I mentioned this already, but I think it is worth a bit more elaboration.??John Woodgate wrote:
... but it is a problem when passing data to a PC layout app.
SPICE/LTspice simulations are never meant to constitute the full and complete design database for a circuit layout.? Yes, you can take a schematic in LTspice and export it to a file that can be read by a PC layout program, and that's fine.? But you should ALWAYS assume that the LTspice-generated netlist does not have some things that are necessary for the physical layout, because they were not needed to simulate the circuit.? It should ALWAYS be assumed that modifications and touch-ups will be needed, after the circuit is ported into a PCB layout system.? Anyone who takes an LTspice simulation, exports it to a layout program, and blindly uses it that way is "shooting themselves in the foot".
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The SPICE models for many ICs are not 100% complete and do not include some physical pins.? Some LTspice models omit pins and the functions that connect to those pins, because almost no design engineer ever needs to simulate those parts of the circuit.? So they are omitted from the LTspice model and from the LTspice simulation.? But the real IC has them, and you may need to do something with those pins in the physical design even though they were not a part of the simulation.
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