LVF is an extension to the Liberty format that adds statistical variation information to timing measurements. The Liberty Variation Format (LVF) introduces a local standard deviation sigma into the cell characterization library data, and a table format for. Timing signoff tools, with the increased variation modeling fidelity of the SOCV/ LVF model, use an SSTA engine to propagate statistical arrival time. VLSI characterization timing variation model. At yet smaller process nodes, such as 20/22nm and below, OCV is modelled using the Liberty Variation Format (LVF).