Welcome Notice

Register Log in

LD1117 capacitor...

J

Jasen Betts

Guest
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.
 
J

John Larkin

Guest
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
 
R

Rich S

Guest
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 µF 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
 
F

Fred Bloggs

Guest
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
 
S

server

Guest
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.
 
F

Fred Bloggs

Guest
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.
 
S

server

Guest
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.
 
C

Charlie+

Guest
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+
 
S

server

Guest
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.
 
J

Jasen Betts

Guest
On 2021-11-27, jlarkin@highlandsniptechnology.com <jlarkin@highlandsniptechnology.com> wrote:
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.
Do i recall correctly that that trick is to stick three ohms of
resistance in series with the capacitor?



--
Jasen.
 
U

Uwe Bonnes

Guest
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 ---------
 
S

server

Guest
On Sat, 27 Nov 2021 22:37:23 -0000 (UTC), Jasen Betts
<usenet@revmaps.no-ip.org> wrote:

On 2021-11-27, jlarkin@highlandsniptechnology.com <jlarkin@highlandsniptechnology.com> wrote:
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.


Do i recall correctly that that trick is to stick three ohms of
resistance in series with the capacitor?
No. Why wreck a perfectly good capacitor?



--

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.
 
S

Spehro Pefhany

Guest
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?
Stick a few ohms 0603 resistor in series with the ceramic and be on
the safe side.

--
Best regards,
Spehro Pefhany
 
S

server

Guest
On Mon, 29 Nov 2021 09:07:55 -0500, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

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?

Stick a few ohms 0603 resistor in series with the ceramic and be on
the safe side.
I have boards with power pours, ceramic caps everywhere, and I don\'t
want to add ESR and ESL to every cap.

So hang a big tantalum on the output to damp things, or add one small
ceramic cap from the ADJ pin to ground.

https://www.dropbox.com/sh/3kc40u7evj5kz42/AACOPUL3V63PsEtN5l_w3pYga?dl=0




--

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.
 
P

Phil Hobbs

Guest
Spehro Pefhany wrote:
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?

Stick a few ohms 0603 resistor in series with the ceramic and be on
the safe side.
Provided it\'s pulse rated. An output short will dump the entire stored
energy of the cap into that poor resistor in a microsecond or so.

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
 
Toggle Sidebar

Welcome to EDABoard.com

Sponsor

Top