LM317 compensation

[John Larkin]

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.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Tim Williams]

You can put resistors in series with ceramics...

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/

"John Larkin" <jjla...@highlandtechnology.com> wrote in message
news:vecc8dt14p89hcaeb...@4ax.com...

[John Larkin]

On Thu, 15 Feb 2018 19:46:44 -0600, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

>You can put resistors in series with ceramics...
>
>Tim

Sure, but that raises the bus impedance, and I expect load current
pulses. Putting resistors in series with just some of the caps still
rings.

This takes less parts. Actually, it's pretty good without R6.

[Tim Williams]

"John Larkin" <jjla...@highlandtechnology.com> wrote in message

news:t3ec8dppc7rm0hh03...@4ax.com...

> Sure, but that raises the bus impedance, and I expect load current
> pulses. Putting resistors in series with just some of the caps still
> rings.
>
> This takes less parts. Actually, it's pretty good without R6.

Well, your way raises the bus impedance rather more significantly.

You can't do "some", you need to do >2/3rds of total capacitance. Example:
3uF worth of 0.1's scattered around the board, 10uF + (0.1R or whatever
works best) "bulk" cap.

If you need low bus impedance, you have to do both!

[Lasse Langwadt Christensen]

Den fredag den 16. februar 2018 kl. 02.51.57 UTC+1 skrev John Larkin:
> On Thu, 15 Feb 2018 19:46:44 -0600, "Tim Williams"
> <tiw...@seventransistorlabs.com> wrote:
>
> >You can put resistors in series with ceramics...
> >
> >Tim
>
> Sure, but that raises the bus impedance, and I expect load current
> pulses. Putting resistors in series with just some of the caps still
> rings.
>
> This takes less parts. Actually, it's pretty good without R6.

from the data sheet:

The adjustment terminal can be bypassed to ground on the LM317-N to improve ripple rejection. This bypass
capacitor prevents ripple from being amplified as the output voltage is increased. With a 10-μF bypass capacitor,
80-dB ripple rejection is obtainable at any output level. Increases over 10 μF do not appreciably improve the
ripple rejection at frequencies above 120 Hz. If the bypass capacitor is used, it is sometimes necessary to
include protection diodes to prevent the capacitor from discharging through internal low current paths and
damaging the device.

[Phil Hobbs]

On 02/15/2018 08:32 PM, 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.
>
>

I do that reasonably routinely with LDOs and higher-current cap
multipliers--a zero-ohm jumper in series with the output cap to make it
look like we did it on purpose. ;)

With cap multipliers I usually put the resistor in series with the
output, but with LDOs I usually put it in series with the cap so that it
mimics a small ESR.

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

[bitrex]

On 02/15/2018 08:32 PM, 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.
>
>

Straight Darlington output emitter follower voltage regulators are meh,
maybe relics of when you couldn't make a decent high beta PNP on a chip

[Lasse Langwadt Christensen]

apart from the dropout, whats meh about them?

[bitrex]

All things being equal the quasi-complimentary/Sziklai topology is
better in just about all respects than the straight Darlington; the
complex output impedance of a straight Darlington has an inductive
component that increases rapidly with frequency (hence stability
problems), the complimentary less so

[John Larkin]

On Thu, 15 Feb 2018 18:05:23 -0800 (PST), Lasse Langwadt Christensen
<lang...@fonz.dk> wrote:

>Den fredag den 16. februar 2018 kl. 02.51.57 UTC+1 skrev John Larkin:
>> On Thu, 15 Feb 2018 19:46:44 -0600, "Tim Williams"
>> <tiw...@seventransistorlabs.com> wrote:
>>
>> >You can put resistors in series with ceramics...
>> >
>> >Tim
>>
>> Sure, but that raises the bus impedance, and I expect load current
>> pulses. Putting resistors in series with just some of the caps still
>> rings.
>>
>> This takes less parts. Actually, it's pretty good without R6.
>
>from the data sheet:
>
>The adjustment terminal can be bypassed to ground on the LM317-N to improve ripple rejection. This bypass

>capacitor prevents ripple from being amplified as the output voltage is increased. With a 10-?F bypass capacitor,
>80-dB ripple rejection is obtainable at any output level. Increases over 10 ?F do not appreciably improve the

>ripple rejection at frequencies above 120 Hz. If the bypass capacitor is used, it is sometimes necessary to
>include protection diodes to prevent the capacitor from discharging through internal low current paths and
>damaging the device.

Sure, everybody knows that. If you use a big cap from ADJ to ground,
and use low ESR output caps, it still rings wildly on a load step.

[John Larkin]

On Thu, 15 Feb 2018 21:19:21 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>On 02/15/2018 08:32 PM, 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.
>>
>>
>I do that reasonably routinely with LDOs and higher-current cap
>multipliers--a zero-ohm jumper in series with the output cap to make it
>look like we did it on purpose. ;)
>
>With cap multipliers I usually put the resistor in series with the
>output, but with LDOs I usually put it in series with the cap so that it
>mimics a small ESR.
>
>Cheers
>
>Phil Hobbs

Are you referring to the 1u resistor? That's just there to
conveniently snoop the current in the sim. It's the RC from ADJ to
ground that kills the ringing.

I expect big, fast current spikes in my load, so I don't want to add
ESR to my output bypass caps. Aluminums would have too much ESR
anyhow, but they would be too tall too.

[John Larkin]

I'm regulating +48 down to to +30, which few LDOs will do, and I have
the 317's in stock.

I thought this was a cute trick, but everybody's a critic.

[John Larkin]

The emitter follower is basically low output impedance. The PNP starts
with high output impedance. Sziklai types, like the LM1117, have
plenty of ESR constraints too. There are few regs around that are
stable down to zero ESR, and most are low-voltage parts.

The 1117 is a nice part, but limited to 15 volts in:out. (They
typically die around 60.)

Anyway, my thing seems to work. If you don't approve, don't use it.

[David Eather]

I have never heard of a 317 ringing in a properly designed real
application. Anyone seen it?

--
I look forward to the day when a chicken can cross the road without having
its motives questioned.

[bitrex]

A Sziklai output as I'm thinking of would have a PNP in line with the
output and an NPN driving the base; it would be the functional
equivalent of just a regular NPN emitter follower, "in disguise."

Unfortunately for high power regulators that's also a non-starter
because IIRC you can't make a high power monolithic PNP to pass the
current, either. It works pretty well with discretes.

As far as I can tell design work on high power non-LDO voltage
regulators ceased around 1980 they pretty much all seem to be variants
on the LMxxx LMxxxx topologies.

> The 1117 is a nice part, but limited to 15 volts in:out. (They
> typically die around 60.)
>
> Anyway, my thing seems to work. If you don't approve, don't use it.
>
>

Easy John Wayne, the LM317 is meatloaf not filet mignon but sometimes
meatloaf works just fine

[bitrex]

How would you know if one did? Do all LM317s communicate with u
telepathically

[pcdh...@gmail.com]

>Are you referring to the 1u resistor? That's just there to
>conveniently snoop the current in the sim. It's the RC from ADJ to
>ground that kills the ringing.

Normally a 317 running at high CL gain is pretty stable IME, but I can imagine that a bit of lead/lag could help the load transient response.

I use the lead network a bit like that in buck switchers with cap multipliers--take the DC feedback from the cap mult and AC from the switcher output.

Cheers

Phil Hobbs

[Kevin Aylward]

"John Larkin" wrote in message
news:vecc8dt14p89hcaeb...@4ax.com...

>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

Urhhhh...... the 1 uohm resister is finger nails down a blackboard for me.

For a regular spice engine on regular doubles, numbers can't span more than
12 digits and have it solve correctly. So, 1 uohm means 1 Meg max.

Don't use smaller than 1m ohm

er... This ain't rocket science.

And alternatively, ... you could put a low value resister in the ic output
prior to the feedback, and use a feedback cap direct from the ic output to
its input. Effectively, if configured correctly, the output resister does
the job of an out of loop esr, but without the dc error.

-- Kevin Aylward
http://www.anasoft.co.uk - SuperSpice
http://www.kevinaylward.co.uk/ee/index.html

[John Larkin]

One way to get a stiff programmable power rail is to drive the ADJ pin
of a 3T regulator with an opamp, open-loop. Maybe that could benefit
from some sort of damping too.

For a stiff bipolar rail, the TCA0372 opamp (dual, 1 amp per, 50
cents) is great, but it sure doesn't like low-ESR caps on its output.
A tenth of an ohm in series with the output fixes that.

