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Jan 12

Orcad Copy Schematic Symbol

There are a ton of pre-drawn components in the PSpice library. I’d rather use one of these as a starting point for my design instead of having to create my own from scratch. This post details how to copy an existing symbol and attach an external Pspice Model.


Open Orcad Capture and create a new library. Save it as something intuitive.
File-> New Library

Open the library with the symbol you want to copy. I’m going to use the FDC6322CP Symbol from my Fairchild library file.

Right Click->Copy the symbol.

Right Click->Past on your library.
Right Click->Rename the part.
Right Click->Edit part

Options->Package Properties
Change Reference to Q
Change PCB footprint to FDN340P.


Orcad should be able to locate your footprint if you enter it’s name in “PCB Footprint.” If not, you may have to add your directory in the capture.ini file.

Locate (Install Directory)\tools\capture\capture.ini

There should be a section similar to this in the file.  If not, add what is necessary.

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[Footprint Viewer Type]
Type=Allegro
[Allegro Footprints]
Dir0=Footprint Directory
Dir1=Secondary Footprint Directory.
Dir2=Third....etc

Finally change the part name and your symbol is set up.

 

Attaching a Model:

Fairchild provided a .mod file for the FDN340P while Orcad is looking for a .lib file. After opening the original parts pspice text as well as the new .mod file I determined that they were both in the same format. Renaming the .mod to .lib should allow me to associate the new model.

One problem with the new model is an extra pin which seems to be some type of internal temperature monitor. Since our symbol only has three pins we will not be able to associate the two. Unfortunately, I don’t yet know enough about the Spice model language to fix this so I am just going to add a temperature pin to the model.  Things seem to get a little messy with pin placement so you may have to switch snap to grid off and do some manual alignment of the symbol.

While you’re at it you can right click the symbol and view footprint to verify that the symbol and footprint are correct. In this case the pins are numbered wrong on the symbol which is causing them to be mapped incorrectly.

After renumbering the pins your footprint should match the datasheet, as shown below.

Close your active windows until you are back to your library window. Right Click and choose “Associate PSpice Model” to attach your downloaded model.  Browse for the renamed .lib file and a matching model should show up in the window. 

 

Finally, configure the pins as defined in the model comments. Click finish and the model is complete.  After saving this symbol can be used in capture schematics, both for simulation and PCB layout.


Sources:

Footprint

Datasheet

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