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SPICE model for a 74LS14

ljcox

Well-Known Member
Does anyone know where I can find one? I've tried the Fairchild and Texas Inst sites but to no avail.

Thanks
 

Roff

Well-Known Member
ljcox said:
Does anyone know where I can find one? I've tried the Fairchild and Texas Inst sites but to no avail.

Thanks
Len, if you want it for SwCAD, I can show you how to set up the Schmitt trigger that's in the digital library to do a fair emulation of a 74LS14. Or you might figure it out for yourself. :D
 

Roff

Well-Known Member
ljcox said:
Ron,
I looked at it but could not see how to do it. So please advise.
OK, place a Schmitt trigger on the schematic and right-click on it. Below is a screen capture of this. I parameterized the logic high voltage as an example. You could just make it 4, or 5, or whatever you think is right. I also picked typical values for delay, rise time, threshold voltage, and hysteresis. You can get them from the datasheet. If you want to add input and output resistance and capacitance, you will have to add them externally.
This model is only behavioral, but is still very useful, and runs very fast.
You can, of course, do similar setups with any of the digital parts. The D FF is very useful. I made a model of a 4-bit counter using these models,and it matched the CMOS part (can't remember which one, and I think it's on my computer at work) pretty well.
 

Attachments

Roff

Well-Known Member
ljcox said:
Thanks Ron, much appreciated.

I'll hopefully be able to do it myself in the future.
Len, I hope I didn't leave the impression that I'm reluctant to help. I guess I get my strokes this way. :lol:
Does the behavioral model meet your needs?
 

ljcox

Well-Known Member
No Ron, I did not mean to imply that. I meant that I want to be able to learn how to write the models myself so, eventually, I don't need to ask.

But I expect I'll need more tuition yet.

I have not looked at the model yet, the garden & gardener (wife) await my attention.
 

Roff

Well-Known Member
ljcox said:
No Ron, I did not mean to imply that. I meant that I want to be able to learn how to write the models myself so, eventually, I don't need to ask.

But I expect I'll need more tuition yet.

I have not looked at the model yet, the garden & gardener (wife) await my attention.
I should move to Oz this time of year. The temperature got all the way up to -2C today here in Boise. Garden, indeed! :x
 

ljcox

Well-Known Member
Ron,
In Melbourne, we don't have -2C even in winter. When I extracted myself from the garden, I fooled with SwCAD. Two questions:-

1. I inserted your model, but I can't see how to specify Vcc - see the screen dump below.

2. I read the help about mutual inductance, it said to use this format:- K1 L1 L2 1 but can't see how to input this data.

I assume that L1 and L2 are drawn in the normal way and then the Mutual Inductance parameters are input to connect them.

Please help.

Edit: I tried to upload the attachment twice but an upload error occurred both times.

What happened was that when I tried to run the simulation, an error message said essentially: Don't recognise Vcc. I had wondered about specifying Vcc, but could not see how to do it.
 

Roff

Well-Known Member
ljcox said:
Ron,
In Melbourne, we don't have -2C even in winter. When I extracted myself from the garden, I fooled with SwCAD. Two questions:-

1. I inserted your model, but I can't see how to specify Vcc - see the screen dump below.
Notice in the screen capture above: ".param vcc=5". To place that on the schematic, click on the .op icon at the right end of the toolbar and type it in, then click OK. You need this tool for several options in SWCAD. I'm assuming you already know how to use it to add a component to the schematic that was not in the original library.


2. I read the help about mutual inductance, it said to use this format:- K1 L1 L2 1 but can't see how to input this data. I assume that L1 and L2 are drawn in the normal way and then the Mutual Inductance parameters are input to connect them.

Please help.
This is also done using .op. Type in "K1 L1 L2 0.999" (or whatever value you choose) and click OK.
Edit: I tried to upload the attachment twice but an upload error occurred both times.

What happened was that when I tried to run the simulation, an error message said essentially: Don't recognise Vcc. I had wondered about specifying Vcc, but could not see how to do it.
 

nicotrozzo

New Member
OK, place a Schmitt trigger on the schematic and right-click on it. Below is a screen capture of this. I parameterized the logic high voltage as an example. You could just make it 4, or 5, or whatever you think is right. I also picked typical values for delay, rise time, threshold voltage, and hysteresis. You can get them from the datasheet. If you want to add input and output resistance and capacitance, you will have to add them externally.
This model is only behavioral, but is still very useful, and runs very fast.
You can, of course, do similar setups with any of the digital parts. The D FF is very useful. I made a model of a 4-bit counter using these models,and it matched the CMOS part (can't remember which one, and I think it's on my computer at work) pretty well.
A few years later, this was useful for me too using LTSpcice, thank you!
 

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