[Lasse Langwadt Christensen]

that aussie guy had some fun with that recently

https://youtu.be/1VlKoR0ldIE

tldw: A new batch of boards with virtual ground made with an opamp oscillates
at certain loads, even though it has 270R resistor on the output. Turns out
the opamp with the same part number from a different manufacturer wasn't
quite identical

[John Larkin]

On Fri, 16 Feb 2018 06:51:47 -0500, bitrex

The 1117 is the opposite, a small PNP driving a big NPN follower. That
saves a junction drop. I call that an MDO, medium dropout regulator.
Its load ESR requirements are similar to a 317 type, I usually hang a
33 uF tantalum on an 1117, after which it's happy driving a bunch of
ceramic bypasses.

>
>Unfortunately for high power regulators that's also a non-starter
>because IIRC you can't make a high power monolithic PNP to pass the
>current, either. It works pretty well with discretes.

There are pfet-output LDOs.

>
>As far as I can tell design work on high power non-LDO voltage
>regulators ceased around 1980 they pretty much all seem to be variants
>on the LMxxx LMxxxx topologies.

Everything is going low-voltage, low loss, and switchers. And the 317
types work fine, except that there could be a version compensated for
ceramic caps.

[John Larkin]

On Fri, 16 Feb 2018 15:05:40 -0000, "Kevin Aylward"
<kevinR...@kevinaylward.co.uk> wrote:

>"John Larkin" wrote in message
>news:vecc8dt14p89hcaeb...@4ax.com...
>
>
>
>>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
>
>Urhhhh...... the 1 uohm resister is finger nails down a blackboard for me.

That's there to let me snoop the current. I find it hard to aim the LT
Spice current probe at device pins, so I'll stick in a resistor here
and there to make current snooping easy.

I usually use 1m, but I wanted an accurate sim of regulator ringing
and 1m might have affected that a little.

I suppose I could use 0 ohms... tries it... no, LT Spice will not
probe the current in a 0 ohm resistor. Pity.

>
>For a regular spice engine on regular doubles, numbers can't span more than
>12 digits and have it solve correctly. So, 1 uohm means 1 Meg max.

Looks like I should be OK here:

https://en.wikipedia.org/wiki/Double-precision_floating-point_format

In real life, PCB traces can be many milliohms. I have rarely used
them as current shunts.

>
>Don't use smaller than 1m ohm
>
>er... This ain't rocket science.
>
>And alternatively, ... you could put a low value resister in the ic output
>prior to the feedback, and use a feedback cap direct from the ic output to
>its input. Effectively, if configured correctly, the output resister does
>the job of an out of loop esr, but without the dc error.

A current snoop resistor could be on the input side too.

[bloggs.fred...@gmail.com]

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 ringing looks suspiciously like excitation of the SRF of an output capacitor. 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.

[Tim Williams]

<bloggs.fred...@gmail.com> wrote in message
news:d4f2ca9f-ff53-44fd...@googlegroups.com...

>317 needs no such ESR compensation. The ringing looks suspiciously like
>excitation of the SRF of an output capacitor. 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.
>

The output has an inductive characteristic at higher frequencies. It's
stable as you can see, but that doesn't mean the impedance is great.

[John Larkin]

On Fri, 16 Feb 2018 08:57:05 -0800 (PST),
bloggs.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.

[Long Hair]

John Larkin wrote:

> I suppose I could use 0 ohms... tries it... no, LT Spice will not
> probe the current in a 0 ohm resistor. Pity.

Don't jump so far. Try an order of magnitude at a time, and also
adjust read values according, of course.

Real current shunts are nice too. Especially for breadboard work.

[Phil Hobbs]

On 02/16/2018 10:24 AM, John Larkin wrote:
> On Fri, 16 Feb 2018 04:09:14 -0800 (PST), pcdh...@gmail.com wrote:
>
>>
>>> Are you referring to the 1u resistor? That's just there to
>>> conveniently snoop the current in the sim. It's the RC from ADJ to
>>> ground that kills the ringing.
>>
>> Normally a 317 running at high CL gain is pretty stable IME, but I can imagine that a bit of lead/lag could help the load transient response.
>>
>> I use the lead network a bit like that in buck switchers with cap multipliers--take the DC feedback from the cap mult and AC from the switcher output.
>>
>> Cheers
>>
>> Phil Hobbs
>
> One way to get a stiff programmable power rail is to drive the ADJ pin
> of a 3T regulator with an opamp, open-loop. Maybe that could benefit
> from some sort of damping too.

Yes, it's cheaper than an LM395 and works pretty well for that. The
compensation can be a bit squirrelly if the op amp is too fast or the
range of load currents is too wide.

>
> For a stiff bipolar rail, the TCA0372 opamp (dual, 1 amp per, 50
> cents) is great, but it sure doesn't like low-ESR caps on its output.
> A tenth of an ohm in series with the output fixes that.

Probably also a bit load sensitive, no?

Voltage references also vary widely in stability--the ON Semi version of
the TLV431 is unstable over most of the range you'd want to use it
in--check out Figure 18 at

<http://www.onsemi.com/pub/Collateral/TLV431A-D.PDF>

compared with the graph on P7 of

<https://www.diodes.com/assets/Datasheets/TLV431.pdf>.

Not exactly plug-in replacements!

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

[Phil Hobbs]

On 02/16/2018 12:19 PM, Tim Williams wrote:
> <bloggs.fred...@gmail.com> wrote in message
> news:d4f2ca9f-ff53-44fd...@googlegroups.com...
>> 317 needs no such ESR compensation. The ringing looks suspiciously
>> like excitation of the SRF of an output capacitor. 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.
>>
>
> The output has an inductive characteristic at higher frequencies.  It's
> stable as you can see, but that doesn't mean the impedance is great.
>
> Tim
>

See e.g. the Errol Dietz (*) article at

https://electrooptical.net/www/sed/ErrolDietzRegulatorNoisePeaks.pdf

Cheers

Phil Hobbs

(*) Errol Dietz rose from being Bob Pease's technician to National's
CTO. Not bad.

[bloggs.fred...@gmail.com]

On Friday, February 16, 2018 at 12:19:07 PM UTC-5, Tim Williams wrote:
> <bloggs.fred...@gmail.com> wrote in message
> news:d4f2ca9f-ff53-44fd...@googlegroups.com...
> >317 needs no such ESR compensation. The ringing looks suspiciously like
> >excitation of the SRF of an output capacitor. 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.
> >
>
> The output has an inductive characteristic at higher frequencies. It's
> stable as you can see, but that doesn't mean the impedance is great.

Right, any single pole rolloff has an effective inductance as output impedance, but the Q is generally too low (<1) to support ringing. His waveform shows a Q of approximately 10.

[bloggs.fred...@gmail.com]

I doubt you're going to see this energetic resonance on anything other than the LT part.

[Kevin Aylward]

"bitrex" wrote in message news:oBzhC.33534$iZ2....@fx29.iad...

Your 40 years out of date, probably.

Decent, high current, very fast complementary bipolar processes are
available.

The X-Fab XTO18 SOI is a pretty good 0.18u BiCMOS process. It has good low
noise mosfets and fully isolated, fast npn/pnp, and is very affordable.

[Kevin Aylward]

"John Larkin" wrote in message

news:k32e8d5g65854golt...@4ax.com...

On Fri, 16 Feb 2018 15:05:40 -0000, "Kevin Aylward"
<kevinR...@kevinaylward.co.uk> wrote:

>"John Larkin" wrote in message
>news:vecc8dt14p89hcaeb...@4ax.com...
>
>
>
>>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
>
>Urhhhh...... the 1 uohm resister is finger nails down a blackboard for me.

>That's there to let me snoop the current. I find it hard to aim the LT
>Spice current probe at device pins, so I'll stick in a resistor here
>and there to make current snooping easy.

>I usually use 1m, but I wanted an accurate sim of regulator ringing
>and 1m might have affected that a little.

>I suppose I could use 0 ohms... tries it... no, LT Spice will not
>probe the current in a 0 ohm resistor. Pity.

The "correct" way to probe currents in Spice if the data is not otherwise
available, is to use a zero voltage dc source.

In fact, in basic Spice3 AC currents are not available for say, bipolars, so
you have to do that if you want that data.

In SuperSpice to get transparent current probing in .subckts, I
automatically add 0V sources into the pins.

