Staggered Twisted-Bundle Interconnect for Crosstalk and Delay Reduction

Abstract

To achieve small delay and low crosstalk for multiple signal nets with capacitive and inductive coupling, we propose in this paper a novel interconnect structure, staggered twisted-bundle wires, where groups of twisted wires are staggered. This new structure is different from the previously proposed twisted bundle wires with one group of twisted wires and another group of normal wires. Using accurate circuit models and efficient algorithms to find the worst case noise and delay for comprehensive combinations of signal patterns and a range or arrival times, we assume signal and shielding ratio over 1:1 for area reduction and compare the aforementioned two structures to coplanar shielding for signal nets. The staggered twisted-bundle has the smallest worst case delay, up to 20% and 5% smaller than the coplanar shielding and twisted bundle, respectively. The staggered twisted bundle also has the smallest worst case noise, up to 6% and 12% less than coplanar shielding and twisted bundle. Furthermore, the staggered twisted bundle has the smallest delay/noise variation between signal nets. We conclude that without increasing routing area, the staggered twisted bundle is better than the twisted bundle and coplanar shielding in terms of performance and noise.