Analogix Semiconductor has introduced a new family of physical-layer transceiver ICs that lets system designers replace fiber optics with less-expensive copper media in system-to-system interconnects, yet still achieve the high performance associated with fiber.

Analogix's new D-PHY xGC family of physical-layer transceiver (PHY) chips includes the first device to deliver 6.25 Gbps raw serial performance per copper twisted pair. With an aggregate capacity of 25 Gbps full-duplex over a single InfiniBand copper cable at up to 30 meters, it offers twice the speed and distance of today's standard 10GBASE-CX4 chips.

This D-PHY 5GC device is also the first high-speed transceiver to operate over unshielded twisted pair, providing a less costly alternative to InfiniBand cable at a time when a high-speed UTP-based standard could be up to two years away. It offers designers major advantages in high-speed, short-distance interconnect scenarios, such as stackable switches or cross-rack clusters, where costly fiber was previously the only choice.

The D-PHY 5GC and a standards-based counterpart, the D-PHY 2.5GC, are already sampling to customers. The D-PHY 2.5GC, designed for customers connecting heterogeneous multi-vendor systems over copper media, is fully compliant with the 10GBASE-CX4 standard, offering 4X3.25-Gbps performance. However, it operates over distances of up to 40 meters--nearly triple the 15-meter specification of the standard.

A second generation of the D-PHY xGC devices, offering serial speed of up to 12.5Gbps and aggregate capacity of 50Gbps over InfiniBand cable and 25Gbps over UTP, will be available in 2005. Like the 5-Gigabit devices being introduced, the two upcoming 10-Gigabit D-PHY xGC devices will include both a standards-based version (the emerging IEEE 10GBASE-T standard) and a proprietary version offering higher speed and media flexibility.

Advanced equalization and low-jitter transmission address high-speed issues

Sending high-speed signals over copper cable, particularly unshielded cable, poses special challenges: high levels of crosstalk, impedance discontinuities at the cable/connector interface, and electromagnetic interference (EMI) that occurs at high frequencies. The D-PHY xGC family addresses these challenges through a combination of advanced technologies on both the receive and transmit sides. Two-stage, active linear equalization on the receiver, with low power and die-area requirements, provides an appropriate high-frequency signal boost without introducing new noise effects or aggravating existing ones. The highly sensitive receiver can recover signals from Analogix's very low-jitter transmitter, which uses minimal pre-emphasis and a low output swing to increase crosstalk immunity and address other noise issues. The D-PHY xGC family also meets FCC Part 15 Class A EMI specifications.