On 02/22/2018 10:11 AM, John Larkin wrote:> On Sun, 18 Feb 2018 13:12:50 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 02/18/2018 08:14 AM, Chris Jones wrote: >>> On 17/02/2018 07:18, bloggs.fredbloggs.fred@gmail.com wrote: >>>> On Friday, February 16, 2018 at 12:51:24 PM UTC-5, John Larkin wrote: >>>>> On Fri, 16 Feb 2018 08:57:05 -0800 (PST), >>>>> bloggs.fredbloggs.fred@gmail.com wrote: >>>>> >>>>>> On Thursday, February 15, 2018 at 8:32:35 PM UTC-5, John Larkin wrote: >>>>>>> LM317's like some ESR in their output capacitors. I don't want any >>>>>>> electrolytic or tantalum caps in my new thing, just ceramics, and the >>>>>>> sim sure rings: >>>>>>> >>>>>>> https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?raw=1 >>>>>>> >>>>>>> But this fixes it: >>>>>>> >>>>>>> https://www.dropbox.com/s/9q80heyfbwh5frp/317_comp.jpg?raw=1 >>>>>>> >>>>>>> This ain't rocket science, but I haven't seen it done before. >>>>>> >>>>>> 317 needs no such ESR compensation. >>>>> >>>>> The data sheet says it does. >>>>> >>>>>> The ringing looks suspiciously like excitation of the SRF of an >>>>>> output capacitor. >>>>> >>>>> The frequency is low, and is different on the rising and falling edges >>>>> of the load current pulse. It's the chip pseudo-inductance resonating, >>>>> not the cap's ESL. If the ringing were local to the caps, my damping >>>>> on ADJ wouldn't fix that. >>>>> >>>>> Cap series L makes a different waveform than paralleled inductance. >>>>> >>>>> >>>>>> Did your model give it any ESL? And your solution merely reduces the >>>>>> shunt resistance by a factor of 20x which probably has more to do >>>>>> with damping than anything else. >>>>> >>>>> With a big cap from ADJ to ground, it rings badly, too. It has to be >>>>> the *right* capacitor to damp the ringing. >>>>> >>>>> I tried this with two different LM317 models; the ringing is somewhat >>>>> different (the LT317 is better), but the damping idea is the same. >>>>> >>>>> It's amazing that LT ever made a 317. I think they did that early on, >>>>> when they needed some revenue. They want $4 for it! I'm paying less >>>>> than a tenth of that for TI. >>>> >>>> I doubt you're going to see this energetic resonance on anything other >>>> than the LT part. >>>> >>> >>> I doubted it too, but found out the hard way when: >>> my 337's all oscillated, and >>> the 317s rang so badly that the oscillation ripple on the positive rails >>> was even bigger than on the negative rails. >>> >>> The 317s wouldn't oscillate by themselves, but they would ring like a >>> bell even after I cured the 337's of oscillation. >>> >>> I had to scratch off a lot of solder mask and tack on many tantalums to >>> cure my boards. Quite embarassing. >>> >>> >> Check out the Erroll Dietz article I posted upthread. > > He used three values of Cadj, 0, 10u, and 1000u. He didn't try > anything like 22nF. I'm sort of surprised that nobody seems to have > tried that, or at least publicized it.I expect that the required value will be pretty vendor-dependent. The Diodes TLV431 is very C-stable, but the TI one isn't, and the On Semi one is horrendous. 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 https://hobbs-eo.com
LM317 compensation
Started by ●February 15, 2018
Reply by ●February 22, 20182018-02-22
Reply by ●February 22, 20182018-02-22
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:> On 02/22/2018 01:54 AM, Steve Wilson wrote: >> Steve Wilson <no@spam.com> wrote:>>> Steve Wilson <no@spam.com> wrote: >>> Another aspect of op amps and linear regulators is the ouput >>> impedance. It often rises with frequency, giving an inductive >>> characteristic. There is a paper by Erroil H. Dietz, Senior >>> Technician, National Semiconductor titled "Understanding and Reducing >>> Noise Voltage on 3-Terminal Voltage Regulators" that describes this.>>> The article is very hard to find. Some pdf links have it inverted >>> which is a pain to have to rotate twice to read it.> I posted it upthread. It's on my website.> Cheers> Phil HobbsSo you're the guy who posts upside-down pdfs! Here it is, right-side up, OCR'd and reduced from 3,494,831 to 1,652,242 bytes: https://silvercell.000webhostapp.com/pdfs/dietz.pdf Please replace the one on your site so people can use it:)
