Noise injection and propagation in high performance designs

Signal integrity has become a critical issue in the design of high-performance circuits. Noise on a net arises both through propagation of noise from previous stages through the driver gate of the net and through injection of new noise through coupling capacitance with neighboring nets. Typically, propagated noise and injected noise are added linearly to simplify the analysis and increase its efficiency. In this paper, we show that this linear assumption results in a significant underestimation of the noise, due to the nonlinear behavior of the driver gate, and hence can lead to many undetected noise failures in the design. Since complete nonlinear simulation is too slow for large cell-based designs, we propose a new linear model that accurately captures the nonlinear behavior of the driver gate. We propose three iterative methods for computing the model parameters of this linear model. Results are presented to demonstrate the accuracy of the proposed approach on several industrial designs.