[John Larkin]

On Fri, 16 Feb 2018 20:21:56 -0000, "Kevin Aylward"

<kevinR...@kevinaylward.co.uk> wrote:

>"John Larkin" wrote in message
>news:k32e8d5g65854golt...@4ax.com...
>
>On Fri, 16 Feb 2018 15:05:40 -0000, "Kevin Aylward"
><kevinR...@kevinaylward.co.uk> wrote:
>
>>"John Larkin" wrote in message
>>news:vecc8dt14p89hcaeb...@4ax.com...
>>
>>
>>
>>>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
>>
>>Urhhhh...... the 1 uohm resister is finger nails down a blackboard for me.
>
>>That's there to let me snoop the current. I find it hard to aim the LT
>>Spice current probe at device pins, so I'll stick in a resistor here
>>and there to make current snooping easy.
>
>>I usually use 1m, but I wanted an accurate sim of regulator ringing
>>and 1m might have affected that a little.
>
>>I suppose I could use 0 ohms... tries it... no, LT Spice will not
>>probe the current in a 0 ohm resistor. Pity.
>
>The "correct" way to probe currents in Spice if the data is not otherwise
>available, is to use a zero voltage dc source.

OK, big round 0 ohm resistors!

--

John Larkin Highland Technology, Inc

picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

[bitrex]

I was going to ask what in the world is so special about a 317 that one
would need a gilded version of it

[John Larkin]

Only that LT Spice had a model already. I tried an independent LM317
model (can't recall where I got it) and the overall situation was
similar... lots of ringing with ceramic caps, and the right RC helped
a lot.

I'm borderline over using a switcher to get from +48 to +30. Not many
switchers will handle 48 in. We have LM2576HV in stock, an ancient 50
KHz SimpleSwitcher, which has its own issues, so I'll go linear and
dump the heat.

--

John Larkin Highland Technology, Inc

[Tim Williams]

<bloggs.fred...@gmail.com> wrote in message
news:fc7f7804-2fef-4483...@googlegroups.com...

>
> Right, any single pole rolloff has an effective inductance as output
> impedance, but the Q is generally too low (<1) to support ringing. His
> waveform shows a Q of approximately 10.
>

Right, so what does that tell you about the output impedance of the model in
question? :-)

(To go much farther, this thread needs waveforms from a real part. Or an
R+C and being done with it. ;-) )

[John Larkin]

On Fri, 16 Feb 2018 12:16:52 -0800 (PST),
bloggs.fred...@gmail.com wrote:

>On Friday, February 16, 2018 at 12:19:07 PM UTC-5, Tim Williams wrote:
>> <bloggs.fred...@gmail.com> wrote in message
>> news:d4f2ca9f-ff53-44fd...@googlegroups.com...
>> >317 needs no such ESR compensation. The ringing looks suspiciously like
>> >excitation of the SRF of an output capacitor. 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.
>> >
>>
>> The output has an inductive characteristic at higher frequencies. It's
>> stable as you can see, but that doesn't mean the impedance is great.
>
>Right, any single pole rolloff has an effective inductance as output impedance, but the Q is generally too low (<1) to support ringing. His waveform shows a Q of approximately 10.
>

Why would the Q be low? Active filters have Qs in the hundreds.

3T regulators are notorious for oscillating into low-ESR output caps.
Opamps, too. A minority of opamps are c-load stable, and that's
usually not determinable from the data sheets. Many opamps are stable
with small capacitive loads and with giant ones, unstable between.

My LT317 sim, without the fix, is starting to look decently damped
with 300,000 uF of zero-ESR caps. The internal pole must be a few 10s
of Hz.

--

John Larkin Highland Technology, Inc

[bloggs.fred...@gmail.com]

On Friday, February 16, 2018 at 6:32:58 PM UTC-5, John Larkin wrote:
> On Fri, 16 Feb 2018 12:16:52 -0800 (PST),
> bloggs.fred...@gmail.com wrote:
>
> >On Friday, February 16, 2018 at 12:19:07 PM UTC-5, Tim Williams wrote:
> >> <bloggs.fred...@gmail.com> wrote in message
> >> news:d4f2ca9f-ff53-44fd...@googlegroups.com...
> >> >317 needs no such ESR compensation. The ringing looks suspiciously like
> >> >excitation of the SRF of an output capacitor. 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.
> >> >
> >>
> >> The output has an inductive characteristic at higher frequencies. It's
> >> stable as you can see, but that doesn't mean the impedance is great.
> >
> >Right, any single pole rolloff has an effective inductance as output impedance, but the Q is generally too low (<1) to support ringing. His waveform shows a Q of approximately 10.
> >
>
> Why would the Q be low? Active filters have Qs in the hundreds.
>
> 3T regulators are notorious for oscillating into low-ESR output caps.
> Opamps, too. A minority of opamps are c-load stable, and that's
> usually not determinable from the data sheets. Many opamps are stable
> with small capacitive loads and with giant ones, unstable between.
>
> My LT317 sim, without the fix, is starting to look decently damped
> with 300,000 uF of zero-ESR caps. The internal pole must be a few 10s
> of Hz.

LOL- 300,000u ??? Hahaha- what does that tell you? The simulation is not credible.

[John Larkin]

On Fri, 16 Feb 2018 15:54:56 -0800 (PST),

bloggs.fred...@gmail.com wrote:

>On Friday, February 16, 2018 at 6:32:58 PM UTC-5, John Larkin wrote:
>> On Fri, 16 Feb 2018 12:16:52 -0800 (PST),
>> bloggs.fred...@gmail.com wrote:
>>
>> >On Friday, February 16, 2018 at 12:19:07 PM UTC-5, Tim Williams wrote:
>> >> <bloggs.fred...@gmail.com> wrote in message
>> >> news:d4f2ca9f-ff53-44fd...@googlegroups.com...
>> >> >317 needs no such ESR compensation. The ringing looks suspiciously like
>> >> >excitation of the SRF of an output capacitor. 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.
>> >> >
>> >>
>> >> The output has an inductive characteristic at higher frequencies. It's
>> >> stable as you can see, but that doesn't mean the impedance is great.
>> >
>> >Right, any single pole rolloff has an effective inductance as output impedance, but the Q is generally too low (<1) to support ringing. His waveform shows a Q of approximately 10.
>> >
>>
>> Why would the Q be low? Active filters have Qs in the hundreds.
>>
>> 3T regulators are notorious for oscillating into low-ESR output caps.
>> Opamps, too. A minority of opamps are c-load stable, and that's
>> usually not determinable from the data sheets. Many opamps are stable
>> with small capacitive loads and with giant ones, unstable between.
>>
>> My LT317 sim, without the fix, is starting to look decently damped
>> with 300,000 uF of zero-ESR caps. The internal pole must be a few 10s
>> of Hz.
>
>
>LOL- 300,000u ??? Hahaha- what does that tell you? The simulation is not credible.

It tells me that the 317 internal pole is at a few 10s of Hz. Most
opamps start to roll off at similar frequencies.

[George Herold]

How do you get 10Hz, 10^-2 sec. from 300uF? (where's the ~30 ohms)

I like your circuit, I've never had any issue's with the '317, but
I think I've always used it with a tant or Al cap.

George H.

[Tim Williams]

"George Herold" <ghe...@teachspin.com> wrote in message
news:80fce401-9ad3-4904...@googlegroups.com...

> How do you get 10Hz, 10^-2 sec. from 300uF? (where's the ~30 ohms)
>
> I like your circuit, I've never had any issue's with the '317, but
> I think I've always used it with a tant or Al cap.

Roughly speaking, if the control loop is dominant-pole compensated (it is,
more or less), then the controller has a phase shift of 90 degrees in the
cutoff band.

A pure integrator "plant" (the capacitor's impedance) has a phase shift of
90 degrees as well, hence oscillation (or at least something near it, give
or take accidental zeroes or additional poles, pushing it one way or the
other).

The only way to stabilize such a system is to push one pole up or down so
far that the other no longer has 90 degrees phase shift.

This is usually done by reducing C or adding R, restoring phase margin.
He's just demonstrating that it can be done the other way -- brute force.

In practice, a real 300mF (not uF, also, 10^-1 s) capacitor may have enough
ESR and ESL (including wiring) that its impedance is not actually that low,
even at low frequencies. Doesn't matter; the controller is theoretical (a
simple SPICE model), as is the capacitor, so it serves nicely to illustrate
theory rather than practice.

The 1 / (2*pi*(10Hz)*(0.3F)) ~= 0.05 ohms corresponds to...drumroll
please... the DC output resistance of the regulator, more or less. :-)

[George Herold]

Great, thanks Tim.

