On Friday, November 16, 2018 at 10:05:23 AM UTC-5, 69883925...@nospam.org wrote:> George Herold wrote > >Hey, I assume COG/NPO caps don't have any voltage coef. (I use those > >for AC coupling, signal filters.) > > Assuming is a dangerous thing... but poly based caps should be OK, > use those in my LC meter. > I will measure some of those ceramic caps when I get around to it.Right... I saw data sheets somewhere that looked OK. Hey I'll try JL's circuit and measure some. It's Friday, I'm allowed to do something fun. George H.
X5R vs X7R MLCC
Started by ●November 14, 2018
Reply by ●November 16, 20182018-11-16
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 09:29:42 GMT, <698839253X6D445TD@nospam.org> wrote:>John Larkin wrote >>On Thu, 15 Nov 2018 17:14:02 GMT, <698839253X6D445TD@nospam.org> >>wrote: >> >>>John Larkin wrote >>>>https://www.dropbox.com/s/ilppasx0ym7b98y/Ccap_CV.JPG?dl=0 >>> >>>Terrible. >>>Better use tantalum? >>>What am I missing here? >> >>There's nothing missing here. I just measured a cap. >> >>That 4.7u is fine to filter the output of a 1.2 or 3.3 volt switcher, >>or for AC coupling. Or use the 47u 6.3v version, which has an even >>worse cv curve. >> >>Tantalums have a lot of ESR, which is sometimes good, sometimes bad. >>They are always big and expensive. > >Yes, OK tantalums are more expensive, >I use those all the time for linear regulator decoupling.Derate 3:1 on voltage, or they may detonate. With mandatory 3:1 derating, they are worse than a ceramic! I posted a trick for using ceramics on the output of LM317s.>Again, do not save on parts... >I could not see me use a capacitor for AC coupling between stages if its value >could be 10x out of specified range. > >Makes me wonder too how microphonic those caps are? >With microphonic I mean creating voltages when vibrating? > >I sort of like to tap on boards with a pen... to find dry joints etc.. >Was no there a tread about it here years ago? >And the reverse, making sound when AC is applied. > >But then I am biased, I like tantalums, never had a problem with those.. >except when put in the wrong way around...They are erratic. Some types work fine, and another batch of the same parts explode. https://www.dropbox.com/s/pa3lmrfw0ejzt5p/Bang.jpg?dl=0 https://www.dropbox.com/s/xtqm92we4et98tw/Fried_Tant_1.JPG?dl=0 -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●November 16, 20182018-11-16
John Larkin wrote>They are erratic. Some types work fine, and another batch of the same >parts explode. > >https://www.dropbox.com/s/pa3lmrfw0ejzt5p/Bang.jpg?dl=0 > >https://www.dropbox.com/s/xtqm92we4et98tw/Fried_Tant_1.JPG?dl=0I bought an assortment of values of caps like in the bottom link some years ago on ebay, only a few left now, not one problem, much of that stuff is on 24/7. Sure 35 V with 12V input or 5 V on it, always have some margin. But also in industry, all I remember is 1 case where a tantalum exploded, took some cards in 19 inch rack with it. Was nothing much left of it, so we do not know if it was in the wrong way. Much better than those electrolytics, and much better ESR in the long run I think. When using electrolytics I often put 100 nF or something in parallel, in case of tantalums not.
