oLibrary Characterization: The cell library (.lib file) specifies a maximum transition time for which the cell delays are accurately characterized. Exceeding this can lead to inaccurate timing analysis. Your max_transition value must be within this characterized range.
- Very tight transition target can cause more latency, unnecessary buf/inv insertion.
- Thumb Rule: A common practice is to set the clock transition target to be about 10-15% of the clock period as a starting point, then tighten or loosen it based on power and performance requirements.