GH

[John Larkin]

On Fri, 16 Feb 2018 12:18:19 -0800 (PST),

The other LM317 sim rings more.


--

John Larkin Highland Technology, Inc trk

[John Larkin]

On Fri, 16 Feb 2018 22:05:34 -0600, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

>"George Herold" <ghe...@teachspin.com> wrote in message
>news:80fce401-9ad3-4904...@googlegroups.com...
>> How do you get 10Hz, 10^-2 sec. from 300uF? (where's the ~30 ohms)
>>
>> I like your circuit, I've never had any issue's with the '317, but
>> I think I've always used it with a tant or Al cap.
>
>Roughly speaking, if the control loop is dominant-pole compensated (it is,
>more or less), then the controller has a phase shift of 90 degrees in the
>cutoff band.
>
>A pure integrator "plant" (the capacitor's impedance) has a phase shift of
>90 degrees as well, hence oscillation (or at least something near it, give
>or take accidental zeroes or additional poles, pushing it one way or the
>other).
>
>The only way to stabilize such a system is to push one pole up or down so
>far that the other no longer has 90 degrees phase shift.
>
>This is usually done by reducing C or adding R, restoring phase margin.
>He's just demonstrating that it can be done the other way -- brute force.

A three-terminal regulator only has three pins to work with! I was
surprised that this worked.




--

John Larkin Highland Technology, Inc trk

[Phil Hobbs]

Of course the same is true of an op amp, if you ignore the power pins. ;)

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

[Tim Williams]

"Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message
news:p6a929$e7j$1...@dont-email.me...

>
> Of course the same is true of an op amp, if you ignore the power pins. ;)
>

Or a TL431, an op-amp so bad it has a fuckoff massive ~2.5V input offset
voltage, and no I_OH! ;-)

[John Larkin]

If you're going to get technical, and exclude power pins, an LM317
only has two pins. Or maybe one.

I hate it when people get technical.

[M Philbrook]

In article <p6acao$4k0$1...@dont-email.me>, tiw...@seventransistorlabs.com
says...

>
> "Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message
> news:p6a929$e7j$1...@dont-email.me...
> >
> > Of course the same is true of an op amp, if you ignore the power pins. ;)
> >
>
> Or a TL431, an op-amp so bad it has a fuckoff massive ~2.5V input offset
> voltage, and no I_OH! ;-)
>
> Tim

Hmm
"fuckoff" I don't remember learning about that metric when I was in
school some 45 years ago. my how you can fall behind if you don't pay
attention!

Jamie

[Long Hair]

John Larkin wrote:

> I hate it when people get technical.
>

You are supposed to like it. Another indicator that you chose the
wrong path. :-)

[Chris Jones]

On 16/02/2018 17:47, David Eather wrote:
> On Fri, 16 Feb 2018 14:46:33 +1000, John Larkin
> <jjla...@highlandtechnology.com> wrote:
>
>> On Thu, 15 Feb 2018 22:31:09 -0500, bitrex
>> <bit...@de.lete.earthlink.net> wrote:

>>
>>> On 02/15/2018 08:32 PM, 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.
>>>>
>>>>
>>>

>>> Straight Darlington output emitter follower voltage regulators are meh,
>>> maybe relics of when you couldn't make a decent high beta PNP on a chip
>>

>> I'm regulating +48 down to to +30, which few LDOs will do, and I have
>> the 317's in stock.
>>
>> I thought this was a cute trick, but everybody's a critic.
>>
>>
>
>
> I have never heard of a 317 ringing in a properly designed real
> application. Anyone seen it?
>

Yes, a 317 will ring with ceramic output capacitors, and a 337 will even
oscillate with ceramic output capacitors. (Unless you mean by "properly
designed" that it doesn't ring, in which case of course not.)

Can be cured with big tantalums on the output, or series resistors
between the regulator and output capacitors.

I guess this problem has not been well known in the past because in the
past it was very expensive to buy ceramic capacitors with high enough
values to replace the electrolytic output capacitor.

[Chris Jones]

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.

[John Larkin]

The other problem is that a minority of data sheets quantlfy cap ESR
requirements and effects, and many don't mention it at all, especially
older ones.

I derate tantalums 3:1 on voltage if they are on a bus with
significant current capability. That's not practical on a high-current
30 volt rail.

[John Larkin]

I can't persuade a TI LM317 to oscillate on a breadboard, with ceramic
caps, but it does ring.


--

[Phil Hobbs]

Check out the Erroll Dietz article I posted upthread.

[Tim Williams]

"M Philbrook" <jamie_...@charter.net> wrote in message
news:MPG.34f28ed5e...@news.eternal-september.org...

> "fuckoff" I don't remember learning about that metric when I was in
> school some 45 years ago. my how you can fall behind if you don't pay
> attention!

It's not quite as big as a metric shitload. :-)

[David Eather]

On Sun, 18 Feb 2018 23:08:55 +1000, Chris Jones <lugn...@spam.yahoo.com>
wrote:

OK. Something new I learnt about a chip I've used for years. By 'properly'
I only meant that it fulfilled the basic requirements laid out in the spec
sheet - and as was pointed out many older sheets have little to nothing to
say about the interactions of size and type of capacitor on the output.


--
I look forward to the day when a chicken can cross the road without having
its motives questioned.

[legg]

On Thu, 15 Feb 2018 17:32:30 -0800, John Larkin
<jjla...@highlandtechnology.com> 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.

The original LM117 data sheet shows a 10uF elec cap on the adjustment
pin, with its effect illustrated in the typical performance plots.

I don't know what the A version is intended to improve, but if you
vary from recommended decoupling, you're bound to see performance that
is non-optimal in some respect.

The fact that you're using ceramics simply by preference, may be the
only issue with this circuit. I don't know about the model, or what
you can expect from it, but you should probably suspect anything that
responds to 'tuning'.

RL

[Lasse Langwadt Christensen]

Den søndag den 18. februar 2018 kl. 14.09.05 UTC+1 skrev Chris Jones:
> On 16/02/2018 17:47, David Eather wrote:
> > On Fri, 16 Feb 2018 14:46:33 +1000, John Larkin
> > <jjla...@highlandtechnology.com> wrote:
> >
> >> On Thu, 15 Feb 2018 22:31:09 -0500, bitrex
> >> <bit...@de.lete.earthlink.net> wrote:
> >>
> >>> On 02/15/2018 08:32 PM, 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.
> >>>>
> >>>>
> >>>
> >>> Straight Darlington output emitter follower voltage regulators are meh,
> >>> maybe relics of when you couldn't make a decent high beta PNP on a chip
> >>
> >> I'm regulating +48 down to to +30, which few LDOs will do, and I have
> >> the 317's in stock.
> >>
> >> I thought this was a cute trick, but everybody's a critic.
> >>
> >>
> >
> >
> > I have never heard of a 317 ringing in a properly designed real
> > application. Anyone seen it?
> >
>
> Yes, a 317 will ring with ceramic output capacitors, and a 337 will even
> oscillate with ceramic output capacitors. (Unless you mean by "properly
> designed" that it doesn't ring, in which case of course not.)

afaict the LM337 is more like an LDO, output is collector rather than emitter

[Winfield Hill]

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:

I hate the way LTSpice hides added parasitic
elements, if any, to the passive components.
It's better to manually add these explicitly,
so others (and yourself) can see them, and
evaluate reasonableness of the chosen values.

John, please be aware that ceramic capacitors
certainly do not have zero esr. I measured
1210-size Murata, Samsung and Yageo caps, with
an HP 4192A LCR meter, and got values between
2.5 and 60 m-ohms for 47uF 16V caps at 5V bias,
and 9 to 30 m-ohms for 10uF 35V caps at 15V.
As expected for MLCC, the capacitance dropped
severely with voltage, but esr didn't change.

These resistances help to stabilize regulators
of all types, but also defeat ideal filtering.


--
Thanks,
- Win

[John Larkin]

Right. That makes it a current source, which forms an integrator into
low-ESR output caps.

[John Larkin]

On 19 Feb 2018 06:30:05 -0800, Winfield Hill

I'm expecting serious fast pulse loads, so I need to parallel a bunch
of ceramic caps at the regulator output. The load pulse rate could be
anything, so any ringing could explode. Adding the compensation parts
is good insurance.

Apparently physically bigger (like 1210) caps hold up better with
voltage, and may have lower ESR, so I'll use the biggest caps I can
reasonably fit.

[Winfield Hill]

John Larkin wrote...

