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Old 23rd December 2013, 12:35 AM   #1191
jcx is offline jcx  United States
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the rising to the left "floor" often indicates a settling time tail 0 you need more accurate initial DC solution or to run the sim longer, just fft the last few 10 ms

do you have compression turned off? - add .option plotwinsize=0 to every schematic where you want good analysis resolution - because LT "SwitcherCAD" spice was designed initially with their switcing PS components in mind it uses lossy data compression as default assuming you would neede huge number of switching cycles for good sims
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Old 23rd December 2013, 08:30 AM   #1192
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Thanks, yes in every simulation I always include the ".option plotwinsize=0" directive...
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Old 1st February 2014, 11:59 AM   #1193
tvrgeek is offline tvrgeek  United States
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Plea for help
Ref:Help connection for Phase Measurement Post 29.

I am completely stuck on the TIAN probe implementation.
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Old 6th February 2014, 08:51 PM   #1194
tvrgeek is offline tvrgeek  United States
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Model files:
I was questioning some of the diode models as they seem too good. They are. So I exported the component file into EXCEL so I could sort them and take a good look at who has what specs. Lots of very "thin" models. I also added quite a few I found. Then I was able to export to a text file and poof! Spice could read the file just fine. Diodes are alphabetical now. Everything SPICE does an update, I'll have to do it again, but it is sure handy to have one simple file.
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Old 6th February 2014, 10:42 PM   #1195
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Quote:
Originally Posted by tvrgeek View Post
. . . Everything SPICE does an update, I'll have to do it again, but it is sure handy to have one simple file.
LTSpice actually does a good job at preserving a user's modifications and extensions to the installed component libraries when it updates. Even models you add to the "standard.xxx" database (standard.dio file, etc in the ./cmp/ directory) will be preserved through the update process.

Dale
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Old 6th February 2014, 11:19 PM   #1196
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Yes, but if you erase the bad models that come default with LTSpice it will put them back. If you REPLACE those models with good models, it will overwrite them with the bad ones. That's why I tried to make this file read-only once. That crashed LTSpice. Hopefully it is just a Linux issue though.

Furthermore, when it does it wipes out all the comments and text formatting so each model fits on one line. Did your models have info and copyright with them? OOPS!!! Gone. The only time this is not inconvenient is when you actually WANT to strip the formatting from a bunch of models - but that's rare.
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Old 7th February 2014, 06:15 PM   #1197
tvrgeek is offline tvrgeek  United States
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Originally Posted by dchisholm View Post
LTSpice actually does a good job at preserving a user's modifications and extensions to the installed component libraries when it updates. Even models you add to the "standard.xxx" database (standard.dio file, etc in the ./cmp/ directory) will be preserved through the update process.

Dale
Yes, very happy about that or I would keep all my added ones in a separate file. But it adds new ones on the end and cleans everything up. I find it easier if the list is alphabetical.
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Old 7th February 2014, 06:16 PM   #1198
tvrgeek is offline tvrgeek  United States
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It overwrites? Hmmm, that is not good. I have quite a few improved ones from newer vendor specs.
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Old 7th February 2014, 06:45 PM   #1199
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It would be nice if you would share any accurate models you have.

SPICE on transistors
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Old 8th February 2014, 06:24 AM   #1200
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Quote:
Originally Posted by keantoken View Post
Yes, but if you erase the bad models that come default with LTSpice it will put them back. If you REPLACE those models with good models, it will overwrite them with the bad ones . . . .
I wasn't aware of that behavior. I never tried replacing the supplied models with an improved model having the same name. I always added my own with some unique identifier. E.g., adding a model named "2N3904_CA" (for "Cordell Audio") rather than substituting Bob Cordell's parameters for whatever may be supplied as "standard" in LTSpice.

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Furthermore, when it does it wipes out all the comments and text formatting so each model fits on one line . . . .
I can't offer any suggestions about the formatting, but you can use the standard SPICE comment delimiter ( ";" ) to add any text you want to the end of a .MODEL statement. For example,
.MODEL 2N3904_CA NPN(IS=3.5e-15 BF=160 VAF=400 IKF=0.15 ISE=4e-16 NE=1.26 NF=1 RB=30.1 RC=1 RE=0.1 CJE=15e-12 MJE=0.25 VJE=0.75 CJC=3.6e-12 MJC=0.30 VJC=0.75 FC=0.5 TF=380e-12 XTF=30 VTF=4 ITF=0.4 TR=240e-9 BR=0.7 IKR=0 EG=1.1 XTB=1.5 XTI=3 NC=2 ISC=0 Vceo=40 Icrating=200m mfg=Bob_Cordell_Model) ; created February 24, 2011 copyright Cordell Audio
The update process retains the comments. Yeah, you have to open the "standard.*" file to see the information, but at least it's not lost entirely.

I certainly agree with one of your earlier comments: The lack of even a rudimentary capability to catalog and manage device models is a definite shortcoming in LTSpice. Such a capability should be even more essential in a commercial product development environment, where you might create many versions of a device's model to investigate the product's behavior not only with nominal parameters, but also with devices near the extremes of guaranteed values, combinations of HI/LO values among several devices, etc.

(I think the LTSpice developers want us to handle a situation like that by putting all the relevant models in a file, e.g. "Project_Name.mod" and then calling it out on the schematic as " .lib Project_Name.mod ". I don't recall the search hierarchy but I think the files called out in " .lib " statements are searched for particular device models before LTSpice looks at its "standard.xxx" files.)

Dale
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