"Time step too small" errors have plagued SPICE users for half a century.? It is not easy to predict when they will happen, and can be even harder to eliminate them.
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Download the LTspice FAQ file.? Open it, and read until you find the section about "time step too small" errors.? Then read that section carefully.? It has a couple dozen things to TRY, in an attempt to get around the problem.? There are no guarantees. ?
Andy
?
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Such errors are difficult to resolve. In this
particular case, where an ADI schematic won't run. I suggest a
report to ADI's Engineer Zone. It should run in XVII, unless ADI
say it won't.
On 2025-02-26 14:02, ehernan3 via
groups.io wrote:
I
had downloaded the MAX44241 Spice model and Ltspice
schematic from Analog's website. For some reason I get the
following error message. " Analysis: Time step too small;
initial timepoint; trouble with u1: desd-instance d:u1:3 " I
didn't change anything within the model or schematic itself
so I'm not too sure why is occurred. Please note I am
limited to use Ltspice XVII and can't update my software to
LTspice 24, due to my company not approving that version of
the software. I was wondering if there is a work around to
get that error to not show up anymore and run without any
issues within LTspice XVII.
Link:?
--
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
|
I had downloaded the MAX44241 Spice model and Ltspice schematic from Analog's website. For some reason I get the following error message. " Analysis: Time step too small; initial timepoint; trouble with u1: desd-instance d:u1:3 " I didn't change anything within the model or schematic itself so I'm not too sure why is occurred. Please note I am limited to use Ltspice XVII and can't update my software to LTspice 24, due to my company not approving that version of the software. I was wondering if there is a work around to get that error to not show up anymore and run without any issues within LTspice XVII.
Link:?
|
Re: Frequency dependent common mode inductor
From (complete_reference):
Bxxx n1 n2 V=<expression>
Bxxx n1 n2 I=<expression> [Rpar=<value>] *[Cpar=<value>]
+ [[ic=<value>] tripdv=<value>] [tripdt=<value>]
+ [Laplace=<func(s)> [window=] [nfft=<num>] [mtol=<num>]]
* + [[units] Freq=<valuelist> [delay=<value>]] <=================
* + [NoJacob]
* Bxxx n1 n2 R=<expression>
* Bxxx n1 n2 P=<expression> [VprXover=<value>]
-marcel
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Re: Frequency dependent common mode inductor
I guess so. LTspice comes with lots of models for them from
Schaffner and Würth. Do you have a part number for yours?
F2 > [Contrib] > Schaffner > EMI
F2 > [Contrib] > Wurth > EMC-Components >
CommonMode_Chokes
Or you could try to make one from two coupled inductors. It's easier
than you probably thought.
Not quite so easy to tune it to exactly fit your table though, but
there's usually significant tolerance on EMC chokes, anyway.
--
Regards,
Tony
On 26/02/2025 08:55, F.an via groups.io
wrote:
toggle quoted message
Show quoted text
is it possible to build a "Frequency dependent common mode
inductor" in LTspice?
?
| f |
Ls |
Cs |
Rs |
| [HZ] |
[uH] |
[pF] |
[ohm] |
| 50 |
2040.3 |
4966800000 |
0.11861 |
| 100 |
2023.6 |
1251600000 |
0.13833 |
| 500 |
1997.3 |
50727000 |
0.47052 |
| 1000 |
1962.3 |
12905000 |
1.2977 |
| 5000 |
1636 |
619260 |
15.796 |
| 10000 |
1320.2 |
191850 |
36.245 |
| 50000 |
710.19 |
14266 |
144.23 |
| 100000 |
520.68 |
4864.9 |
247.12 |
| 500000 |
212.64 |
476.5 |
958.8 |
| 1000000 |
15.536 |
1631.6 |
1963.6 |
| 5000000 |
6.5795 |
154.02 |
79.92 |
|
Re: Frequency dependent common mode inductor
Yes, as a piece of circuit or a subcircuit.
But the data you have is all expressed in series component
terms, whereas the circuit needs, at least,? parallel resistance
and capacitance elements, which possibly could be calculated
from your data. Obviously, the inductor does not have a physical
series capacitor. Have you asked the manufacturer for a SPICE
(not 'LTspice') model?
