On Friday, 16 November 2018 15:57:26 UTC, 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=0Tantalums acquire microscopic defects due to soldering. These greatly reduce voltacity (or some similar word). Lack of any flexibility in the connections also causes this problem. To correct this, tants need a healing process after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage. NT
X5R vs X7R MLCC
Started by ●November 14, 2018
Reply by ●November 16, 20182018-11-16
Reply by ●November 16, 20182018-11-16
On 11/16/18 2:46 PM, John Larkin wrote:> On Fri, 16 Nov 2018 14:04:37 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 11/16/18 1:17 PM, John Larkin wrote: >>> On Fri, 16 Nov 2018 12:01:23 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> 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 >>> >>> A cap from ADJ to ground seems to make an LM317 regulator ceramic cap >>> tolerant. 10 nF is usually about right. I'd expect that to reduce HF >>> noise a little. >> >> Interesting. Lead caps help buck switchers deal with large output caps, >> but work the other way on 317s? >> >> Cheers >> >> Phil Hobbs > > https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?dl=0 > > https://www.dropbox.com/s/9q80heyfbwh5frp/317_comp.jpg?dl=0 > > 20 or 30 nF and no R6 works about as well. > > Lead caps work with switchers that have a fb pin that's ground > referenced. I tried a cap across the upper divider resistor of a 317, > and that makes ringing worse. The cap to ground was an empirical > (fiddled) discovery. It actually works. > > I need to verify this for LM1117; we use a lot of those. > > I sometimes use a 317 with FB grounded, to make 1.25V for an ARM core. > That doesn't work with my trick.No kidding? ;) 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 Friday, November 16, 2018 at 2:19:58 PM UTC-6, tabb...@gmail.com wrote:> On Friday, 16 November 2018 15:57:26 UTC, 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 > > Tantalums acquire microscopic defects due to soldering. These greatly reduce voltacity (or some similar word). Lack of any flexibility in the connections also causes this problem. To correct this, tants need a healing process after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage.How slow is slow? What size resistor? I was thinking of incorporating this into the test procedure for a board using a tant cap that fails on first test far more often than other components. On second thought, without having a way to properly analyze the problem, maybe it's better to let the cap fail and be replaced. Fixing one short on a part may be setting it up for a later failure in the field??? Rick C. Tesla referral code ++++ https://ts.la/richard11209
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 12:17:28 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Friday, November 16, 2018 at 12:22:40 PM UTC-5, DemonicTubes wrote: >> 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.com >> >> While 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... > >OK I first tried JL's method. And then Phil's. Phils's sorta worked >but the cheap meter would sometimes lose it's mind.I tend to not trust L or C meters, especially cheap ones. I connect a 50 ohm sine wave generator to a cap or inductor and spin the knob and watch the frequency response, which tells me a lot in a few seconds.>JL's worked fine... but I made a factor of two mistake in the math.. >(I forgot the phase effects.)If the voltage across the cap is small compared to the generator open-circuit voltage, you can pretend that the generator is shorted, calculate the current, and use the frequency and current to calculate C. Ignore phase. Or Spice it to be accurate!> >I saw no change (V = 0-60V) in the 0.01uF cog, nor in a 0.1 uF cog. >A 0.01 uF X7R only changed by ~10%. 0.1uF X7R decreased to about 35% >of it's 0 V value at 60V. A 1 uF x7r was down to 20% at 60V. >These were all 50V caps, though different manufacturers. > >Thanks all for the simple test setups. > >George H.-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 12:19:53 -0800 (PST), tabbypurr@gmail.com wrote:>On Friday, 16 November 2018 15:57:26 UTC, 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 > >Tantalums acquire microscopic defects due to soldering. These greatly reduce voltacity (or some similar word). Lack of any flexibility in the connections also causes this problem. To correct this, tants need a healing process after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage. > > >NTThat's absolutely something we don't want to do in production. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 16, 20182018-11-16