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 06:37:24 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Friday, November 16, 2018 at 4:30:28 AM UTC-5, 69883925...@nospam.org wrote: >> John Larkin wrote >> >On Thu, 15 Nov 2018 17:14:02 GMT, <698839253X6D445TD@nospam.org> >> >wrote: >> > >> >>John Larkin wrote >> >>>https://www.dropbox.com/s/ilppasx0ym7b98y/Ccap_CV.JPG?dl=0 >> >> >> >>Terrible. >> >>Better use tantalum? >> >>What am I missing here? >> > >> >There's nothing missing here. I just measured a cap. >> > >> >That 4.7u is fine to filter the output of a 1.2 or 3.3 volt switcher, >> >or for AC coupling. Or use the 47u 6.3v version, which has an even >> >worse cv curve. >> > >> >Tantalums have a lot of ESR, which is sometimes good, sometimes bad. >> >They are always big and expensive. >> >> Yes, OK tantalums are more expensive, >> I use those all the time for linear regulator decoupling. >> Again, do not save on parts... >> I could not see me use a capacitor for AC coupling between stages if its value >> could be 10x out of specified range. >Hey, I assume COG/NPO caps don't have any voltage coef. (I use those >for AC coupling, signal filters.) >> >> Makes me wonder too how microphonic those caps are? >> With microphonic I mean creating voltages when vibrating? >> >> I sort of like to tap on boards with a pen... to find dry joints etc.. >> Was no there a tread about it here years ago? >> And the reverse, making sound when AC is applied. >> >> But then I am biased, I like tantalums, never had a problem with those.. >> except when put in the wrong way around... >You have to picky about manufacturers, someone saved a few cents on >cheaper tants, and the 35V ones failed at 15-20V... semi my mistake >as I used them on a 24V supply line. (older design... in the past I >don't think tant's were so flaky.) > >George H.MnO2 tantalums are ignited by high current, namely dV/dT, so are poor choices to put on supply rails, unless severely derated on voltage. Polymer aluminums and polymer tantalums are OK. Polymer aluminums are great, but ESR is too low for some regulators. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 07:49:44 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Friday, November 16, 2018 at 10:05:23 AM UTC-5, 69883925...@nospam.org wrote: >> George Herold wrote >> >Hey, I assume COG/NPO caps don't have any voltage coef. (I use those >> >for AC coupling, signal filters.) >> >> Assuming is a dangerous thing... but poly based caps should be OK, >> use those in my LC meter. >> I will measure some of those ceramic caps when I get around to it. > >Right... I saw data sheets somewhere that looked OK. Hey I'll try >JL's circuit and measure some.C0Gs have low voltage coefficients but don't come in big values. Just lately people are making big ones, like 0.5 uF, but I don't know about those. Kemet claims "No capacitance change with respect to applied rated DC voltage." Just hope your C-meter has no voltage coefficient! Maybe add Phil's second resistor.> >It's Friday, I'm allowed to do something fun.Why wait til Friday? -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●November 16, 20182018-11-16
On 11/16/18 10:57 AM, John Larkin wrote:> On Fri, 16 Nov 2018 09:29:42 GMT, <698839253X6D445TD@nospam.org> > wrote: > >> John Larkin wrote >>> On Thu, 15 Nov 2018 17:14:02 GMT, <698839253X6D445TD@nospam.org> >>> wrote: >>> >>>> John Larkin wrote >>>>> https://www.dropbox.com/s/ilppasx0ym7b98y/Ccap_CV.JPG?dl=0 >>>> >>>> Terrible. >>>> Better use tantalum? >>>> What am I missing here? >>> >>> There's nothing missing here. I just measured a cap. >>> >>> That 4.7u is fine to filter the output of a 1.2 or 3.3 volt switcher, >>> or for AC coupling. Or use the 47u 6.3v version, which has an even >>> worse cv curve. >>> >>> Tantalums have a lot of ESR, which is sometimes good, sometimes bad. >>> They are always big and expensive. >> >> Yes, OK tantalums are more expensive, >> I use those all the time for linear regulator decoupling. > > Derate 3:1 on voltage, or