Yes, I'm simply saying, when doing SPICE modeling
with MLCC caps, add some reasonable esr. Your LM317
exercises wold be more compelling if we knew the esr.
Maybe with an array of big ceramic caps, it wouldn't
matter much, but it's nice to see that parameter.


--
Thanks,
- Win

[Don Kuenz]

Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

> On 02/16/2018 12:19 PM, Tim Williams wrote:
>> <bloggs.fred...@gmail.com> wrote in message
>> news:d4f2ca9f-ff53-44fd...@googlegroups.com...

>>> 317 needs no such ESR compensation. The ringing looks suspiciously
>>> like excitation of the SRF of an output capacitor. 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.
>>>
>>

>> The output has an inductive characteristic at higher frequencies.\xc2\xa0 It's

>> stable as you can see, but that doesn't mean the impedance is great.
>>

> See e.g. the Errol Dietz (*) article at
>
> https://electrooptical.net/www/sed/ErrolDietzRegulatorNoisePeaks.pdf

That good little article just got squirreled away by me on my private
website. Dietz more-or-less suggests that designers use a tantalum
capacitor. And that's exactly what the wise guys did to the 7805 and
7812 on the PIC thermostat board that recently came under my purview.
Another article that got squirreled away (IIRC) argues against the
old "10uF and 0.1uF decoupling" rule-of-thumb. But, its exact location
eludes me at present. :(
You can blame it on my private website's perpetual reorg. But the
darned thing won't elude me for long.

Thank you,

--
Don Kuenz, KB7RPU
"To invent, you need a good imagination and a pile of junk"
- Thomas Alva Edison

[John Larkin]

On Mon, 19 Feb 2018 00:07:02 -0500, legg <le...@nospam.magma.ca> wrote:

>On Thu, 15 Feb 2018 17:32:30 -0800, John Larkin
><jjla...@highlandtechnology.com> 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.
>
>The original LM117 data sheet shows a 10uF elec cap on the adjustment
>pin, with its effect illustrated in the typical performance plots.
>
>I don't know what the A version is intended to improve, but if you
>vary from recommended decoupling, you're bound to see performance that
>is non-optimal in some respect.

What, me break rules? I would never do a thing like that.

>
>The fact that you're using ceramics simply by preference, may be the
>only issue with this circuit. I don't know about the model, or what
>you can expect from it, but you should probably suspect anything that
>responds to 'tuning'.
>
>RL

I have a load that goes from 0 to 12 amps in under 100 ns. I need a
bunch of ceramic caps to furnish that current without drooping much.

The 317 rings like a bell in that circuit. The added damping parts
clean that up beautifully. Actually, one 22nF cap from ADJ to ground
works great.

I don't want to use electrolytics for several reasons.

[Don Kuenz]

Don Kuenz <g...@crcomp.net> wrote:
>
> Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:
>> On 02/16/2018 12:19 PM, Tim Williams wrote:
>>> <bloggs.fred...@gmail.com> wrote in message
>>> news:d4f2ca9f-ff53-44fd...@googlegroups.com...
>>>> 317 needs no such ESR compensation. The ringing looks suspiciously
>>>> like excitation of the SRF of an output capacitor. 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.
>>>>
>>>

>>> The output has an inductive characteristic at higher frequencies. It's

>>> stable as you can see, but that doesn't mean the impedance is great.
>>>
>> See e.g. the Errol Dietz (*) article at
>>
>> https://electrooptical.net/www/sed/ErrolDietzRegulatorNoisePeaks.pdf
>
> That good little article just got squirreled away by me on my private
> website. Dietz more-or-less suggests that designers use a tantalum
> capacitor. And that's exactly what the wise guys did to the 7805 and
> 7812 on the PIC thermostat board that recently came under my purview.
> Another article that got squirreled away (IIRC) argues against the
> old "10uF and 0.1uF decoupling" rule-of-thumb. But, its exact location
> eludes me at present. :(
> You can blame it on my private website's perpetual reorg. But the
> darned thing won't elude me for long.

Oh yeah, it's all starting to come back to me now. :) There's an ancient
_Radio Shack, Voltage Regulator Handbook, National Semiconductor_ (1977)
on my shelf. Dietz is not mentioned as a contributor, so maybe he hadn't
become prominent yet.
The book's full of very old school big iron power supplies. Although
it neglects to specifically mention tantalum capacitors in its
"Capacitor Selection" sub-chapter it does note them on its typical
applications circuit diagrams.
This is a very interesting thread. The more my mind cogitates on it,
the more interesting it becomes. ;)

[Steve Wilson]

John Larkin <jjla...@highlandtechnology.com> wrote:

> I have a load that goes from 0 to 12 amps in under 100 ns. I need a
> bunch of ceramic caps to furnish that current without drooping much.

> The 317 rings like a bell in that circuit. The added damping parts
> clean that up beautifully. Actually, one 22nF cap from ADJ to ground
> works great.

> I don't want to use electrolytics for several reasons.

Is that 12 Amps, as in 12,000 mA?

If so, the LM317 is only a 1.5 Amp device and won't handle 12 A. You can
parallel a number of LM317's, such as in Fig. 22 of the datasheet at

http://www.ti.com/lit/ds/symlink/lm317.pdf

An alternative is to use an external pass transistor with a PNP driver,
such as in Fig. 23 of the same datasheet.

In either case, the circuit is different from the single LM317 you are
using to show ringing. You need to add the external circuits to show the
response.

In addition, the circuit you show at

https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?raw=1

switches from 30mA to 200mA using a pulse current source. The current
source may be giving misleading results because it is a high impedance.

You may need to use a switched resistive load to provide some damping. This
may have a significant effect on the ringing.

Note the load transient response in Figs 3 and 4 of the TI datasheet show a
considerably different response than your model.

Other manufacturer's versions of the LM317 may have a considerably
different response.

As in all modeling exercises, the results should be verified in actual
hardware.

[John Larkin]

On Wed, 21 Feb 2018 00:47:56 GMT, Steve Wilson <n...@spam.com> wrote:

>John Larkin <jjla...@highlandtechnology.com> wrote:
>
>> I have a load that goes from 0 to 12 amps in under 100 ns. I need a
>> bunch of ceramic caps to furnish that current without drooping much.
>
>> The 317 rings like a bell in that circuit. The added damping parts
>> clean that up beautifully. Actually, one 22nF cap from ADJ to ground
>> works great.
>
>> I don't want to use electrolytics for several reasons.
>
>Is that 12 Amps, as in 12,000 mA?

Yes.

>
>If so, the LM317 is only a 1.5 Amp device and won't handle 12 A. You can
>parallel a number of LM317's, such as in Fig. 22 of the datasheet at
>
>http://www.ti.com/lit/ds/symlink/lm317.pdf
>
>An alternative is to use an external pass transistor with a PNP driver,
>such as in Fig. 23 of the same datasheet.
>
>In either case, the circuit is different from the single LM317 you are
>using to show ringing. You need to add the external circuits to show the
>response.

The load is pulsed at a fairly low duty cycle, so the average current
is a few hundred mA. The ceramic caps provide the peak current and the
317 recharges them.

>
>In addition, the circuit you show at
>
>https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?raw=1
>
>switches from 30mA to 200mA using a pulse current source. The current
>source may be giving misleading results because it is a high impedance.

Amps are amps. The load step demonstrates the ringing, and the fix for
the ringing.

>
>You may need to use a switched resistive load to provide some damping. This
>may have a significant effect on the ringing.
>
>Note the load transient response in Figs 3 and 4 of the TI datasheet show a
>considerably different response than your model.

They probably use caps with a lot of ESR. And the models differ too.

>
>Other manufacturer's versions of the LM317 may have a considerably
>different response.

Probably.

>
>As in all modeling exercises, the results should be verified in actual
>hardware.

Sure, we intend to actually build it.

[Steve Wilson]

John Larkin <jjla...@highlandtechnology.com> wrote:

> On Wed, 21 Feb 2018 00:47:56 GMT, Steve Wilson <n...@spam.com> wrote:
>
>>John Larkin <jjla...@highlandtechnology.com> wrote:

>>If so, the LM317 is only a 1.5 Amp device and won't handle 12 A. You can
>>parallel a number of LM317's, such as in Fig. 22 of the datasheet at

>>http://www.ti.com/lit/ds/symlink/lm317.pdf

>>An alternative is to use an external pass transistor with a PNP driver,
>>such as in Fig. 23 of the same datasheet.

>>In either case, the circuit is different from the single LM317 you are
>>using to show ringing. You need to add the external circuits to show the
>>response.

