A beginner cannot know your intention, though.
On 2025-04-04 20:36, David Schultz via
groups.io wrote:
On
4/4/25 2:14 PM, John Woodgate wrote:
That is not very wise, because those nodes
can get re-allocated whenever a change is made to the .ASC. It's
much safer to name all the nodes, even just A, B, C ...
It was just an example of how to get a voltage difference. Not a
recommendation to use internally generated node names.
--
OOO - Own Opinions only
If something is true:
* as far as we know - it's science
*for certain - it's mathematics
*unquestionably - it's religion
|
Place cursor on the net, then CTRL-right click and select
Highlight from the drop-down pane. Use ESC to cancel.
On 2025-04-04 20:34, Bell, Dave via
groups.io wrote:
Related, there
apparently used to be a Ctrl-F search for net nets by name.
I am running XVII,
and that does nothing.
Also, found a hint
that maybe the search function was hiding under Tools, but
can¡¯t find it there.
AND, is there
(still?) a Highlight Nets function?
?
Dave
?
?
That
is not very wise, because those nodes can get re-allocated
whenever a change is made to the .ASC. It's much safer to
name all the nodes, even just A, B, C ...
On 2025-04-04 19:29, David Schultz via
groups.io wrote:
On 4/4/25 1:09 PM, Bell, Dave via
groups.io wrote:
<*expletive*>!
Well, currents are important to the analysis, so that¡¯s
something, but Power is, as well, and that needs
differential voltages.
V(N0001,N0002)
--
OOO - Own Opinions only If something is true: * as far as we
know - it's science *for certain - it's mathematics
*unquestionably - it's religion
--
OOO - Own Opinions only
If something is true:
* as far as we know - it's science
*for certain - it's mathematics
*unquestionably - it's religion
|
On 4/4/25 2:14 PM, John Woodgate wrote: That is not very wise, because those nodes can get re-allocated whenever a change is made to the .ASC. It's much safer to name all the nodes, even just A, B, C ...
It was just an example of how to get a voltage difference. Not a recommendation to use internally generated node names. -- David Schultz "The cheeper the crook, the gaudier the patter." - Sam Spade
|
Related, there apparently used to be a Ctrl-F search for net nets by name.
I am running XVII, and that does nothing.
Also, found a hint that maybe the search function was hiding under Tools, but can¡¯t find it there.
AND, is there (still?) a Highlight Nets function?
?
Dave
?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]>
On Behalf Of John Woodgate
Sent: Friday, April 04, 2025 12:15 PM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] .MEAS scripting
?
That is not very wise, because those nodes can get re-allocated whenever a change is made to the .ASC. It's much safer to name all the nodes, even just A, B, C ...
On 2025-04-04 19:29, David Schultz via groups.io wrote:
On 4/4/25 1:09 PM, Bell, Dave via groups.io wrote:
<*expletive*>!
Well, currents are important to the analysis, so that¡¯s something, but Power is, as well, and that needs differential voltages.
V(N0001,N0002)
--
OOO - Own Opinions only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion
|
That is not very wise, because those nodes can
get re-allocated whenever a change is made to the .ASC. It's
much safer to name all the nodes, even just A, B, C ...
On 2025-04-04 19:29, David Schultz via
groups.io wrote:
On
4/4/25 1:09 PM, Bell, Dave via groups.io wrote:
<*expletive*>!
Well, currents are important to the analysis, so that¡¯s
something, but Power is, as well, and that needs differential
voltages.
V(N0001,N0002)
--
OOO - Own Opinions only
If something is true:
* as far as we know - it's science
*for certain - it's mathematics
*unquestionably - it's religion
|
On 4/4/25 1:09 PM, Bell, Dave via groups.io wrote: <*expletive*>!
Well, currents are important to the analysis, so that¡¯s something, but Power is, as well, and that needs differential voltages.
V(N0001,N0002) -- David Schultz "The cheeper the crook, the gaudier the patter." - Sam Spade
|
<expletive>!
Well, currents are important to the analysis, so that¡¯s something, but Power is, as well, and that needs differential voltages.
