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LD1117 capacitor

Started by Jasen Betts November 23, 2021
The LD1117 data sheet makes no mention of what type of 10uF capacitor to
use at the output. is it stable with ceramic there or does it, like the
LM1117, need something with more ESR?

-- 
  Jasen.
On Wed, 24 Nov 2021 00:57:44 -0000 (UTC), Jasen Betts
<usenet@revmaps.no-ip.org> wrote:

>The LD1117 data sheet makes no mention of what type of 10uF capacitor to >use at the output. is it stable with ceramic there or does it, like the >LM1117, need something with more ESR?
That looks a lot like an LM1117. The LD data sheet shows polarized output caps. Bad data sheet, like most data sheets. It probably likes some ESR. Lag compensation is buried inside and a low ESR cap will add a second pole into the loop. Test one! Give it a load step and see how much it rings. I know a trick for using an LM1117 with ceramic caps. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
On Wednesday, November 24, 2021 at 1:01:06 AM UTC, Jasen Betts wrote:
> The LD1117 data sheet makes no mention of what type of 10uF capacitor to > use at the output. is it stable with ceramic there or does it, like the > LM1117, need something with more ESR? > > -- > Jasen.
Hi Jasen, the ST datasheet says: "Only a very common 10 &micro;F minimum capacitor is needed for stability." "High efficiency is assured by NPN pass transistor" "The adjustable LD1117 is pin to pin compatible with the other standard." (Coy reference to the LM317? LM1117?) These suggest to me a common Al-electro type. Nothing exotic. You are skeptical of this? Or, you really want to use a ceramic type? = RS
On Tuesday, November 23, 2021 at 8:25:20 PM UTC-5, John Larkin wrote:
> On Wed, 24 Nov 2021 00:57:44 -0000 (UTC), Jasen Betts > <use...@revmaps.no-ip.org> wrote: > > >The LD1117 data sheet makes no mention of what type of 10uF capacitor to > >use at the output. is it stable with ceramic there or does it, like the > >LM1117, need something with more ESR? > That looks a lot like an LM1117. The LD data sheet shows polarized > output caps. Bad data sheet, like most data sheets. > > It probably likes some ESR. Lag compensation is buried inside and a > low ESR cap will add a second pole into the loop. Test one! Give it a > load step and see how much it rings. > > I know a trick for using an LM1117 with ceramic caps.
Anything that self-resonates at 1MHz will keep the operation stable.
> > -- > > If a man will begin with certainties, he shall end with doubts, > but if he will be content to begin with doubts he shall end in certainties. > Francis Bacon
On Fri, 26 Nov 2021 07:29:01 -0800 (PST), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

>On Tuesday, November 23, 2021 at 8:25:20 PM UTC-5, John Larkin wrote: >> On Wed, 24 Nov 2021 00:57:44 -0000 (UTC), Jasen Betts >> <use...@revmaps.no-ip.org> wrote: >> >> >The LD1117 data sheet makes no mention of what type of 10uF capacitor to >> >use at the output. is it stable with ceramic there or does it, like the >> >LM1117, need something with more ESR? >> That looks a lot like an LM1117. The LD data sheet shows polarized >> output caps. Bad data sheet, like most data sheets. >> >> It probably likes some ESR. Lag compensation is buried inside and a >> low ESR cap will add a second pole into the loop. Test one! Give it a >> load step and see how much it rings. >> >> I know a trick for using an LM1117 with ceramic caps. > >Anything that self-resonates at 1MHz will keep the operation stable. >
Please draw that for us. An LM1117 instability is typically closer to 100 KHz. LM317 has similar dynamics, and there are (various) Spice models for 317. Both like a lot of ESR in their output caps, and my trick works for both. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
On Friday, November 26, 2021 at 11:01:31 AM UTC-5, jla...@highlandsniptechnology.com wrote:
> On Fri, 26 Nov 2021 07:29:01 -0800 (PST), Fred Bloggs > <bloggs.fred...@gmail.com> wrote: > > >On Tuesday, November 23, 2021 at 8:25:20 PM UTC-5, John Larkin wrote: > >> On Wed, 24 Nov 2021 00:57:44 -0000 (UTC), Jasen Betts > >> <use...@revmaps.no-ip.org> wrote: > >> > >> >The LD1117 data sheet makes no mention of what type of 10uF capacitor to > >> >use at the output. is it stable with ceramic there or does it, like the > >> >LM1117, need something with more ESR? > >> That looks a lot like an LM1117. The LD data sheet shows polarized > >> output caps. Bad data sheet, like most data sheets. > >> > >> It probably likes some ESR. Lag compensation is buried inside and a > >> low ESR cap will add a second pole into the loop. Test one! Give it a > >> load step and see how much it rings. > >> > >> I know a trick for using an LM1117 with ceramic caps. > > > >Anything that self-resonates at 1MHz will keep the operation stable. > > > Please draw that for us. An LM1117 instability is typically closer to > 100 KHz. > > LM317 has similar dynamics, and there are (various) Spice models for > 317. Both like a lot of ESR in their output caps, and my trick works > for both.
317 uses a completely different compensation. A SFR of 1MHz cuts in at 100kHz maximum.
> > > > > -- > > Father Brown's figure remained quite dark and still; > but in that instant he had lost his head. His head was > always most valuable when he had lost it.
On Fri, 26 Nov 2021 13:01:05 -0800 (PST), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

