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Old 20th May 2021, 11:08 AM   #1
dotneck335 is offline dotneck335  United States
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Default LTspice QNANA

Often when I run a .step param simulation, I get a "QNANA" error in one or more of the steps, even though they may be close together in value. How do I avoid this?
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Old 20th May 2021, 10:52 PM   #2
dotneck335 is offline dotneck335  United States
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I also find that the LTspice simulator sometimes does this with a fixed parameter, NOT stepped. Then if I change it by just a tad (~0.1, say), it will run fine. I don't understand this rather peculiar behavior. Anyone?
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Old 21st May 2021, 06:48 PM   #3
Ludus Tonalis is offline Ludus Tonalis  Europe
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I've never seen this in LTspice - but my understanding is that NAN stands for Not A Number. The last A may stand for Amps, i.e. there's a current generating the error. There's a thread about a QNANV error over at the users' group.

Last edited by Ludus Tonalis; 21st May 2021 at 06:53 PM.
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Old 22nd May 2021, 07:30 AM   #4
dotneck335 is offline dotneck335  United States
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"....my understanding is that NAN stands for Not A Number."


I understand that as well---so it cannot compute that particular circuit. But, as I said, if I change a value by even a small amount, and then run it again, sometimes (not always) it works fine---which makes no sense---there is no 'divide by zero' or other causes and nothing obvious to me that triggers this error.
Do you have a link to that users' group?
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Old 22nd May 2021, 07:36 AM   #5
Indiglo is offline Indiglo  Australia
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It might be this one - Ltspice User Group
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Old 22nd May 2021, 12:50 PM   #6
dotneck335 is offline dotneck335  United States
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I tried that group, and even signed up for it. But it doesn't seem to DO anything---clicking on any of the links on that page just loops you back to the same page over and over again. Is there a trick?
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Old 22nd May 2021, 01:01 PM   #7
Indiglo is offline Indiglo  Australia
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There's the messages link top left below the home icon, try clicking on that, you should then see the messages to the group, then at the top right will be the search box or try this direct link to the messages page. I'm not a member of that site so I don't know what happens when you sign-in.
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Old 22nd May 2021, 06:38 PM   #8
Ludus Tonalis is offline Ludus Tonalis  Europe
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Quote:
Originally Posted by dotneck335 View Post
"....my understanding is that NAN stands for Not A Number."


I understand that as well---so it cannot compute that particular circuit. But, as I said, if I change a value by even a small amount, and then run it again, sometimes (not always) it works fine---which makes no sense---there is no 'divide by zero' or other causes and nothing obvious to me that triggers this error.
Do you have a link to that users' group?
The link for the actual discussion of this error is
LTspice@groups.io | Issue with .#QNANV

Here's another one that mentions QNAN errors:
LTspice@groups.io | How to fine run simulation in LTspice with SiC SCT3022KL model ?

If you click on Messages on the home page and do a search for QNAN, a whole load of threads are listed that relate to this error.

Quote:
Originally Posted by dotneck335
I tried that group, and even signed up for it. But it doesn't seem to DO anything---clicking on any of the links on that page just loops you back to the same page over and over again. Is there a trick?"
I really can't imagine why you are having problems. Have you made it work now?
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Old 22nd May 2021, 06:45 PM   #9
kevinkr is offline kevinkr  United States
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LTspice QNANA
Might try asking this question in the LTSpice thread here:

Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
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Old 23rd May 2021, 06:10 AM   #10
dotneck335 is offline dotneck335  United States
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Thanks, Kevin---I did just that. We'll see if I get a usable response. Have you ever seen this result in any of your simulations?
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