On 2025-02-26 07:55, F.an via groups.io
wrote:
is it possible to build a "Frequency dependent common mode
inductor" in LTspice?
?
| f |
Ls |
Cs |
Rs |
| [HZ] |
[uH] |
[pF] |
[ohm] |
| 50 |
2040.3 |
4966800000 |
0.11861 |
| 100 |
2023.6 |
1251600000 |
0.13833 |
| 500 |
1997.3 |
50727000 |
0.47052 |
| 1000 |
1962.3 |
12905000 |
1.2977 |
| 5000 |
1636 |
619260 |
15.796 |
| 10000 |
1320.2 |
191850 |
36.245 |
| 50000 |
710.19 |
14266 |
144.23 |
| 100000 |
520.68 |
4864.9 |
247.12 |
| 500000 |
212.64 |
476.5 |
958.8 |
| 1000000 |
15.536 |
1631.6 |
1963.6 |
| 5000000 |
6.5795 |
154.02 |
79.92 |
--
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
|
Frequency dependent common mode inductor
is it possible to build a "Frequency dependent common mode inductor" in LTspice?
?
| f |
Ls |
Cs |
Rs |
| [HZ] |
[uH] |
[pF] |
[ohm] |
| 50 |
2040.3 |
4966800000 |
0.11861 |
| 100 |
2023.6 |
1251600000 |
0.13833 |
| 500 |
1997.3 |
50727000 |
0.47052 |
| 1000 |
1962.3 |
12905000 |
1.2977 |
| 5000 |
1636 |
619260 |
15.796 |
| 10000 |
1320.2 |
191850 |
36.245 |
| 50000 |
710.19 |
14266 |
144.23 |
| 100000 |
520.68 |
4864.9 |
247.12 |
| 500000 |
212.64 |
476.5 |
958.8 |
| 1000000 |
15.536 |
1631.6 |
1963.6 |
| 5000000 |
6.5795 |
154.02 |
79.92 |
|
Re: Monitor simulation percent completion from python
The expanded netlist returned few weeks ago in 24.1.3. It shows the components with their parameters immediately at the start of the simulation in the log file. But not the timing related parameters. All parameters are listed using .options logparams , but only when the simulation is finished.
?
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OOHH, thanks, I'll look into them....
Let's see if I can associate the symbol of an existing OP with the model I'm interested in, which is the MCP65R46.
|
On Tue, Feb 25, 2025 at 12:59 AM, eewiz wrote:
Subtracting 8ms from the start and stop values on the abscissa saw the plot window simply stop rendering in mid-redraw.
FYI, that is not what I suggested.? Leave the Start and Stop (or Left and Right) values alone.? Let LTspice figure them out on its own.? Change the text in the "Quantity Plotted" box.? THAT is the thing that shifts the entire waveform horizontally, shifting it so that time values that were near 8 ms, become near 0 seconds where resolution is better.? A picosecond out of 8 milliseconds is 0.125 part per billion.? A picosecond out of nanoseconds is a part per thousand.? Much less likely to be lost due to limited numerical precision.
?
But I suggested it only as a way to visually see smaller increments of time, which you do not need to do if you don't want to.
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The .raw file for the run is 11.5GB.
.SAVE might help.
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Before trying to shift the abscissa I did see that the values either side of 2.
With 15 digits, the values were much closer to 2 but still no 2.000000000000 value.
Of course you won't.? You 'never' will.? The chances are vanishingly small.
?
Keep these two fundamental principles in mind:
- SPICE/LTspice is a discrete time simulator.? There is no continuous time.
- .MEASURE is a POST-processing step.? All .MEAS commands are processed AFTER the simulation is over and done with.? It does not command the simulator to re-simulate until it finds the exact point where the voltage was 2.00000000000.? It interpolates between the closest simulated points that straddle it.? The chance that one of those simulated points hits 2.00000000000 volts exactly is astronomically small.? It will 'never' happen.
?
Therefore the effect, however it may be accomplished, is to print the time at which the next sample found is LESS-THAN 2 volts.
That is not what it does either.? It takes the two points that surround 2 V, and then it interpolates between them, to extract the time when a straight-line waveform would have crossed 2.0 V exactly.? That happens before the sample that was less than 2 V.
