Ground-referenced signaling for intra-chip and short-reach chip-to-chip interconnects
Walker J. Turner, John W. Poulton, John Wilson, Xi Chen, Stephen G. Tell, Matthew R. Fojtik, Thomas H. Greer, Brian Zimmer, Sanquan Song, Nikola M. Nedovic, Sudhir S. Kudva, Sunil R. Sudhakaran, Rizwan Bashirullah, Wenxu Zhao, William J. Dally, C. Thomas Gray · 2018
While high-speed single-ended signaling maximizes pin and wire utilization within on- and off-chip serial links, problems associated with conventional signaling methods result in energy inefficiencies. Ground-referenced signaling (GRS) solves many of the problems of single-ended signaling systems and can be adapted for signaling across RC-dominated channels and LC transmission lines. The combination of GRS and clock forwarding enables simple but efficient signaling across on-chip communication fabrics, off-chip organic packages, and off-package printed circuit boards. Various methodologies compatible with GRS are presented in this paper, including design considerations and various circuit architectures. Experimental results for multiple generations of GRS-based serial links are presented, which includes a 16Gb/s 170fJ/b/mm on-chip link, a 20Gb/s 0.58pJ/b link across an organic package, and a 25Gb/s 1.17pJ/b link signaling over a printed-circuit board.