ADDRESSING SUBSTRATE COUPLING IN MIXED-MODE ICS - SIMULATION AND POWER DISTRIBUTION SYNTHESIS

This paper describes new techniques for the simulation and power distr ibution synthesis of mixed analog/digital integrated circuits consider ing the parasitic coupling of noise through the common substrate. By s patially discretizing a simplified form of Maxwell's equations, a thre e-dimensional linear mesh model of the substrate is developed. For sim ulation, a macromodel of the fine substrate mesh is formulated and a m odified version of SPICE3 is used to simulate the electrical circuit c oupled with the macromodel. For synthesis, a coarse substrate mesh, an d interconnect models are used to couple linear macromodels of circuit functional blocks. Asymptotic Waveform Evaluation (AWE) is used to ev aluate the electrical behavior of the network at every iteration in th e synthesis process. Macromodel simulations are significantly faster t han device level simulations and compare accurately to measured result s. Synthesis results demonstrate the critical need to constrain substr ate noise and simultaneously optimize power bus geometry and pad assig nment to meet performance targets.