I am truly a novice in PCB design, so I am new to all aspects of it. What I am having the most trouble with is actually picking suitable components. The trouble I am having is that I am not really able to use most of the components I find from Google or elsewhere.
To use a component on a board, I want to be able to stick it in some PCB design software and be able to use it in a schematic, place it on the PCB and simulate its behavior. However, this seems to be endlessly difficult. The problems I run in to are:
- I can't find the part in any component library anywhere
- I can't find a simulation (SPICE/IBIS) model for the part
- I find a SPICE model, but it is for some different version of SPICE and doesn't work
- I find the component in a library, and a simulation model, but it is an outdated component and not recommended for new designs
- Everything else is fine, but I can't find the SMD version of the component
The end result is that when going over Farnell component listings, I am forced to pick components based on what I can simulate and find in some library, instead of picking the component that is most suitable for the design. This seems like it should not be so.
Is there any way to actually have a large library of components for which all of these things exist? The best I have come across so far Eagle with component libraries for every manufacturer separately from Farnell community site. But even that is severely lacking as I don't usually find the components I want from the manufacturer in the library – and obviously there are no simulation models for these. Eagle also has the nice DesignLink feature, but that doesn't seem to help me any in this case.
As an example: I am looking for a generic opto-coupler with transistor output, 4 pin SMD package and 100% or more CTR. I'd like to be able to compare a few options and not pick the one option that might be available for both my simulation software and my PCB design software.
Commercial solutions are okay.
Best Answer
You will never find an absolutely complete parts library from any vendor. What you need to do is learn how to use the library editor of your tool. There you create packages and symbols that you can place in your schematic and layout, based on the datasheets from the manufacturer.
As far as simulation goes, there is no complete/unified tool for this. You'll really only find SPICE models for basic parts, such as transistors and diodes, and sometimes for bus drivers (like pins in an fpga). You'll use a SPICE simulator for doing timing and frequency analysis for that kind of thing. For code, you'll use the simulator that usually comes with the development environment of the processor. For VHDL/Verilog, you'll need a simulator such as ModelSim for that. And for simulating transmission lines for signal integrity, there are also separate simulators that take in geometric and materials data, and also the bus driver models I mentioned before.
So the idea of simulating the whole design in one go is not really feasible, unless its scope is very narrow. What you end up doing is simulating each subsystem separately in its own suitable testbech environment, and then join everything in the pcb. Once a prototype has been manufactured, you can test, probe and debug the system as a whole.