Quad-packs in LTSpice schematics?

Its amazing what people will try and get for free. You want fries with that as well?

Kevin Aylward snipped-for-privacy@anasoft.co.uk

SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design.

I think it wouldn't be too hard to use LTSpice as the schematic capture for a PCB layout with multiple parts per package. You would have to to write a little bit of code to deal with the resulting netlist. LTSpice allows just about any text in a reference designator.

You can call one part "U1A" and the next "U1B" and so on. Then a bit of software could strip off the "A", "B" and etc and adjust the pin numbers in the saved netlist. Texts could be used to hold the attributes of the traces, so you can even include traces width and clearance values.

I think that this is a very worthy project.

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kensmith@rahul.net   forging knowledge

Hi Ken,

Yes, it certainly would be but I am not much of a programmer. But I'll probably experiment a little and when I figure something out I will post about that.

Regards, Joerg

Hi Kevin,

Yes, garlic fries. And heavy on the dill, please.

This is not about getting a freebie. I do have properly purchased schematic editing and simulation available but it requires finishing the schematic and export part of it, generate the list, check that the list is ok, then feed it into Spice and simulate. Works nicely for me. No need to buy yet another product.

What I am looking for is something that skips the listing requirement and also avoids having to draw parts of the circuit twice. LTSpice has the advantage that I could ask clients to obtain it and then see for themselves what the change of certain parameters does. Often there are younger engineers who can benefit from that and gain more understanding of how things work. Since they don't have to file a cap ex request and wait for approval that would be a straightforward process with a free product such as LTSpice. From what I have seen so far LTSpice is a very decent product and since my designs often contain PWM voltage conversion it is even more suitable. In case an LT device is used, they've got almost all their products in there.

Regards, Joerg

If you do a good job of documenting what needs to be done, you will be 90% of the way towards the software needed. Getting someone to turn a good discription into software shouldn't be too hard. Just don't ask for a GUI.

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kensmith@rahul.net   forging knowledge

I agree that it would be wonderful to have a one really good tool that does simulation and pcb all in the one go. However, invariably, PCB guys like different things in the schematic capture than simulation guys do, so the captures end up being different. In my view, you will never please both the pcb and design people in the one system, in this universe anyway.

Kevin Aylward snipped-for-privacy@anasoft.co.uk

SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design.

Hi Kevin,

That's right. Although there ought to be a reasonable compromise somewhere that avoids having to key in schematics twice. Most projects, at least here on the US west coast work like this: Engineer designs, simulates, tests and draws schematic. Then it is handed to the client or boss for design review plus another review in a group. Afterwards a netlist is compiled, checked and then sent off to the layout folks. The layout is almost always farmed out and the layouter doesn't really care about the schematic. He or she just wants a netlist and package sizes, plus some guidance for critical stuff.

Regards, Joerg

Not totally true anymore with highspeed designs [on the West Coast].

Quite often a schematic will contain constraints for lengths etc of traces. The Engineer will place the contraints in the design, the PCB guy will lay it out and then the Enginner/Signal Integrity guy will simulate using back annotated PCB lengths/stubs.

The process is becoming more tightly coupled [and iterative] due to the faster edge rates and clock speeds. Jitter is also becoming very important so that margins have to be carefully watched.

Hi crzndog,

Yes, there are lots of critical layout. I had quite a few of those, too. However, I always made sure that the layouter is experienced in this stuff, knows why I don't want 90 degree bends and so on, and is local. Or at least within reasonable driving distance. In Europe or Asia that matters less because you can often hop on a fast train and in an hour you are more than 100 miles down the 'road'.

Then I sit down with the layouter and a cup of coffee to hash out the critical areas. This has worked well for really tricky RF designs. The only problems I ever had were minimal. Once a layouter smoked a bit too much. If it were pipe instead of cigarettes I wouldn't have minded. Another had a cat and its sensitive nose didn't appreciate the fact that we have dogs at home. When I came back from that one our dogs gave me 'the looks'.

Regards, Joerg