On 11/16/18 12:22 PM, 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. >>> >> >> 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. >>> 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%!You got snookered by the datasheet--those curves are almost always for 100 nF. You need the _characteristics_ link from the Digikey listing (if it's back up--they were all 404 when I looked a couple of days ago).> > Very good chance I'm doing something stupid. This is my test setup: > > https://imgur.com/a/x92g3iWThat's right. With time constants that large you'll need to wait several seconds between measurements, of course.> > I suppose it is possible the resistor on the right is affecting the readings from my LCR. Maybe I'm missing something else silly...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
X5R vs X7R MLCC
Started by ●November 14, 2018
Reply by ●November 16, 20182018-11-16
Reply by ●November 16, 20182018-11-16
On Friday, November 16, 2018 at 10:36:58 AM UTC-7, Phil Hobbs wrote:> On 11/16/18 12:22 PM, 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. > >>> > >> > >> 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. > >> > > > 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%! > > You got snookered by the datasheet--those curves are almost always for > 100 nF. You need the _characteristics_ link from the Digikey listing > (if it's back up--they were all 404 when I looked a couple of days ago). > > > > Very good chance I'm doing something stupid. This is my test setup: > > > > https://imgur.com/a/x92g3iW > > That's right. With time constants that large you'll need to wait > several seconds between measurements, of course. > > > > I suppose it is possible the resistor on the right is affecting the readings from my LCR. Maybe I'm missing something else silly... > > 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.comThat link still 404s for me. I would be very interested to get my hands on the 'characteristics' sheet. I indeed had to wait about 30 seconds between readings for things to settle. It will be interesting to compare with the new ones.
Reply by ●November 16, 20182018-11-16
On Fri, 16 Nov 2018 11:59:02 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> 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> > >Cheers > >Phil HobbsTantalums are erratic. Some later batch may behave/fail differently. -- 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 11/16/18 12:57 PM, DemonicTubes wrote:> On Friday, November 16, 2018 at 10:36:58 AM UTC-7, Phil Hobbs wrote: >> On 11/16/18 12:22 PM, 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?)>>>>>>> >>>>>>> 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. >>>>> >>>> >>>> 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. >>>> >> >>> 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%! >> >> You got snookered by the datasheet--those curves are almost always for >> 100 nF. You need the _characteristics_ link from the Digikey listing >> (if it's back up--they were all 404 when I looked a couple of days ago). >>> >>> Very good chance I'm doing something stupid. This is my test setup: >>> >>> https://imgur.com/a/x92g3iW >> >> That's right. With time constants that large you'll need to wait >> several seconds between measurements, of course. >>> >>> I suppose it is possible the resistor on the right is affecting the readings from my LCR. Maybe I'm missing something else silly... >>> That link still 404s for me. I would be very interested to get my hands on the 'characteristics' sheet.I reported it to Digikey. If enough people do that, they may take notice.> > I indeed had to wait about 30 seconds between readings for things to settle. > > It will be interesting to compare with the new ones. >Yup. To make it more interesting, makers use different numbers to refer to the same part, at least judging by the C(V) curves, which are exactly the same shape but cut off at different voltages, so that a 16V part loses 30% of its capacitance at 16V where the curve ends, and the 35V part has the same curve but continues down to -70% at 35V. Clear as mud, probably intentionally. 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 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 HobbsA 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. -- 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
Phil Hobbs wrote>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>Nice story, just learned something.
Reply by ●November 16, 20182018-11-16
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 -- 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 1:51 PM, 698839253X6D445TD@nospam.org wrote:> Phil Hobbs wrote >> 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> > > Nice story, just learned something. >Yeah, from back when you could learn something from EDN. :( 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 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 Hobbshttps://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. -- 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, 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. JL's worked fine... but I made a factor of two mistake in the math.. (I forgot the phase effects.) 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.