they may detonate. With mandatory 3:1 > derating, they are worse than a ceramic! > > I posted a trick for using ceramics on the output of LM317s. > > >> Again, do not save on parts... >> I could not see me use a capacitor for AC coupling between stages if its value >> could be 10x out of specified range. >> >> Makes me wonder too how microphonic those caps are? >> With microphonic I mean creating voltages when vibrating? >> >> I sort of like to tap on boards with a pen... to find dry joints etc.. >> Was no there a tread about it here years ago? >> And the reverse, making sound when AC is applied. >> >> But then I am biased, I like tantalums, never had a problem with those.. >> except when put in the wrong way around... > > They are erratic. Some types work fine, and another batch of the same > parts explode. > > https://www.dropbox.com/s/pa3lmrfw0ejzt5p/Bang.jpg?dl=0 > > https://www.dropbox.com/s/xtqm92we4et98tw/Fried_Tant_1.JPG?dl=0 > >They're sensitive to thermal history, for one thing. I've had good luck with them on the output side of 78xx-type regulators, but I sure don't use them on the input side. <https://electrooptical.net/www/sed/TantalumCapReforming_25272-what_a_cap_astrophe.pdf> Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●November 16, 20182018-11-16
On 11/16/18 11:37 AM, John Larkin wrote:> On Fri, 16 Nov 2018 06:37:24 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > >> On Friday, November 16, 2018 at 4:30:28 AM UTC-5, 69883925...@nospam.org wrote: >>> John Larkin wrote >>>> On Thu, 15 Nov 2018 17:14:02 GMT, <698839253X6D445TD@nospam.org> >>>> wrote: >>>> >>>>> John Larkin wrote >>>>>> https://www.dropbox.com/s/ilppasx0ym7b98y/Ccap_CV.JPG?dl=0 >>>>> >>>>> Terrible. >>>>> Better use tantalum? >>>>> What am I missing here? >>>> >>>> There's nothing missing here. I just measured a cap. >>>> >>>> That 4.7u is fine to filter the output of a 1.2 or 3.3 volt switcher, >>>> or for AC coupling. Or use the 47u 6.3v version, which has an even >>>> worse cv curve. >>>> >>>> Tantalums have a lot of ESR, which is sometimes good, sometimes bad. >>>> They are always big and expensive. >>> >>> Yes, OK tantalums are more expensive, >>> I use those all the time for linear regulator decoupling. >>> Again, do not save on parts... >>> I could not see me use a capacitor for AC coupling between stages if its value >>> could be 10x out of specified range. >> Hey, I assume COG/NPO caps don't have any voltage coef. (I use those >> for AC coupling, signal filters.) >>> >>> Makes me wonder too how microphonic those caps are? >>> With microphonic I mean creating voltages when vibrating? >>> >>> I sort of like to tap on boards with a pen... to find dry joints etc.. >>> Was no there a tread about it here years ago? >>> And the reverse, making sound when AC is applied. >>> >>> But then I am biased, I like tantalums, never had a problem with those.. >>> except when put in the wrong way around... >> You have to picky about manufacturers, someone saved a few cents on >> cheaper tants, and the 35V ones failed at 15-20V... semi my mistake >> as I used them on a 24V supply line. (older design... in the past I >> don't think tant's were so flaky.) >> >> George H. > > MnO2 tantalums are ignited by high current, namely dV/dT, so are poor > choices to put on supply rails, unless severely derated on voltage. > > Polymer aluminums and polymer tantalums are OK. Polymer aluminums are > great, but ESR is too low for some regulators.A polymer aluminum and a pulse-rated sub-ohm resistor make a good combination for that. I usually start with a zero-ohm jumper. Putting a lead capacitor on the feedback network of a 317-style regulator helps with that too, at the price of somewhat degraded noise. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●November 16, 20182018-11-16
