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LTspice help needed

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Mikebits

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Hoping someone can help me out here. I have this sim file that runs slower than you know what. Can anyone tell me why this sim runs so slow?
 

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  • analogmux.asc
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hi Mike, Merry Xmas.

Trying to find why it runs so sloooow, let you know if I have any ideas.

Eric

EDIT:
The problem persists even with only the left side HC161 and SP clock source on the circuit.??

I will keep looking.
 
Last edited:
hi Mike,
I have changed the SPI clock timing, also added some cycles to the sine wave sources, changed the OPA type

It runs a lot faster, give it a try.
 

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  • analogmux_mike1.asc
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Thanks a million Eric, your the best :)
 
Mike, there is a super active Yahoo group that can help you I am sure. I joined that group, but most of it is way over my head. There is a German guy named Helmut that is the driving force behind it who is way smart on how to get it to do anything you want. Hope this helps.
Bob
 
Eric, where did you get the CA3140? I looked on yahoo LT-spice but could not find it.
 
Mike, if you trust U2, U4, and U5 to work as designed, why not replace sig1, sig2, and sig3 with voltage sources?
As Eric pointed out, zero rise and fall times are not a good idea.
 
Eric, where did you get the CA3140? I looked on yahoo LT-spice but could not find it.

hi Mike,
I would get the MCP6002 rail2rail OPA from the Yahoo LTspice user group web page.

The CA3140 is a modified model that I use for ~0Vout thru to Vdd-1.5Vout.... I tweak the models parameters as required to make it 'similar' to any device I am working on.

BTW: the MCP6002 dual costs only around 50p in the UK, so its a handy OPA to have on your work bench, it also comes in a quad version.

I would suggest that you dont use nanosec rise/clock times when using LTS.
I usually start off at 1uSec or 0.1uS.

Post your asc file and will run it.

Regards
 
Mike,

another tip: use the generic parametric opamp to get your circuit initially running. Substitute specific OpAmp models only after the basic circuit functions to your satisfaction...
 
Thanks for all the input :)
 
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