?
Wouldn't it be a phenomnal waste of processor time to interpolate between points, following the resultant curve, to find a point on that curve that is exactly 2.0000000000 volts when simply looking for the first value of data less-than 2 volts provides the same result.
It would not be a waste of time.? In your case, the difference between the interpolated time and the last simulated time might be mere nanoseconds, or who knows, femtoseconds?? But in another case it might be milliseconds or more.? LTspice always does the right thing, by interpolating and not ignoring the fact that waveforms take time to get from point A to point B.? Assuming that it ignores it would be wrong.
?
?
Regardless of how it is accomplished, the end result of using FALL=1 is to print the time at which the first data value less-than 2 is found.
That's incorrect.
?
Andy
?
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On Tue, Feb 25, 2025 at 05:43 AM, <j.bernabe1@...> wrote:
For example, I've opened (opamp2), how can I associate it to the library or file (. lib or . sub) ??? and how do I match the pins with their true function ??
There are two no, three things you should do:
- Verify that the comparator model's subcircuit has the same number of pins in the same order: In+ In- V+ V- OUT.
- Change (edit) the name next to the opamp2 symbol, from "opamp2", to the actual name of the subcircuit of your comparator.? The name of the subcircuit is the name that you see immediately after the command ".SUBCKT", when you examine the contents of the library file.? It is NOT the filename name of the file.
- Additionally, include the library file into the simulation, by adding this SPICE Directive anywhere on your schematic: ".lib filename.ext" where you use the actual filename.ext of the library file.? If that library file is not already in the same folder with the schematic, nor in one of your Model Library areas that you may have already set up in LTspice's Control Panel, then the filename should also have the relative or absolute path to the library file.
Some examples of (3) are:
- .lib MyComparator.lib
- .lib models\MyComparator.lib
- .lib ..\models\MyComparator.lib
- .lib \Mymodels\comparators\MyComparator.lib
- .lib "C:\Users\MyName\My Documents\My LTspice Models\comparators\MyComparator.lib"
?
Andy
?
|
On Tue, Feb 25, 2025 at 05:37 AM, <j.bernabe1@...> wrote:
help topics
About Ltspice
show change Log..
"Help topics" is the same as pressing F1.
?
Once the Help window opens up, there SHOULD be a column of contents on the left, and the main body on the right.? If you don't see the part on the left, then you might have clicked the "Hide" button along the top.? If so, click the "Show" button along the top.
?
Now that the Contents sub-window is present, select the "Contents" tab.? Then either click items one by one, or use Right-click > Open All, which opens up the entire Table of Contents.? From there, you can navigate to any of the Help pages.? They contain a lot of essential information for every LTspice user.
?
Andy
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Re: Issues running LTspice as a batch service
On Tue, Feb 25, 2025 at 08:32 PM, Jeff Kayzerman wrote:
.... Does anyone know why running in batch mode as a service account it would fail to look in the search paths?
This is only a guess here.? But I suspect you have defined User folders for your symbols and models, which reside in one of your account's folders, perhaps under its "Documents" folder or "AppData" or whatever.? The other account does not have the same folders.? Well, it has the same-named folders but they are distinct for each Windows user.? So it does not see the same library areas.
?
The settings in the .ini file are relative to each Windows account's folders, as managed by MS-Windows.? Windows does a good job of hiding their actual physical locations.
?
Andy
?
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Issues running LTspice as a batch service
I have a python program kicking off LTspice as a background windows process with the following command.
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process = await asyncio.create_subprocess_exec(LTSPICE_PATH, "-b", "-run", solverFlag, fpath, stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE)
?
I am running this process on a server and when I run it as my user account everything works as expected. Now I need to have it run as a windows service which requires a service account. I set this up and tried running but I get messages that symbols are missing from the simulation. I figured maybe the .ini file in the service account's folder was missing the symbol and library search paths so I made sure to match the .ini file in my service account's AppData/Roaming folder to match the one on my account. Unfortunately this did not help. Does anyone know why running in batch mode as a service account it would fail to look in the search paths?
