Glossary comparison
LEF vs Liberty: what is the difference?
The difference
A Liberty file models a cell's timing, power, noise and test behaviour. LEF describes its physical shape. Place and route tools need both.
LEF describes a cell's physical abstract, such as its size, pins and blockages, for place and route. Liberty describes its electrical behaviour for synthesis and timing.
The two terms
LEF
An ASCII format describing the physical abstract of library cells and macros: outline, pin shapes and layers, obstructions and antenna data. Place and route tools read LEF instead of full GDSII geometry to keep the design database tractable.
Liberty
The standard ASCII format for describing a cell library's timing, power, noise and functional behaviour to synthesis and timing tools. Each .lib file covers one PVT corner and holds per-arc delay and transition data plus pin capacitances and constraints.
Side by side
| Field | LEF | Liberty |
|---|---|---|
| Stands for | Library Exchange Format | Not an abbreviation |
| Type | Standard | Standard |
| Domain | EDA Tools & Flows | EDA Tools & Flows |
| Group | Design data formats | PDK and libraries |