CLOSED FORM MODELING OF CROSSTALK FOR DISTRIBUTED RLCG ON-CHIP INTERCONNECTS USING DIFFERENCE MODEL APPROACH

On chip interconnect plays a dominant role on the circuit performance in both analog and digital domains. Interconnects can no longer be treated as mere delays or lumped RC networks. Crosstalk, ringing and reflections are just some of the issues that need to be addressed for the efficient design of high speed VLSI circuits. In order to accurately model these high frequency effects, inductance had been taken into consideration. Within this frequency range, the most accurate simulation model for on-chip VLSI interconnects was the distributed RLC model. Unfortunately, this model has many limitations at much higher of operating frequency used in today’s VLSI design. This can lead to inaccurate simulations if not modeled properly. At even higher frequency the conductance metrics has become a dominant factor and has to be taken into consideration for accurate modeling of the different on-chip performance parameters. The traditional analysis of crosstalk in a transmission line begins with a lossless LC representation, yielding a wave equation governing the system response. With the increase in frequency and interconnection length due to the increase in the number of on-chip devices, the lossy components are prevailing than the lossless components. With the reduction of pitch between the adjacent wires in deep sub-micron technologies, coupling capacitances are becoming significant. This increase in capacitances results the introduction of noise which is capable of propagating a logical fault. An inaccurate estimation of the crosstalk could be the origin of the malfunction of the circuit. Cross talk can be analyzed by computing the signal linkage between aggressor and victim nets. The aggressor net carries a signal that couples to the victim net through the parasitic capacitances [13]. To determine the effects that this cross talk will have on circuit operation, the resulting delays and logic levels for the victim nets must be computed. This paper proposes a difference model approach to derive crosstalk in the transform domain. A closed form solution for crosstalk is obtained by incorporating initial conditions using difference model approach for distributed RLCG interconnects. We have proposed an explicit expression for the estimation of cross-talk noise. Our model considers both lossless components (i.e. L, C) and lossy components (i.e. R, G). The SPICE simulation justifies the accuracy of our proposed approach.