>On Friday, November 26, 2021 at 11:01:31 AM UTC-5, jla...@highlandsniptechnology.com wrote: >> On Fri, 26 Nov 2021 07:29:01 -0800 (PST), Fred Bloggs >> <bloggs.fred...@gmail.com> wrote: >> >> >On Tuesday, November 23, 2021 at 8:25:20 PM UTC-5, John Larkin wrote: >> >> On Wed, 24 Nov 2021 00:57:44 -0000 (UTC), Jasen Betts >> >> <use...@revmaps.no-ip.org> wrote: >> >> >> >> >The LD1117 data sheet makes no mention of what type of 10uF capacitor to >> >> >use at the output. is it stable with ceramic there or does it, like the >> >> >LM1117, need something with more ESR? >> >> That looks a lot like an LM1117. The LD data sheet shows polarized >> >> output caps. Bad data sheet, like most data sheets. >> >> >> >> It probably likes some ESR. Lag compensation is buried inside and a >> >> low ESR cap will add a second pole into the loop. Test one! Give it a >> >> load step and see how much it rings. >> >> >> >> I know a trick for using an LM1117 with ceramic caps. >> > >> >Anything that self-resonates at 1MHz will keep the operation stable. >> > >> Please draw that for us. An LM1117 instability is typically closer to >> 100 KHz. >> >> LM317 has similar dynamics, and there are (various) Spice models for >> 317. Both like a lot of ESR in their output caps, and my trick works >> for both. >317 uses a completely different compensation. A SFR of 1MHz cuts in at 100kHz maximum.
What's SFR? Would you please explain that last comment? -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
 On Wed, 24 Nov 2021 00:57:44 -0000 (UTC), Jasen Betts
<usenet@revmaps.no-ip.org> wrote as underneath :

>The LD1117 data sheet makes no mention of what type of 10uF capacitor to >use at the output. is it stable with ceramic there or does it, like the >LM1117, need something with more ESR?
Take a look at the Datasheet for the NCP1117, it has specific information on the cap types and ESR values. C+
On Sat, 27 Nov 2021 06:58:33 +0000, Charlie+ <charlie@xxx.net> wrote:

> On Wed, 24 Nov 2021 00:57:44 -0000 (UTC), Jasen Betts ><usenet@revmaps.no-ip.org> wrote as underneath : > >>The LD1117 data sheet makes no mention of what type of 10uF capacitor to >>use at the output. is it stable with ceramic there or does it, like the >>LM1117, need something with more ESR? > >Take a look at the Datasheet for the NCP1117, it has specific >information on the cap types and ESR values. C+
If you're powering ICs, logic or opamps or whatever, you would probably have a mess of low-ESR ceramic bypass caps scattered about the schematic. What works there is one tant or alum cap to furnish the bulk ESR, and then the ceramics. That's not on any data sheet, but it works. Or use my trick for all-ceramic loads. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Jasen Betts <usenet@revmaps.no-ip.org> wrote:
> > Do i recall correctly that that trick is to stick three ohms of > resistance in series with the capacitor? >
Three time 1 Ohm in parallel sounds better -- Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------