Reply by ●February 22, 20182018-02-22
On Thursday, February 22, 2018 at 2:09:28 PM UTC-5, Steve Wilson wrote:> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > On 02/22/2018 01:54 AM, Steve Wilson wrote: > >> Steve Wilson <no@spam.com> wrote: > > >>> Steve Wilson <no@spam.com> wrote: > >>> Another aspect of op amps and linear regulators is the ouput > >>> impedance. It often rises with frequency, giving an inductive > >>> characteristic. There is a paper by Erroil H. Dietz, Senior > >>> Technician, National Semiconductor titled "Understanding and Reducing > >>> Noise Voltage on 3-Terminal Voltage Regulators" that describes this. > > >>> The article is very hard to find. Some pdf links have it inverted > >>> which is a pain to have to rotate twice to read it. > > > I posted it upthread. It's on my website. > > > Cheers > > > Phil Hobbs > > So you're the guy who posts upside-down pdfs!No you're just in the wrong hemisphere. :^) When I right click on a pdf I get the option to rotate CCW or CW, which is what I did.> > Here it is, right-side up, OCR'd and reduced from 3,494,831 to 1,652,242 > bytes: > > https://silvercell.000webhostapp.com/pdfs/dietz.pdf > > Please replace the one on your site so people can use it:)
Reply by ●February 22, 20182018-02-22
On 02/22/2018 02:09 PM, Steve Wilson wrote:> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 02/22/2018 01:54 AM, Steve Wilson wrote: >>> Steve Wilson <no@spam.com> wrote: > >>>> Steve Wilson <no@spam.com> wrote: >>>> Another aspect of op amps and linear regulators is the ouput >>>> impedance. It often rises with frequency, giving an inductive >>>> characteristic. There is a paper by Erroil H. Dietz, Senior >>>> Technician, National Semiconductor titled "Understanding and Reducing >>>> Noise Voltage on 3-Terminal Voltage Regulators" that describes this. > >>>> The article is very hard to find. Some pdf links have it inverted >>>> which is a pain to have to rotate twice to read it. > >> I posted it upthread. It's on my website. > >> Cheers > >> Phil Hobbs > > So you're the guy who posts upside-down pdfs! > > Here it is, right-side up, OCR'd and reduced from 3,494,831 to 1,652,242 > bytes: > > https://silvercell.000webhostapp.com/pdfs/dietz.pdf > > Please replace the one on your site so people can use it:) >Thanks! 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 https://hobbs-eo.com
Reply by ●February 23, 20182018-02-23
On Thu, 22 Feb 2018 07:11:41 -0800, John Larkin <jjlarkin@highlandtechnology.com> wrote:>On Sun, 18 Feb 2018 13:12:50 -0500, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>On 02/18/2018 08:14 AM, Chris Jones wrote: >>> On 17/02/2018 07:18, bloggs.fredbloggs.fred@gmail.com wrote: >>>> On Friday, February 16, 2018 at 12:51:24 PM UTC-5, John Larkin wrote: >>>>> On Fri, 16 Feb 2018 08:57:05 -0800 (PST), >>>>> bloggs.fredbloggs.fred@gmail.com wrote: >>>>> >>>>>> On Thursday, February 15, 2018 at 8:32:35 PM UTC-5, John Larkin wrote: >>>>>>> LM317's like some ESR in their output capacitors. I don't want any >>>>>>> electrolytic or tantalum caps in my new thing, just ceramics, and the >>>>>>> sim sure rings: >>>>>>> >>>>>>> https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?raw=1 >>>>>>> >>>>>>> But this fixes it: >>>>>>> >>>>>>> https://www.dropbox.com/s/9q80heyfbwh5frp/317_comp.jpg?raw=1 >>>>>>> >>>>>>> This ain't rocket science, but I haven't seen it done before. >>>>>> >>>>>> 317 needs no such ESR compensation. >>>>> >>>>> The data sheet says it does. >>>>> >>>>>> The