SAN MATEO, Calif. Broadcom Corp. is sampling a four-port Gigabit Ethernet transceiver for switches and routers that integrates a delay-locked loop. The extra circuitry means designers won't have to worry about adding delay traces when using a newer, low-pin-count interface between a design's physical-layer and media-access control devices.
The BCM5424 transceiver includes the Reduced Gigabit Media Independent Interface (RGMII), an open industry-standard interface that cuts the number of signal paths from the 25 needed for standard GMII down to12. But though RGMII requires fewer pins, it needs a long timing-delay trace that takes up valuable board real estate.
"The problem with the RGMII spec is it allowed for a skew in the timing between the switched MAC ASIC and the PHY," said Jim Muth, product manager at Broadcom (Irvine, Calif.). "You have to accommodate for that with a 6-inch trace on the board. There is one for transmit and one for receive, so if you're doing a 48-port board all that reduced pin count is counteracted by the fact that you have long traces required."
These traces are usually arranged in a spiral on the board, taking up approximately 1 square inch of board space per trace. A 48-port board, for example, would require 96 square inches of layout space.
With the 5424, designers can do without these islands of coiled traces thanks to an integrated DLL that locks onto the signal coming from the MAC and "then provides the delay before the signal is actually processed," Muth said.
Based on a digital signal-processing engine that can deliver 1 trillion operations per second, the transceiver is capable of 10-, 100- and 1,000-Mbit/second Ethernet speeds. It is compatible with all existing network equipment operating over legacy Category 5 copper cable plants, Broadcom said, and can automatically negotiate to maximum speed over an impaired cable plant regardless of the maximum speed specified by the end equipment.
Broadcom is selling samples to select customers for $90 apiece in quantities of 1,000. The device is expected to ship in high volume by year's end, and will be manufactured in a 0.13-micron process at Taiwan Semiconductor Manufacturing Co.