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Re: Ltspice alternative for AD797
From the ADI data sheet: 110 MHz gain
bandwidth (G = 1000)
8 MHz bandwidth (G = 10)
On 2025-02-25 17:22, Andy I via
groups.io wrote:
On Tue, Feb 25, 2025 at 03:06 AM, john23 wrote:
Hello
, is there an alternative I could use for AD797 , LTspice
model will be best.
Have you tried the product selection guides, which most IC
vendors and many distributors offer on their websites?
The
model I got is very bad and its oscilating for no good
reason.
There probably is a reason.? It might be worth investigating
why.? High-bandwidth amps are more susceptible.? Maybe your
circuit into which you plugged the AD797 was the cause.
Gain
bandwidth: 100 MHz
-3
dB bandwidth: 8 MHz
Certainly that figure requires qualifications.? I know of no
op-amps that would have an 8 MHz open-loop -3dB bandwidth.? So
it is likely a closed-loop measure - and? then, at what
closed-loop gain is that measured?? It makes all the difference
in the world.
?
Andy
?
?
--
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 25/02/2025 10:28, Tony Casey wrote:
This
is also true with .MEAS. The time points are printed in single
precision in the logfile, by default. You can get double precision
by adding .option measdgt=15. This is true whether or not you also
use .option numdgt=15.
Having just installed V24.1.4, I noticed that:
.option measdgt=x
..appears to have been disabled, and doesn't appear to do anything
now - the .MEAS time points are now always double precision.
The log file content has changed a bit from 24.0.12 to 24.1.4. The
listed circuit is now the .net file instead of the .asc, and the
active .options are now listed, which is useful.
.option numdgt=x
..seems to works the same as before, but the raw files contents
differ slightly.
--
Regards,
Tony
|
On Tue, Feb 25, 2025 at 04:31 AM, John Woodgate wrote:
I suppose the OP posted more than one version of the .ASC. I don't think it's worth pursuing any further, but the fact that it runs OK with the simple opamp suggests that there is a problem with the AD757 model.
Or it suggests that there is a problem with THAT circuit when combined with a very wide-bandwidth op-amp like the AD797 (not 757).
?
The simple circuits I tried for the AD797 ran OK.
?
The fact that your schematic changes things, is indeed disturbing.
?
?
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Re: Ltspice alternative for AD797
On Tue, Feb 25, 2025 at 03:06 AM, john23 wrote:
Hello , is there an alternative I could use for AD797 , LTspice model will be best.
Have you tried the product selection guides, which most IC vendors and many distributors offer on their websites?
The model I got is very bad and its oscilating for no good reason.
There probably is a reason.? It might be worth investigating why.? High-bandwidth amps are more susceptible.? Maybe your circuit into which you plugged the AD797 was the cause.
Gain bandwidth: 100 MHz
-3 dB bandwidth: 8 MHz
Certainly that figure requires qualifications.? I know of no op-amps that would have an 8 MHz open-loop -3dB bandwidth.? So it is likely a closed-loop measure - and? then, at what closed-loop gain is that measured?? It makes all the difference in the world.
?
Andy
?
?
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Re: Monitor simulation percent completion from python
On Tue, Feb 25, 2025 at 02:51 AM, @HermanVos wrote:
For the percentage completion you need to decode the actual begin and end times from the .tran statements (assuming you do transient analysis of circuits). Sometimes these are straightforward and sometimes I see very interesting and complex constructions with formulas and .params.
I don't remember with certainty if this is true - but I believe the .TRAN command has numbers when you look at the expanded netlist.? In other words, the formulas have been evaluated.? That is true of most things (e.g., element values) in the expanded netlist.
?
Of course this assumes that you still have access to the expanded netlist, and newer versions of LTspice eliminated that option.
?
Andy
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Re: Estimating Base spreading resistance for a bipolar transistor via LTspice
When temperature increases, the current resulting from the
reverse-biased gate-drain junction increases exponentially, so
yes, noise increases with temperature.
Le 25/02/2025 à 16:36, Jack Walton via
groups.io a écrit?:
toggle quoted message
Show quoted text
I am wondering whether the noise at higher current values
won't be affected by the warming of the device.? I know this to
be a limiting affect for JFETs.
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John Woodgate
Tony Casey
F.an