I am working on a design that uses a number of level shifters, whose height is unfortunately not a multiple of the standard cell height (level shifter height is 3.9µm whereas the standard cell height is 2.6µm).
In order to accomodate this, as per the recommendations in the NIMH section of the Floorplan design user manual, I have set up seperate power domains for all the different types of level shifters, containing only instances containing just level shifter cells, and create the rows within these power domains via the createRow command, specifying the new appropriate core SITE to use:
createRow -site CORE_LS -noFlip -noAbut -spacing 1.3 -powerDomain PD_LS1
This creates the correct rows, but unfortunately during the placeDesign (and refinePlace) steps, the level shifter cells are not placed within these rows, and in such a way that the followpins that are created do not line up properly with the power rail connections within the cells.
While it is possible to force correct alignment of these cells through the use of the snapFPlan and some scripting, violations are generated, and some domains have incomplete followpins.
Therefore could anyone give me some guidance as to how to align these level shifters properly within the rows of their respective power domains to avoid such problems?
Thank you for your time and trouble,Franchie.
Hello, and thanks for your help!
Because the level shifters are not multiples of a standard cell height, according to the Cadence documentation they must be placed in their own power domains. This was done, I believe, correctly, but still did not align them with the rows.
The tape-out has passed now, so I gave up trying to find a solution to this and instead concentrated on getting the cells in the right place through less elegant methods. I was able to get limited success by using the adjustPowerDomainToAlignRows command, which resized the various power domains in order to align their rows.
Thank you for your help in any case, it is really greatly appreciated!