Introduction to Delay Models
• CCS stands for Composit Current Sourse Model, and NLDM stands for Non-Linear Delay Model.
• Both CCS & NLDM are delay models used in timing analyze.
Key Differences in Driver Modeling
• NLDM uses a voltage source for driver modeling
• CCS uses a current source for driver modeling
Advantages of CCS over NLDM
• The issues with NLDM modeling is that, when the drive resistance RD becomes much less than Znet(network load impedance), then ideal condition arises i.e Vout=Vin.
• Which is impossible in practical conditions.
• So with NLDM modeling parameters like the cell delay calculation, skew calculation will be inaccurate.
• That is the reason why we prefer CCS to NLDM
