[DRC] Fanout & Capacitance Constraints - why both are needed?

[ivlsi]

Hi All,

As for DRC, why both Fanout & Capacitance Constraints are needed? Isn't enough have just one of them?

Thank you!

 

[rca]

Capacitance is required to respect liberty timing.
Fanout is not mandatory to be respected as timing but it could be needed as company rule, like tie cell.

 

[ivlsi]

sure rca! the max fanout also make a limit for the current driven into output stage of the driving cell (IMHO)