Nets that are significant such as I/O pins are properly labelled, and there are three
logically separate sections, with named nets. I can go through the ¡°internal¡± nodes and assign names I guess.
10 < #nodes < 100 so it¡¯s not too onerous¡
?
Thanks!
Dave
?
?
?
Voltages are net (wire) properties.? You can refer to them only by netname.
Choose good (useful) netname.
|
Re: Simulation runs very slowly: test.asc
On 04/04/2025 18:14, Christopher Paul
via groups.io wrote:
Yes, and I¡¯m
not impressed with other aspects of their model, either. The notes
for the most advanced T.I. LM317A model I can find specifically
state that the model does not address PSRR. What other small
signal characteristics does it not address? I also noticed that
ADJ terminal¡¯s DC current is 0 rather than the datasheet¡¯s nominal
50uA.
I downloaded an LM317 unencrypted behavioural model from TI's
website today, and in the notes it makes no mention that PSRR is not
modelled. Looking through the code, I can see that it is modelled.
However, the PSRR isn't modelled at all versus output current or
output capacitor value. On that basis, I wouldn't use it. (I also
had to make a couple of changes to the model to get it to work at
all.)
I also have several other LM317 models, including one from Motorola,
which are transistor level models, and those definitely do model
PSRR, although there are variations between them.
They all show that you should use a minimum of about 47¦ÌF for the
output capacitor - preferably greater. The PSRR also improves
considerably if you if you add a smaller cap from "ADJ" to GND.
--
Regards,
Tony
|
Re: Simulation runs very slowly: test.asc
On Fri, Apr 4, 2025 at 12:14 PM, Christopher Paul wrote:
... By any chance do you know of models that can be relied upon to assess PSRR and output impedance?
I don't know how well this works, but....? In theory, if you can find a full transistor-level model for one, it ought to be reasonable for PSRR and Zout.? However, finding one could be a challenge.
?
Also, there are issues between the design or intended circuit, and the actual circuit including parasitics.? Not just talking about capacitance.? If I remember correctly, Hans Camenzind (creator of the 555) wrote pretty good of the differences between intended circuit and what you get when you put it in an IC wafer.
?
Andy
?
|
And by the way, "Add Traces" is the full list of names of things you can plot.? You can mix and match in algebraic formulas, but that is the full list.
?
Andy
|
Voltages are net (wire) properties.? You can refer to them only by netname.
?
Choose good (useful) netnames.
?
Andy
?
|
I have a fairly large model that I need to probe many of its components for Voltage, Current, and/or Power over a run period.
Not difficult once I get the syntax correct, for individual parts withy clear net names, but it gets hairy, or at least tedious, to build up the .meas statements for
many parts.
?
In the plot pane, in Add Traces, I see a syntax like ¡°Id(M1), Ie(Q1), I(u1:E1), etc.¡±
Is there a form of that for Voltages, referring to other component pin numbers, ¡°V(R1:1)¡± or the like?
?
Dave
?
|
Re: Simulation runs very slowly: test.asc
On Fri, Apr 4, 2025 at 09:14 AM, Christopher Paul wrote:
Thanks for sharing your knowledge about the LM317 models. By any chance do you know of models that can be relied upon to assess PSRR and output impedance?
nope ! -- just maybe the built in LT1086 matches it's d/s parameters of your interest (i never required such - yet)
|
Re: Simulation runs very slowly: test.asc
On 4/4/25 11:14 AM, Christopher Paul via groups.io wrote: Thanks for sharing your knowledge about the LM317 models. By any chance do you know of models that can be relied upon to assess PSRR and output impedance? Simulation is not the best way to do this. In simulations I never bother with voltage regulators, just using voltage sources. To find the performance of a LM317 requires testing with careful attention to detail. I know that was done at least once for a series of articles in The Audio Amateur way back in 1995. -- David Schultz "The cheeper the crook, the gaudier the patter." - Sam Spade
|
Re: Simulation runs very slowly: test.asc
also i used my own transistor LM317 model and
?
downloaded a
?
