business. For example, I found two vastly different heights for the supposedly standardized 2220 SMT-package. One listed 2.2mm and would fit in our situation, the other listed 0.160" and would be way too tall. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Robert Baer on 26 Mar 2010 16:38
Joerg wrote: > qrk wrote: >> If you can't find data, send me a sample and I can run it on our >> HP4194 impedance analyzer. >> > > Thanks for the offer, Mark. I have a HP4191 here so I could also do > that. But this project is too fast-track. Needs to go into layout > ideally by tonight or tomorrow morning, no time to get samples here. > > It blows my mind that maufacturers do not furnish such data. This time > that could cost the sales since w may go hi-rel electrolytic, to be on > the safe side. > ....in which case that 0.1 height restriction gets blown. |