> The load is pulsed at a fairly low duty cycle, so the average current
> is a few hundred mA. The ceramic caps provide the peak current and the
> 317 recharges them.

>>In addition, the circuit you show at

>>https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?raw=1

>>switches from 30mA to 200mA using a pulse current source. The current
>>source may be giving misleading results because it is a high impedance.

> Amps are amps. The load step demonstrates the ringing, and the fix for
> the ringing.

Your simulation shows considerably different ringing between current rise
and fall. So the currents matter.

You need to model the actual currents you are using. I suspect the idle
current may be much lower, and the actual charge current may be higher.

I'd be happier to see the results with a pulsed 100ns 12 Amp load. But I'd
get a more recent model. See the TI PSice model below.

>>You may need to use a switched resistive load to provide some damping.
>>This may have a significant effect on the ringing.

>>Note the load transient response in Figs 3 and 4 of the TI datasheet
>>show a considerably different response than your model.

> They probably use caps with a lot of ESR. And the models differ too.

You need to model the ESR.

Say the caps need to hold 0.1V drop for 100ns. The required capacitance is

i = c dv/dt
i dt = c dv
c = i * dt / dv
= 12 * 1e-7 / 0.1
= 12 uf

You can now calculate the max ESR for 0.1V drop:

R = E / I
= 0.1 / 12
= 8.33 milliohms

A bunch of parallel caps should do. But you need to specify the ESR in your
model.

>>Other manufacturer's versions of the LM317 may have a considerably
>>different response.

> Probably.

You can get the TI Unencrypted PSpice LM317 Model at

https://webench.ti.com/wb5/download/TI_Models_201802200508_00815.zip

Other TI Spice models are at

http://www.ti.com/spicerack

>>As in all modeling exercises, the results should be verified in actual
>>hardware.

> Sure, we intend to actually build it.

Let us know the results.

[John Larkin]

On Wed, 21 Feb 2018 01:54:05 GMT, Steve Wilson <n...@spam.com> wrote:

>John Larkin <jjla...@highlandtechnology.com> wrote:
>
>> On Wed, 21 Feb 2018 00:47:56 GMT, Steve Wilson <n...@spam.com> wrote:
>>
>>>John Larkin <jjla...@highlandtechnology.com> wrote:
>
>>>If so, the LM317 is only a 1.5 Amp device and won't handle 12 A. You can
>>>parallel a number of LM317's, such as in Fig. 22 of the datasheet at
>
>>>http://www.ti.com/lit/ds/symlink/lm317.pdf
>
>>>An alternative is to use an external pass transistor with a PNP driver,
>>>such as in Fig. 23 of the same datasheet.
>
>>>In either case, the circuit is different from the single LM317 you are
>>>using to show ringing. You need to add the external circuits to show the
>>>response.
>
>> The load is pulsed at a fairly low duty cycle, so the average current
>> is a few hundred mA. The ceramic caps provide the peak current and the
>> 317 recharges them.
>
>>>In addition, the circuit you show at
>
>>>https://www.dropbox.com/s/11b3w42nsvpliki/317_nocomp.jpg?raw=1
>
>>>switches from 30mA to 200mA using a pulse current source. The current
>>>source may be giving misleading results because it is a high impedance.
>
>> Amps are amps. The load step demonstrates the ringing, and the fix for
>> the ringing.
>
>Your simulation shows considerably different ringing between current rise
>and fall. So the currents matter.

Sure, the output transistor emitter has a very different impedance
from 30 to 200 mA. So the pole from that impedance into the ceramic
caps is different for the two currents.

[Steve Wilson]

John Larkin <jjla...@highlandtechnology.com> wrote:

> On Wed, 21 Feb 2018 01:54:05 GMT, Steve Wilson <n...@spam.com> wrote:
>>> Amps are amps. The load step demonstrates the ringing, and the fix for
>>> the ringing.

>>Your simulation shows considerably different ringing between current
>>rise and fall. So the currents matter.

> Sure, the output transistor emitter has a very different impedance
> from 30 to 200 mA. So the pole from that impedance into the ceramic
> caps is different for the two currents.

>>You need to model the actual currents you are using. I suspect the idle
>>current may be much lower, and the actual charge current may be higher.

>>I'd be happier to see the results with a pulsed 100ns 12 Amp load.

I did it for you. The compensation cap is critical and very different from
your result. See below.

>>>>You may need to use a switched resistive load to provide some damping.
>>>>This may have a significant effect on the ringing.

>>>>Note the load transient response in Figs 3 and 4 of the TI datasheet
>>>>show a considerably different response than your model.

>>> They probably use caps with a lot of ESR. And the models differ too.

>>You need to model the ESR.

>>Say the caps need to hold 0.1V drop for 100ns. The required capacitance
>>is

>> i = c dv/dt
>> i dt = c dv
>> c = i * dt / dv
>> = 12 * 1e-7 / 0.1
>> = 12 uf

>>You can now calculate the max ESR for 0.1V drop:

>> R = E / I
>> = 0.1 / 12
>> = 8.33 milliohms

>>A bunch of parallel caps should do. But you need to specify the ESR in
>>your model.

Version 4
SHEET 1 1184 680
WIRE 64 128 -96 128
WIRE 368 128 320 128
WIRE 400 128 368 128
WIRE 512 128 480 128
WIRE 624 128 512 128
WIRE 688 128 624 128
WIRE 752 128 688 128
WIRE 368 144 368 128
WIRE -96 160 -96 128
WIRE 512 160 512 128
WIRE 624 160 624 128
WIRE 192 256 192 224
WIRE 368 256 368 224
WIRE 368 256 192 256
WIRE -96 272 -96 240
WIRE 368 272 368 256
WIRE 512 272 512 224
WIRE 624 272 624 240
WIRE 192 288 192 256
WIRE 192 368 192 352
WIRE 368 384 368 352
WIRE 192 464 192 448
FLAG -96 272 0
FLAG 368 384 0
FLAG -96 128 IN
FLAG 512 272 0
FLAG 688 128 OUT
FLAG 624 272 0
FLAG 192 464 0
SYMBOL voltage -96 144 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 48
SYMBOL res 352 128 R0
SYMATTR InstName R1
SYMATTR Value 200
SYMBOL res 352 256 R0
SYMATTR InstName R2
SYMATTR Value 4.53k
SYMBOL LT317A 192 128 R0
SYMATTR InstName U1
SYMBOL cap 496 160 R0
SYMATTR InstName C1
SYMATTR Value 20uf
SYMBOL current 624 160 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName I1
SYMATTR Value PULSE(30m 200m 1m 1u 1u 4m)
SYMBOL cap 176 288 R0
SYMATTR InstName C2
SYMATTR Value 20n
SYMBOL res 176 352 R0
SYMATTR InstName R3
SYMATTR Value 20m
SYMBOL res 496 112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 1u
TEXT 72 -16 Left 2 !.tran 10m
TEXT 80 -40 Left 2 ;'LT317A Demo With Capacitive Load

[John Larkin]

On Wed, 21 Feb 2018 04:51:28 GMT, Steve Wilson <n...@spam.com> wrote:

>John Larkin <jjla...@highlandtechnology.com> wrote:
>
>> On Wed, 21 Feb 2018 01:54:05 GMT, Steve Wilson <n...@spam.com> wrote:
>>>> Amps are amps. The load step demonstrates the ringing, and the fix for
>>>> the ringing.
>
>>>Your simulation shows considerably different ringing between current
>>>rise and fall. So the currents matter.
>
>> Sure, the output transistor emitter has a very different impedance
>> from 30 to 200 mA. So the pole from that impedance into the ceramic
>> caps is different for the two currents.
>
>>>You need to model the actual currents you are using. I suspect the idle
>>>current may be much lower, and the actual charge current may be higher.
>
>>>I'd be happier to see the results with a pulsed 100ns 12 Amp load.
>
>I did it for you. The compensation cap is critical and very different from
>your result. See below.

That seems to be my sim; same currents, no ESR in the output cap, just
not as pretty. Any engineering doc should have a title, author, and
date.

I tried adding 20 mohms ESR to the output caps in my sim. Nothing
changed; it rings badly without the added compensation, and doesn't
ring with the RC, or just the C, from ADJ to ground.

Pulsing at 10 amps for 100 ns, the results are about the same: lots of
ringing, fixed by adding the same comps.

The compensation parts help.

