High-speed electrical signaling: overview and limitations

Advances in IC fabrication technology, coupled with aggressive circuit design, have led to exponential growth of IC speed and integration levels. For these improvements to benefit overall system performance, the communication bandwidth between systems and ICs must scale accordingly. Currently, communication links in various applications approach Gbps data rates. These applications include computer-to-peripheral connections, local area networks, memory buses, and multiprocessor interconnection networks. Designers are concerned that these links will soon reach the fundamental limits of electrical signaling. In this article, we examine the limitations of CMOS implementations of highspeed links and show that the links' performance should continue to scale with technology. To handle the interconnects' finite bandwidth, however requires more sophisticated signaling methods. CMOS circuits, typically slower than circuits implemented in nonmainstream technologies, are particularly attractive for common applications because of their lower cost. The overall system cost is further reduced when signaling components are implemented as macro cells, integrated on the same die with a microprocessor or signal processing block.