On Thursday, November 15, 2018 at 12:32:46 PM UTC-7, Phil Hobbs wrote:> On 11/15/18 1:53 PM, gnuarm.deletethisbit@gmail.com wrote: > > On Thursday, November 15, 2018 at 11:12:09 AM UTC-5, Phil Hobbs wrote: > >> On 11/15/18 10:59 AM, DemonicTubes wrote: > >>> On Wednesday, November 14, 2018 at 7:15:54 PM UTC-7, Phil Hobbs wrote: > >>>> On 11/14/18 6:49 PM, gnuarm.deletethisbit@gmail.com wrote: > >>>>> I use a 1210 X5R 25V 10% MLCC for input DC blocking. Supply is > >>>>> drying up and I want to place an order to support production for a > >>>>> while. In performing a Digikey/Mouser search I see there are now X7R > >>>>> devices in the same footprint. I know the X7R will be more stable > >>>>> under DC voltage which is an advantage *if* there is much DC on the > >>>>> input. The amplifier circuit has a 6 volt DC bias on the input (half > >>>>> way to the +12 volt rail). The caps prevent the input from seeing > >>>>> this bias. The design passes all functional tests in production > >>>>> (including frequency response) with the X5R devices. > >>>>> > >>>>> I'm thinking of making the X7R an alternate device going forward. > >>>>> There are only four devices on the board, so a small increase in > >>>>> price is not so significant. I'm just wondering if there is any > >>>>> technical downside to using the X7R formulation in place of the X5R. > >>>>> Or is the X7R formulation all upside relative to the X5R? > >>>> > >>>> Apples to apples, X7R is better, for sure. However, high-density MLCCs > >>>> are all over the map in performance depending on both manufacturer and > >>>> part number. You really have to find the characteristic curves to know. > >>>> > >>>> We've all been feeling the MLCC shortage this year, so I put up a blog > >>>> post with links to a bunch of makers' characteristic curves. > >>>> > >>>> <https://www.electrooptical.net/News/high-value-ceramic-capacitors-they-stink-and-you-cant-get-them-anyway> > >>>> > >>>> Samsung has decent characteristic curves published on Digikey. (Note > >>>> that it's the characteristics link and not the datasheet link that you > >>>> want. Cute eh?) > >>>> > >>>> Cheers > >>>> > >>>> Phil Hobbs > >>>> > >>>> -- > >>>> Dr Philip C D Hobbs > >>>> Principal Consultant > >>>> ElectroOptical Innovations LLC / Hobbs ElectroOptics > >>>> Optics, Electro-optics, Photonics, Analog Electronics > >>>> Briarcliff Manor NY 10510 > >>>> > >>>> http://electrooptical.net > >>>> http://hobbs-eo.com > >>> > >>> I was just informed 2 days ago that my Digi-Key order of Samsung caps is on back order :-( > >>> > >>> Going to run a production batch with untested no-namers...wish me luck! > >>> > >> > >> I'd test them first. It's not that hard--put two in series and bias the > >> middle. > > > > Checking for what, even voltage? Then check with a capacitance meter??? > > > > Rick C. > > > > Tesla referral code +-+-+ https://ts.la/richard11209 > > > > No, you put a large resistor across the ends so there's no DC on the > meter, ground one end, bias the middle via another large resistor, and > put a C meter across the ends. No muss, no fuss. > > Cheers > > Phil Hobbs > > -- > Dr Philip C D Hobbs > Principal Consultant > ElectroOptical Innovations LLC / Hobbs ElectroOptics > Optics, Electro-optics, Photonics, Analog Electronics > Briarcliff Manor NY 10510 > > http://electrooptical.net > http://hobbs-eo.comWhile waiting for the new ones I decided to use this method to test some of my current stock of Samsung parts. These are ceramic 470nF 50V X7R in an 0805 package. Samsung P/N: CL21B474KBFNFNE Source: Digi-Key I tested these from 0-30V (I normally expose these to 15-24V in use). Here are my results: https://imgur.com/JKFGJD9 Impressed they start a bit higher than rated, but the capacitance drops off faster than expected. Here is what their datasheet shows: https://imgur.com/a/8uEMHc0 Hmm, something isn't right. I should be on that upper red curve (X7R 50V). They show a 10% decline in capacitance by 30V, while I am measuring over 50%! Very good chance I'm doing something stupid. This is my test setup: https://imgur.com/a/x92g3iW I suppose it is possible the resistor on the right is affecting the readings from my LCR. Maybe I'm missing something else silly...