>
>>>>>You may need to use a switched resistive load to provide some damping.
>>>>>This may have a significant effect on the ringing.
>
>>>>>Note the load transient response in Figs 3 and 4 of the TI datasheet
>>>>>show a considerably different response than your model.
>
>>>> They probably use caps with a lot of ESR. And the models differ too.
>
>>>You need to model the ESR.

You sure like to tell me what I need to do. But I don't report to you.

[Steve Wilson]

John Larkin <jjla...@highlandtechnology.com> wrote:

> On Wed, 21 Feb 2018 04:51:28 GMT, Steve Wilson <n...@spam.com> wrote:
>
>>John Larkin <jjla...@highlandtechnology.com> wrote:
>>
>>> On Wed, 21 Feb 2018 01:54:05 GMT, Steve Wilson <n...@spam.com> wrote:
>>>>> Amps are amps. The load step demonstrates the ringing, and the fix
>>>>> for the ringing.
>>
>>>>Your simulation shows considerably different ringing between current
>>>>rise and fall. So the currents matter.
>>
>>> Sure, the output transistor emitter has a very different impedance
>>> from 30 to 200 mA. So the pole from that impedance into the ceramic
>>> caps is different for the two currents.
>>
>>>>You need to model the actual currents you are using. I suspect the
>>>>idle current may be much lower, and the actual charge current may be
>>>>higher.
>>
>>>>I'd be happier to see the results with a pulsed 100ns 12 Amp load.
>>
>>I did it for you. The compensation cap is critical and very different
>>from your result. See below.
>
> That seems to be my sim; same currents, no ESR in the output cap, just
> not as pretty. Any engineering doc should have a title, author, and
> date.

Sorry, I picked the wrong file. You can see the original by changing the
current, pulse width and cap values as listed below.

This is a newsgroup discussion. The title is shown at the top of the
schematic. The date is the date of the post and is shown in the header. If
I put my name on the document, you will get pissed.

> I tried adding 20 mohms ESR to the output caps in my sim. Nothing
> changed; it rings badly without the added compensation, and doesn't
> ring with the RC, or just the C, from ADJ to ground.

> Pulsing at 10 amps for 100 ns, the results are about the same: lots of
> ringing, fixed by adding the same comps.

> The compensation parts help.

>>>>>>You may need to use a switched resistive load to provide some
>>>>>>damping. This may have a significant effect on the ringing.

>>>>>>Note the load transient response in Figs 3 and 4 of the TI datasheet
>>>>>>show a considerably different response than your model.

>>>>> They probably use caps with a lot of ESR. And the models differ too.

>>>>You need to model the ESR.

> You sure like to tell me what I need to do. But I don't report to you.

Sensitive? Not at all. Try the generic "you".

I increased the output cap from 12 uF to 20uF to match your value, amd
changed the pulse width from 100ns to 160ns to maintain the same dv.

The compensation cap was very difficult to optimize. You either get
underdamped with overshoot or overdamped with overshoot. But I ended up
with the same value as you - 20nF. So the response is sensitive to pulse
width, compensation cap and output cap values. Relatively small changes
have a big effect on the response.

The compensation cap ESR seems to have no effect. The output cap ESR has a
very significant effect on the shape of the response.

(I checked the title - this is the correct file. I need to always do that
in the future.)

SYMATTR SpiceLine Rser=8.33m

SYMBOL current 624 160 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName I1

SYMATTR Value PULSE(30m 12 5u 10n 10n 160n)

SYMBOL cap 176 288 R0
SYMATTR InstName C2
SYMATTR Value 20n
SYMBOL res 176 352 R0
SYMATTR InstName R3

SYMATTR Value 0

SYMBOL res 496 112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 1u

TEXT 72 -16 Left 2 !.tran 0 200u 0 50n
TEXT 80 -40 Left 2 ;'LT317A 12A Load Transient Response

[Phil Hobbs]

At the optimal compensation cap value, the results hardly depend on
pulse width at all.

I ran your sim with pulse widths from 50 ns to 1 us, and with a
compensation cap of 15 nF the droop is at most 70 mV over the whole
range, i.e. 0.23%, which isn't bad at all.

With no compensation cap, it's a mess for sure.

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

[Steve Wilson]

Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

> At the optimal compensation cap value, the results hardly depend on
> pulse width at all.

> I ran your sim with pulse widths from 50 ns to 1 us, and with a
> compensation cap of 15 nF the droop is at most 70 mV over the whole
> range, i.e. 0.23%, which isn't bad at all.

> With no compensation cap, it's a mess for sure.

> Cheers

> Phil Hobbs

I tried to keep the drop under 0.1V during the high current pulse. With 1us
pulse width, the drop calculates to

i = c dv/dt
i dt = c dv

dv = i * dt / c
= 12 * 1e-6 / 20e-6
= 0.6V

0.6 / 28 = 2.142e-2
= 2.142%

I measure 0.637V. This is

0.637 / 28 = 0.02275 = 2.275%

I don't know where you are measuring the drop. With 15nF compensation, the
peak current from the LT317A is 1.7A, a bit over the spec of 1.5A. The
recovery from the pulse is slow and draggy but probably acceptable at low
duty cycle.

Here's the file:

SYMATTR Value PULSE(30m 12 5u 10n 10n 1u)

SYMBOL cap 176 288 R0
SYMATTR InstName C2

SYMATTR Value 15n

[John Larkin]

If I modify someone else's sim or schematic, I show both names.

>
>> I tried adding 20 mohms ESR to the output caps in my sim. Nothing
>> changed; it rings badly without the added compensation, and doesn't
>> ring with the RC, or just the C, from ADJ to ground.
>
>> Pulsing at 10 amps for 100 ns, the results are about the same: lots of
>> ringing, fixed by adding the same comps.
>
>> The compensation parts help.
>
>>>>>>>You may need to use a switched resistive load to provide some
>>>>>>>damping. This may have a significant effect on the ringing.
>
>>>>>>>Note the load transient response in Figs 3 and 4 of the TI datasheet
>>>>>>>show a considerably different response than your model.
>
>>>>>> They probably use caps with a lot of ESR. And the models differ too.
>
>>>>>You need to model the ESR.
>
>> You sure like to tell me what I need to do. But I don't report to you.
>
>Sensitive? Not at all. Try the generic "you".
>
>I increased the output cap from 12 uF to 20uF to match your value, amd
>changed the pulse width from 100ns to 160ns to maintain the same dv.
>
>The compensation cap was very difficult to optimize. You either get
>underdamped with overshoot or overdamped with overshoot. But I ended up
>with the same value as you - 20nF. So the response is sensitive to pulse
>width, compensation cap and output cap values. Relatively small changes
>have a big effect on the response.
>
>The compensation cap ESR seems to have no effect. The output cap ESR has a
>very significant effect on the shape of the response.

If I put that extra 0805 cap on my PC board, I can elect to leave it
out, or to change its value if that improves transient response. But
just changing the ring Q from 20 to 2 is a big improvement. What I
don't want is the trigger rate (controlled by my cutomer) to push the
ringing into bad places.

This is, to me, a new way of using the LM317. I thought I'd share it.

[Steve Wilson]

John Larkin <jjla...@highlandtechnology.com> wrote:

> This is, to me, a new way of using the LM317. I thought I'd share it.

To me, it is amazing that a device can take such a horrible whacking and
recover so gracefully. This is in a device that has zero phase shift at DC
and a constant voltage difference between the output and the feedback pin.

Before we terrorize users with the response to transient pulses, the
behaviour is much more docile with softer loads. Here's the result with a
sine wave load. The behavior is very much the same with huge variations in
load and adj cap values and load current. It is very well behaved.

