spice simulation usefull or not 7

[2dye4]

I was just reading in previos thread about good tools
to have on the electronics bench and once again I hear
of the evils of Spice circuit simulation.
What problems do people really have with spice or what
situations can cause it to give incorrect results.
Please confine your answears to those cases where the
circuit is reasonable well modeled by the components.
We all know about Garbage in Garbage out.
I ask because I use it frequently and rarely has it lied
to me.
In those cases the integration time step was not correctly
reduced and the circuit solution was in error.
My standard procedure now is to force a small time step
simulate then force a 0.8 X timestep and simulate.
Then compare the results. If agreement call it done.
It has not lied to me since I began this procedure.

thnks

 

[cbarn24050]

Or a better design. I see the old calculator example has come up. Snag there is a calculator was made to be friendly to the user, spice isn't.

 

[OutToLunch]

I can't speak for all datasheets - you're right, there are some poor ones out there. I can speak about the datasheets that I write - I do my best to describe how every feature works and how to implement those features properly. Regarding the spec tables - there are gives and takes. We need to supply all the pertinent specifications that we can on the spec tables. Anything you see on the spec table is a tested parameter and is guaranteed throughout the operating temperature range of the IC. If we can't test a particular parameter, but it is important to the design, then we will put something like "Guaranteed By Design" or something similar on the table or include it in the functional description. If you want every single testable parameter to be tested and listed on the spec table, then be prepared to pay more money for the part because each part does get tested and it takes time to test each part - and of course time is money.

And why does, "It is invaluable to find out just what is happening inside the IC" not apply to the system designer?

I was speaking in terms of responding to a problem or a failure that a customer may be experiencing. Typically, problems like this are a small percentage of the total amount of parts being used - usually the problem is specific to the application in question. We need to get to a root cause, and simulation by the designer may be required.

Have you ever tried to contact the applications support of the company that mfg's the IC your using to help with any issues you are having? Some companies are better than others when it comes to that, but you should be able to get some type of response about how the part should behave in a given application.