* RUC002N05 NMOSFET model
* Model Generated by ROHM
?
?? if you use such ¡ú it's an X type device ? . . . or the new ADi cracked LT? has one in it's standard.mos library
|
Re: Simulation runs very slowly: test.asc
Yes, and I¡¯m not impressed with other aspects of their model, either. The notes for the most advanced T.I. LM317A model I can find specifically state that the model does not address PSRR. What other small signal characteristics does it not address? I also noticed that ADJ terminal¡¯s DC current is 0 rather than the datasheet¡¯s nominal 50uA. ? Not sure what ¡°? ideal shared/common/not-uncoupled supply¡° means. The supply is a simple, ideal voltage source. I measure no current through it since doing so could not distinguish between the loads from the several circuits. ? The op amps control small signal MOSFETs and translate voltages at their non-inverting inputs to precise, high-impedance current sources at the MOSFET¡¯s drains to control the higher currents output by the LM317¡¯s. ? Thanks for sharing your knowledge about the LM317 models. By any chance do you know of models that can be relied upon to assess PSRR and output impedance? ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Rene via groups.io
Sent: Friday, April 4, 2025 11:57 AM
To: [email protected]
Subject: Re: [LTspice] Simulation runs very slowly: test.asc? it's mostly the Ti?s LDO causing spurious fuzz at startup and later attempting to hang the spice engine . . . ? ideal shared/common/not-uncoupled supply ADi?s Op Amp looks mostly ok ? what is that you attempt to adjust with Op Amp ?
|
Re: 20nm PTM file not working in LTspice
On Fri, Apr 4, 2025 at 11:34 AM, John Woodgate wrote:
I understand, but LTspice Help doesn't even mention the possibility of a print step parameter.
It does, but it is easily missed:
Syntax:?.TRAN <Tstep> <Tstop> [Tstart [dTmax]] [modifiers]
????????.TRAN <Tstop> [modifiers]
The first form is the traditional .tran SPICE command. Tstep is the plotting increment for the waveforms but is also used as an initial step-size guess. LTspice uses waveform compression, so this parameter is of little value and can be omitted or set to zero.
?
In the Simulation Command editor, it labels it "Tprint" rather than "Tstep".? It is the same thing.
?
I had forgotten that LTspice can use that parameter as a first-guess for the internal Timestep.
?
IMO, it is not because of waveform compression that LTspice otherwise does not use Tprint or Tstep.? It's because that parameter was the step size for the line-printer output, which LTspice does not do.
?
Andy
?
|
Re: Simulation runs very slowly: test.asc
it's mostly the Ti?s LDO causing spurious fuzz at startup and later attempting to hang the spice engine . . .
?
? ideal shared/common/not-uncoupled supply
?
ADi?s Op Amp looks mostly ok
?
? what is that you attempt to adjust with Op Amp ?
|
Re: 20nm PTM file not working in LTspice
I notice that the 20 nm model file specifies:
+lmin ? ?= 1e-008 ? ? ? ? ?lmax ? ?= 2.4e-008 ? ? ?
?
This tells me that the model does use MKS dimensions, and your MOSFET sizes must be specified in units of meters, not microns.? To make that work, you would need to edit every MOSFET symbol on the schematic and change the L and W and PD and PS values from microns to meters.
L=0.18 --> WRONG
L=0.18u --> OK
?
You would need to do that in any simulator.
?
The same is most likely true of the 180 nm models too.? Although it does not have LMIN and LMAX parameters, the default dimensions are most likely Meters, not Microns, because SPICE's standard is Meters.? If you simulated it with values like 0.18, it would have simulated incorrectly.
?
Andy
?
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Re: 20nm PTM file not working in LTspice
On Fri, Apr 4, 2025 at 11:25 AM, Say Die. wrote:
I just gave you the basic idea so you can find it easily. ?
"Basic idea" is not enough.? If you did that with LTspice, it would give you an error.? Filenames have extensions, and the extension must be included.
?
Andy
?
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John Woodgate
Bell, Dave
Tony Casey
Rene