Design / Library Management

dick_freebird

I'm starting to accumulate and now reuse a lot of low
level (custom transistor) layouts in my work and it's
getting a bit crowded in the file pile.

I have seen that there's some kind of "use a second
GDS file as a library" capacity. I've found it a bit clunky
to copy between open layouts so have been just exporting
"done" devices to their own individual GDS file. Those
seem like my two options for corralling a herd of funky
one-off device layouts for a series of future products
(a lateral PNP is a lateral PNP, unless it's in a LM158).

But thought I'd kick off a discussion of how other people
(if anybody out there is going down the same or similar
road) like to approach this aspect of design management.

Matthias

Basically libraries are a simple way to organize layouts.

There is a simple way to use GDS files as libraries:

1. Put everything you want to see as a library element into it's own top cell
2. Save the GDS file with a meaningful LIBNAME (see GDS writer options)
3. Put the GDS file into the ~/.klayout/libraries folder (you can also stash it somewhere else and use $KLAYOUT_PATH to define multiple places KLayout looks for). On Windows the place is c:\Users\you\KLayout\libraries.

You will then find the new library under the LIBNAME you gave it when saving in the library browser (by default below the cell list).

Some things are worth noting:

1. The Layer numbers are not translated so they need to fit to your technology. It's possible to define technologies and assign libraries to them if needed. In that case a library becomes visible only if that technology is selected.
2. Database units should be translated, but I'd recommend using the same DBU across libraries and layouts which use them.
3. Library cells can contain PCells and cells from other libraries. In that case these other libraries need to be available too.
4. If a layout uses Library cells, these instances are annotated in a special way in GDS (like PCells). If you load such a file with a different KLayout where the library is not available, the cell will still be available content-wise, but it will be shown as combing from a "" library.
5. If you want to get rid of the library references (e.g. on tapeout), save the GDS file without "Cell context":

Matthias