ringing looks suspiciously like excitation of the SRF of an >>>>>> output capacitor. >>>>> >>>>> The frequency is low, and is different on the rising and falling edges >>>>> of the load current pulse. It's the chip pseudo-inductance resonating, >>>>> not the cap's ESL. If the ringing were local to the caps, my damping >>>>> on ADJ wouldn't fix that. >>>>> >>>>> Cap series L makes a different waveform than paralleled inductance. >>>>> >>>>> >>>>>> Did your model give it any ESL? And your solution merely reduces the >>>>>> shunt resistance by a factor of 20x which probably has more to do >>>>>> with damping than anything else. >>>>> >>>>> With a big cap from ADJ to ground, it rings badly, too. It has to be >>>>> the *right* capacitor to damp the ringing. >>>>> >>>>> I tried this with two different LM317 models; the ringing is somewhat >>>>> different (the LT317 is better), but the damping idea is the same. >>>>> >>>>> It's amazing that LT ever made a 317. I think they did that early on, >>>>> when they needed some revenue. They want $4 for it! I'm paying less >>>>> than a tenth of that for TI. >>>> >>>> I doubt you're going to see this energetic resonance on anything other >>>> than the LT part. >>>> >>> >>> I doubted it too, but found out the hard way when: >>> my 337's all oscillated, and >>> the 317s rang so badly that the oscillation ripple on the positive rails >>> was even bigger than on the negative rails. >>> >>> The 317s wouldn't oscillate by themselves, but they would ring like a >>> bell even after I cured the 337's of oscillation. >>> >>> I had to scratch off a lot of solder mask and tack on many tantalums to >>> cure my boards. Quite embarassing. >>> >>> >>Check out the Erroll Dietz article I posted upthread. > >He used three values of Cadj, 0, 10u, and 1000u. He didn't try >anything like 22nF. I'm sort of surprised that nobody seems to have >tried that, or at least publicized it.As I recall, from the time when I was actually checking transient response and output noise of commercial linear prototypes, the kudos for getting a 10n cap to do the job that a 10uF part was illustrated to do (or not to do) in the literature, wasn't worth mentioning. If it was, it was as the prelude to the inevitable 'Why not just leave it out? Nobody's going to do that anyways.' Tantalum caps were not even a consideration.....but the product still worked over the temperature range. With the harnessing involved, critical decoupling was always at the load, so my measurements on the output terminals were just 'nice to know' ~ required for a test spec or sales blurb. Power supplys were, and are still, just not sexy. RL
Reply by ●February 23, 20182018-02-23
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:> On 02/22/2018 02:09 PM, Steve Wilson wrote: >> So you're the guy who posts upside-down pdfs!>> Here it is, right-side up, OCR'd and reduced from 3,494,831 to 1,652,242 >> bytes:>> https://silvercell.000webhostapp.com/pdfs/dietz.pdf>> Please replace the one on your site so people can use it:)> Thanks!> Cheers> Phil HobbsI was browsing your website to try to find where you put your SED pdf files. I found https://electrooptical.net/SED, but there are no pdf files there. Can you include a link to that folder somewhere? I also found quite a few broken links. These have a bad effect in google searh since google will downgrade your site and put it at the bottom of the search rank. Broken links also affect user satisfaction since they can't find interesting files. You can check for broken links at a number of free online checkers, such as https://www.deadlinkchecker.com/ http://www.brokenlinkcheck.com/ https://www.deadlinkchecker.com/website-dead-link-checker.asp The top one is the best and fastest. I'm not sure if the nest two are actually the same site or not. Once you find broken links, you need to remove them from google search. There are lots of links that tell you how to do this. For example https://www.wantextra.com/remove-broken-links-google/