On Friday, 16 November 2018 21:51:36 UTC, gnuarm.del...@gmail.com wrote:> On Friday, November 16, 2018 at 2:19:58 PM UTC-6, tabby wrote: > > On Friday, 16 November 2018 15:57:26 UTC, 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 > > > > Tantalums acquire microscopic defects due to soldering. These greatly reduce voltacity (or some similar word). Lack of any flexibility in the connections also causes this problem. To correct this, tants need a healing process after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage. > > How slow is slow? What size resistor?those I don't know. I saw others had beaten me to it. You could find out with a bad batch.> I was thinking of incorporating this into the test procedure for a board using a tant cap that fails on first test far more often than other components. On second thought, without having a way to properly analyze the problem, maybe it's better to let the cap fail and be replaced. Fixing one short on a part may be setting it up for a later failure in the field??? > > Rick C.AIUI the reforming type process makes sure they're fully upto the job, untreated ones tend not to be. NT
Reply by ●November 16, 20182018-11-16
On Friday, 16 November 2018 22:05:42 UTC, John Larkin wrote:> On Fri, 16 Nov 2018 12:19:53 -0800 (PST), tabbypurr wrote: > >On Friday, 16 November 2018 15:57:26 UTC, John Larkin wrote: > >> On Fri, 16 Nov 2018 09:29:42 GMT, <698839253X6D445TD@nospam.org> > >> wrote:> >> >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 > > > >Tantalums acquire microscopic defects due to soldering. These greatly reduce voltacity (or some similar word). Lack of any flexibility in the connections also causes this problem. To correct this, tants need a healing process after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage. > > That's absolutely something we don't want to do in production.I was just wondering whether an instrument could do it itself as part of 1st boot. Perhaps in some cases. NT
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 14:16:31 -0800 (PST), tabbypurr@gmail.com wrote:>On Friday, 16 November 2018 22:05:42 UTC, John Larkin wrote: >> On Fri, 16 Nov 2018 12:19:53 -0800 (PST), tabbypurr wrote: >> >On Friday, 16 November 2018 15:57:26 UTC, John Larkin wrote: >> >> On Fri, 16 Nov 2018 09:29:42 GMT, <698839253X6D445TD@nospam.org> >> >> wrote: > >> >> >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 >> > >> >Tantalums acquire microscopic defects due to soldering. These greatly reduce voltacity (or some similar word). Lack of any flexibility in the connections also causes this problem. To correct this, tants need a healing process after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage. >> >> That's absolutely something we don't want to do in production. > >I was just wondering whether an instrument could do it itself as part of 1st boot. Perhaps in some cases. > > >NTI only use tantalums for their ESR, at the outputs of linear regulators, derated at least 3:1 on voltage. That seems reliable. Otherwise, I'd use ceramics or polymers and add ESR resistors or something to keep the regs happy. I recently did a 48-to-32 volt reg with an LM317HV, and did my ADJ node trick to stabilize that with ceramic output caps; otherwise I'd need a 100 volt tantalum. Regular aluminums are OK, just a bit big. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 15:48:46 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 11/16/18 2:46 PM, John Larkin wrote: >> On Fri, 16 Nov 2018 14:04:37 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 11/16/18 1:17 PM, John Larkin wrote: >>>> On Fri, 16 Nov 2018 12:01:23 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> 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 >>>> >>>> A cap from ADJ to ground seems to make an LM317 regulator ceramic cap >>>> tolerant. 10 nF is usually about right. I'd expect that to reduce HF >>>> noise a little. >>> >>> Interesting. Lead caps help buck switchers deal with large output caps, >>> but work the other way on 317s? >>> >>> Cheers >>> >>> Phil Hobbs >> >> https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?dl=0 >> >> https://www.dropbox.com/s/9q80heyfbwh5frp/317_comp.jpg?dl=0 >> >> 20 or 30 nF and no R6 works about as well. >> >> Lead caps work with switchers that have a fb pin that's ground >> referenced. I tried a cap across the upper divider resistor of a 317, >> and that makes ringing worse. The cap to ground was an empirical >> (fiddled) discovery. It actually works. >> >> I need to verify this for LM1117; we use a lot of those. >> >> I sometimes use a 317 with FB grounded, to make 1.25V for an ARM core. >> That doesn't work with my trick. > >No kidding? ;)There is a thing that works for 1.25V out, but it takes several parts. At 1.25v, a tantalum is fine. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●November 17, 20182018-11-17
tabbypurr wrote>Tantalums acquire microscopic defects due to soldering. These greatly reduce >voltacity (or some similar word). Lack of any flexibility in the connections >also causes this problem. To correct this, tants need a healing process >after soldering. This consists of slowly ramping up voltage in series with >a resistor. Do that & your tants should be reliable & nonexplosive at full >rated voltage.I often test new circuit prototypes on the lab supply with current limit set low by slowly turning up the voltage. Maybe that fixes the tantalums too.