Reply by ●November 16, 20182018-11-16
On Friday, November 16, 2018 at 10:59:12 AM UTC-6, Phil Hobbs wrote:> On 11/16/18 10:57 AM, John Larkin wrote: > > On Fri, 16 Nov 2018 09:29:42 GMT, <698839253X6D445TD@nospam.org> > > wrote: > > > >> John Larkin wrote > >>> On Thu, 15 Nov 2018 17:14:02 GMT, <698839253X6D445TD@nospam.org> > >>> wrote: > >>> > >>>> John Larkin wrote > >>>>> https://www.dropbox.com/s/ilppasx0ym7b98y/Ccap_CV.JPG?dl=0 > >>>> > >>>> Terrible. > >>>> Better use tantalum? > >>>> What am I missing here? > >>> > >>> There's nothing missing here. I just measured a cap. > >>> > >>> That 4.7u is fine to filter the output of a 1.2 or 3.3 volt switcher, > >>> or for AC coupling. Or use the 47u 6.3v version, which has an even > >>> worse cv curve. > >>> > >>> Tantalums have a lot of ESR, which is sometimes good, sometimes bad. > >>> They are always big and expensive. > >> > >> Yes, OK tantalums are more expensive, > >> I use those all the time for linear regulator decoupling. > > > > Derate 3:1 on voltage, or they may detonate. With mandatory 3:1 > > derating, they are worse than a ceramic! > > > > I posted a trick for using ceramics on the output of LM317s. > > > > > >> Again, do not save on parts... > >> I could not see me use a capacitor for AC coupling between stages if its value > >> could be 10x out of specified range. > >> > >> Makes me wonder too how microphonic those caps are? > >> With microphonic I mean creating voltages when vibrating? > >> > >> I sort of like to tap on boards with a pen... to find dry joints etc.. > >> Was no there a tread about it here years ago? > >> And the reverse, making sound when AC is applied. > >> > >> But then I am biased, I like tantalums, never had a problem with those.. > >> except when put in the wrong way around... > > > > They are erratic. Some types work fine, and another batch of the same > > parts explode. > > > > https://www.dropbox.com/s/pa3lmrfw0ejzt5p/Bang.jpg?dl=0 > > > > https://www.dropbox.com/s/xtqm92we4et98tw/Fried_Tant_1.JPG?dl=0 > > > > > > They're sensitive to thermal history, for one thing. I've had good luck > with them on the output side of 78xx-type regulators, but I sure don't > use them on the input side. > > <https://electrooptical.net/www/sed/TantalumCapReforming_25272-what_a_cap_astrophe.pdf>Interesting article. I don't have good statistics because I've never gotten manufacturing to focus on documenting things rather than just getting units fixed and shipped. What I've seen is that we have about two failures in 100 units on a 150 uF tantalum cap. The failure is not hard to find once you are aware to look for it. I'm wondering how slow "slow" is for the voltage ramp. "I had the idea to build a capacitor-postprocessing fixture. Its function was to slowly ramp up the voltage applied to the PCB with enough current capacity to power everything on the PCB but with sufficient internal resistance to limit transient capacitor-clearing fault current." I have jumpers around sub ohm current measurement resistors for the UUT. If The current sense resistor could be replaced with a current limiting resistor. We already have a step in the test procedure to turn on power while watching LEDs that indicate the power supplies are up. We could add a step of removing the zero ohm jumper, turn on power while watching the LEDs, then install the jumper and continue testing. With a current limit resistor would a normal power supply ramp up be ok to clear the short without damage? I believe the PSU devices can provide 1 Amp. I guess it doesn't really matter so much. If a large enough resistor to prevent damage is used and the short doesn't clear the voltage would be dragged down enough to flag the problem still. If it does clear we are ahead of the game. It doesn't take long to replace the failed caps. So the question is whether this would use more time than just finding and fixing the shorts when they blow. Rick C. Tesla referral code +--+ https://ts.la/richard11209
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 16:16:47 GMT, <698839253X6D445TD@nospam.org> wrote:>John Larkin wrote >>They are erratic. Some types work fine, and another batch of the same >>parts explode. >> >>https://www.dropbox.com/s/pa3lmrfw0ejzt5p/Bang.jpg?dl=0 >> >>https://www.dropbox.com/s/xtqm92we4et98tw/Fried_Tant_1.JPG?dl=0 > >I bought an assortment of values of caps like in the bottom link some years ago on ebay, >only a few left now, >not one problem, much of that stuff is on 24/7.Tants are fine steady-state. It the turn-on transition that ignites them.> >Sure 35 V with 12V input or 5 V on it, always have some margin. > >But also in industry, all I remember is 1 case where a tantalum exploded, >took some cards in 19 inch rack with it. >Was nothing much left of it, so we do not know if it was in the wrong way. > >Much better than those electrolytics, and much better ESR in the long run I think. >When using electrolytics I often put 100 nF or something in parallel, >in case of tantalums not.Usually my boards are well seeded with 1 uF bypass caps on power planes. -- John Larkin Highland Technology, Inc lunatic fringe electronics