Reply by ●February 23, 20182018-02-23
Steve Wilson <no@spam.com> wrote:> I also found quite a few broken links. These have a bad effect in google > searh since google will downgrade your site and put it at the bottom of > the search rank. Broken links also affect user satisfaction since they > can't find interesting files.> You can check for broken links at a number of free online checkers, such > as> https://www.deadlinkchecker.com/> http://www.brokenlinkcheck.com/ > https://www.deadlinkchecker.com/website-dead-link-checker.asp> The top one is the best and fastest. I'm not sure if the nest two are > actually the same site or not.It turns out https://www.deadlinkchecker.com/ and https://www.deadlinkchecker.com/website-dead-link-checker.asp are actually the same site, but they give slightly different results. The bottom link seems to find a few more broken links. JL has some problems also, but these are mainly missing image links.
Reply by ●February 23, 20182018-02-23
Steve Wilson <no@spam.com> wrote:>> I also found quite a few broken links. These have a bad effect in google >> searh since google will downgrade your site and put it at the bottom of >> the search rank. Broken links also affect user satisfaction since they >> can't find interesting files.Actually, there's some positive feedback going on here. If google puts you at the bottom of the search results, then few people will visit your site. If few people visit your site, then google will put you at the bottom of the search results. So you get clobbered both ways.
Reply by ●February 23, 20182018-02-23
On Fri, 23 Feb 2018 11:54:48 GMT, Steve Wilson <no@spam.com> wrote:>Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 02/22/2018 02:09 PM, Steve Wilson wrote: >>> So you're the guy who posts upside-down pdfs! > >>> Here it is, right-side up, OCR'd and reduced from 3,494,831 to 1,652,242 >>> bytes: > >>> https://silvercell.000webhostapp.com/pdfs/dietz.pdf > >>> Please replace the one on your site so people can use it:) > >> Thanks! > >> Cheers > >> Phil Hobbs > >I was browsing your website to try to find where you put your SED pdf >files. I found https://electrooptical.net/SED, but there are no pdf files >there. Can you include a link to that folder somewhere? > >I also found quite a few broken links. These have a bad effect in google >searh since google will downgrade your site and put it at the bottom of the >search rank. Broken links also affect user satisfaction since they can't >find interesting files.He employs hunchbacks. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●February 23, 20182018-02-23
On 02/23/2018 09:44 AM, John Larkin wrote:> On Fri, 23 Feb 2018 11:54:48 GMT, Steve Wilson <no@spam.com> wrote: > >> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 02/22/2018 02:09 PM, Steve Wilson wrote: >>>> So you're the guy who posts upside-down pdfs! >> >>>> Here it is, right-side up, OCR'd and reduced from 3,494,831 to 1,652,242 >>>> bytes: >> >>>> https://silvercell.000webhostapp.com/pdfs/dietz.pdf >> >>>> Please replace the one on your site so people can use it:) >> >>> Thanks! >> >>> Cheers >> >>> Phil Hobbs >> >> I was browsing your website to try to find where you put your SED pdf >> files. I found https://electrooptical.net/SED, but there are no pdf files >> there. Can you include a link to that folder somewhere? >> >> I also found quite a few broken links. These have a bad effect in google >> searh since google will downgrade your site and put it at the bottom of the >> search rank. Broken links also affect user satisfaction since they can't >> find interesting files. > > He employs hunchbacks. > >An underrepresented minority. Watch out. 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 https://hobbs-eo.com
