Handling of mutual inductance in simulation of simultaneous switching noise

Accuracy of a circuit simulation for the simultaneous switching noise associated with a conventional plastic package was significantly improved by taking into account mutual inductances among leads. The effective inductance of a lead on a plastic package was suspected to be influenced by many other leads in the package. We have thus formulated a three dimensional conductor model for bonding wires, leads, and socket conductors to take into account their three dimensional structure. We calculated the mutual inductances and simulated the simultaneous switching noise by either including elements in the mutual inductance matrix or not. We clarified the contribution by the elements in the matrix, and a modeling technique for accurately simulating the simultaneous switching noise was proposed. This technique was developed for predicting characteristics of a assembled high-speed and multiple-bit device accurately during the circuit design stage. This would allow us to tailor the output circuit for maximum performance of devices under assembled condition. The design of the output circuit affects the simultaneous switching noise through the effective inductance of the ground line