Version 4
SHEET 1 1184 680
WIRE 64 128 -96 128
WIRE 368 128 320 128
WIRE 400 128 368 128
WIRE 512 128 480 128
WIRE 624 128 512 128
WIRE 688 128 624 128
WIRE 752 128 688 128
WIRE 368 144 368 128
WIRE -96 160 -96 128
WIRE 512 160 512 128
WIRE 624 160 624 128

WIRE -96 272 -96 240

WIRE 512 272 512 224

WIRE 624 304 624 240
WIRE 192 336 192 224
WIRE 336 336 192 336
WIRE 368 336 368 224
WIRE 368 336 336 336
WIRE 368 352 368 336
WIRE 192 368 192 336
WIRE 624 400 624 384
WIRE 192 448 192 432
WIRE 368 464 368 432
WIRE 192 544 192 528
FLAG -96 272 0
FLAG 368 464 0

FLAG -96 128 IN
FLAG 512 272 0
FLAG 688 128 OUT

FLAG 192 544 0
FLAG 336 336 R1R2
FLAG 368 128 R1R4
FLAG 624 400 0

SYMBOL voltage -96 144 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1

SYMATTR Value 15

SYMBOL res 352 128 R0
SYMATTR InstName R1

SYMATTR Value 470
SYMBOL res 352 336 R0
SYMATTR InstName R2
SYMATTR Value 3242

SYMBOL LT317A 192 128 R0
SYMATTR InstName U1
SYMBOL cap 496 160 R0
SYMATTR InstName C1

SYMATTR Value 1u
SYMBOL cap 176 368 R0
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL res 176 432 R0
SYMATTR InstName R3
SYMATTR Value 20m

SYMBOL res 496 112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 1u

SYMBOL res 608 144 R0
SYMATTR InstName R5
SYMATTR Value 100
SYMBOL voltage 624 288 R0

WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2

SYMATTR InstName V2
SYMATTR Value SINE(0 1 1e3)
TEXT 72 -16 Left 2 !.tran 4m
TEXT 80 -40 Left 2 ;'LT317A Sine Wave Load

[Steve Wilson]

Steve Wilson <n...@spam.com> wrote:

> John Larkin <jjla...@highlandtechnology.com> wrote:

>> This is, to me, a new way of using the LM317. I thought I'd share it.

> To me, it is amazing that a device can take such a horrible whacking and
> recover so gracefully. This is in a device that has zero phase shift at
> DC and a constant voltage difference between the output and the feedback
> pin.

> Before we terrorize users with the response to transient pulses, the
> behaviour is much more docile with softer loads. Here's the result with
> a sine wave load. The behavior is very much the same with huge
> variations in load and adj cap values and load current. It is very well
> behaved.

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.

The article is also on p204 in Appendix C of Bob Pease's book titled
"Troubleshooting Analog Circuits". There is a a copy online. Scroll down to
page 204 to read it:

https://www.slideshare.net/jrbb2000/105768251-troubleshootinganalogcircuits

There is a series of Bob's articles at

http://www.introni.it/riviste_bob_pease.html

There is a possibility that the Dietz paper may be included in them, but it
will take a while to look for it.

[Steve Wilson]

Steve Wilson <n...@spam.com> wrote:

> Steve Wilson <n...@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.

> The article is also on p204 in Appendix C of Bob Pease's book titled
> "Troubleshooting Analog Circuits". There is a a copy online. Scroll down
> to page 204 to read it:

> https://www.slideshare.net/jrbb2000/105768251-troubleshootinganalogcircui
> ts

> There is a series of Bob's articles at

> http://www.introni.it/riviste_bob_pease.html

> There is a possibility that the Dietz paper may be included in them, but
> it will take a while to look for it.

Ha! There is a better source at

http://b-ok.org/book/767820/de94cb

It is on page 201. You need WinDjView to read it, which you can get at

https://windjview.sourceforge.io/

[Phil Hobbs]

On 02/22/2018 01:54 AM, Steve Wilson wrote:
> Steve Wilson <n...@spam.com> wrote:
>
>> Steve Wilson <n...@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.

[John Larkin]

On Sun, 18 Feb 2018 13:12:50 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>On 02/18/2018 08:14 AM, Chris Jones wrote:
>> On 17/02/2018 07:18, bloggs.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.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.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Phil Hobbs]

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.

[Steve Wilson]

Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

> On 02/22/2018 01:54 AM, Steve Wilson wrote:
>> Steve Wilson <n...@spam.com> wrote:

>>> Steve Wilson <n...@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:)

[George Herold]

On Thursday, February 22, 2018 at 2:09:28 PM UTC-5, Steve Wilson wrote:
> Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:
>
> > On 02/22/2018 01:54 AM, Steve Wilson wrote:
> >> Steve Wilson <n...@spam.com> wrote:
>
> >>> Steve Wilson <n...@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.

[Phil Hobbs]

Thanks!

[legg]

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

[Steve Wilson]

Phil Hobbs <pcdhSpamM...@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.

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/

[Steve Wilson]

Steve Wilson <n...@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.

[Steve Wilson]

Steve Wilson <n...@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.

[John Larkin]

On Fri, 23 Feb 2018 11:54:48 GMT, Steve Wilson <n...@spam.com> wrote:

>Phil Hobbs <pcdhSpamM...@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

[Phil Hobbs]

An underrepresented minority. Watch out.

[Steve Wilson]

Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

> On 02/23/2018 09:44 AM, John Larkin wrote:
>> He employs hunchbacks.

> An underrepresented minority. Watch out.

> Cheers

> Phil Hobbs

LOL. You guys are insane. Best laugh I've had all week.

Thanks

[Phil Hobbs]

On 02/23/2018 06:54 AM, Steve Wilson wrote:
> Phil Hobbs <pcdhSpamM...@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?

Yup.

>
> 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/
>
>

We recently switched the site from my classical hand-tooled artisanal
HTML (from an old family recipe) to some new-fangled Django thing that
only Dashing Firmware Hunchback understands. I'll mention it to him.

I found that all the links to the OldBooks directory (under
Resources->Good Books) don't work.

Any others?

Thanks

[John Larkin]

On Fri, 23 Feb 2018 10:11:05 -0500, Phil Hobbs

<pcdhSpamM...@electrooptical.net> wrote:

>On 02/23/2018 09:44 AM, John Larkin wrote:
>> On Fri, 23 Feb 2018 11:54:48 GMT, Steve Wilson <n...@spam.com> wrote:
>>
>>> Phil Hobbs <pcdhSpamM...@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

Sorry: spinally challenged.

[John Larkin]

On Fri, 23 Feb 2018 10:48:44 -0500, Phil Hobbs

The Brat did our web site in raw HTML.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Steve Wilson]

Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

> We recently switched the site from my classical hand-tooled artisanal
> HTML (from an old family recipe) to some new-fangled Django thing that
> only Dashing Firmware Hunchback understands. I'll mention it to him.

> I found that all the links to the OldBooks directory (under
> Resources->Good Books) don't work.

> Any others?

> Thanks

> Phil Hobbs

Your progress is amazing. Using

https://www.deadlinkchecker.com/website-dead-link-checker.asp

It found 598/598 URLs checked, 460 OK, 138 failed early this morning.

Just now, it found 416/416 URLs checked, 399 OK, 17 failed. Big change.

I found a ton using WinHTtrack, but it would take some time to get another
report and compare the results.

Some of the pages are nice. You are to be congratulated on your amazing
accomplishments. I don't think I've seen another website like yours.

[Steve Wilson]

John Larkin <jjla...@highlandtechnology.com> wrote:

> The Brat did our web site in raw HTML.

That's the best way I find. But I steer clear of the latest overblown CSS-
heavy HTML5 XHTML junk. I'm strictly HTML2 and find I can do just about
anything the latest overblown sites can do without the bloat. I'm also down
on using javascript to do fancy footwork with the pages. Just give me the
basic information I'm after and stop trying to make the site into a Youtube
animated video that wastes my time.

https://en.wikipedia.org/wiki/HTML

[John Larkin]

She said the worst part was making it work with Internet Explorer.

[Phil Hobbs]

On 02/23/2018 11:42 AM, Steve Wilson wrote:
> Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:
>
>> We recently switched the site from my classical hand-tooled artisanal
>> HTML (from an old family recipe) to some new-fangled Django thing that
>> only Dashing Firmware Hunchback understands. I'll mention it to him.
>
>> I found that all the links to the OldBooks directory (under
>> Resources->Good Books) don't work.
>
>> Any others?
>
>> Thanks
>
>> Phil Hobbs
>
> Your progress is amazing. Using
>
> https://www.deadlinkchecker.com/website-dead-link-checker.asp
>
> It found 598/598 URLs checked, 460 OK, 138 failed early this morning.
>
> Just now, it found 416/416 URLs checked, 399 OK, 17 failed. Big change.
>
> I found a ton using WinHTtrack, but it would take some time to get another
> report and compare the results.

Thanks. DFH found that the OldBooks directory had had its permission
changed, and there was some issue with all the phone number links (which
were the bulk of the failures).

Of the remaining five, four are external links that changed and there's
one missing link to our site.

>
> Some of the pages are nice. You are to be congratulated on your amazing
> accomplishments. I don't think I've seen another website like yours.
>

Thanks! It's been a good ride overall.

Cheers

[Sjouke Burry]

You are challenged by a Popey vegetable ??? Tssssskkkk.....

[Phil Hobbs]

Good point. I'll have to ask some Windows user to check ours out and
see--we're 100% linux round here.

Cheers