As a result, manufacturers are starting to shift from single-ended to higher-speed differential-pair signaling in backplane systems and have produced several new high-speed, differential backplane connector families in the process. Among them are Erni/Tyco's ERmet ZD connector, FCI's Metral connector line, Fujitsu's MicroGiGaCN connector series, the Molex/Teradyne VHDM-HSD products and Tyco's MultiGig signal modules.

The journey hasn't been an easy one, though. Connector suppliers have had to figure out how to provide the highest performance possible in data rate transmissions and signal integrity without sacrificing electrical parameters governing capacitance, crosstalk, impedance, inductance and reflection. These connector companies have found that they also need to evaluate RF characteristics, such as insertion and return losses, more carefully at higher data rates.

Some significant problem areas connector manufacturers are addressing include pc-board routing and the use and size of the vias, which contribute to signal integrity problems. While many connector companies still prefer to design with traditional press-fit technology and FR-4 materials, some are shifting to surface-mount technology (SMT) as a way to boost performance.

Vendors are also beginning to examine and test the entire interconnect, not just the connector itself, in speedy environments. A high-speed connector may meet testing requirements at higher data rates-which is the way many electrical engineers test-but that same connector may not be able to handle the same speed when terminated to a cable or placed on a pcb. This shift in thinking is causing some confusion among suppliers and buyers alike.

Connector makers are managing the problem by calculating the effects of a pc board on signal strength into the final modeling and testing of a new connector design. "We want to see what the signal looks like as the signal goes down the pc board, as it comes into the connector, transverses the connector and exits through to a cable or a board on the other side," said Jim McGrath, director of strategic products at Molex Inc. (Lisle, Ill.). "If there is a 100-ohm spec, plus/minus 10 percent, we have to meet that specification on the entire interconnect, not just through the connector. In a high-speed environment you cannot look at individual components, you have to look at the entire system. One component does have an effect on an adjacent component. That's the key to high-speed design."

In a year when winning volume orders was the exception, not the rule, major connector manufacturers have used the downtime to develop high-speed connectors that meet next-generation transmission speeds up to 10 Gbits/s. Several companies-Tyco Electronics, Erni Components Inc. and Teradyne Connection Systems Division among them-already have something to show for their efforts.

New to the market is Tyco Electronics' modular MultiGig RT family of high-speed board-to-board connectors that offer scalability from less than 1 Gbit/s to 10 Gbits/s and beyond. The connectors provide design flexibility in both signal-contact density and card-slot pitch. They replace conventional pins with a miniature pcb structure on the daughtercard modules and provide fully enclosed dual-beam contacts on the backplane connector. Tyco uses press-fit pin technology for all high-speed signal contacts.

Tyco's goal was to optimize impedance, noise and insertion loss, yet still supply a product that gives customers the density they want, said David Helster, director of circuits and design at Tyco Electronics (Harrisburg, Pa.). His group focuses on signal integrity and high-speed analysis.

Helster said the MultiGig RT system minimizes electrical skew by controlling the length of each circuit through the connector. Available in single-ended and differential applications, the MultiGig-1 signal modules are designed to meet data rate performance beyond 3 Gbits/s and provide a signal density of 140 contacts per inch. They are available in 0.8-inch and 1-inch pitch card spacing.

The MultiGig-2 signal modules offer high-speed density of 113 contacts/inch and meet data rate performance between 3 and 6 Gbits/s. Supporting high-speed data transfers beyond 10 Gbits/s, the MultiGig RT-3's density allows 63 contacts/inch.

Tyco also is also selling a new suite of high-speed board-to-board and I/O connectors for Xaui, the emerging universal interface developed by the 10-Gbit/s Ethernet Task Force. The low-pin-count Xaui electrical interface comprises four differential channels, each operating at 3.125 Gbits/s, for an aggregate bandwidth of 12.5 or 10 Gbits/s. Product features include low noise, matched impedance and multigigabit performance, and each of the the new Tyco products supports serial speeds up to and greater than 3.125 Gbits/s, the company said.

The Tyco product suite encompasses Z-Pack HM-ZD connectors, ZFP I/O connectors, SFP press-fit cage systems, PT connectors and Champ Z-DOK connectors. The Z-Pack HM-ZD, a high-performance backplane interconnect system, uses a board footprint that aligns the ground and signal pins in a 1.5 x 2.5-mm grid, mooting the need for staggered routing between adjacent columns. Designed for data rates of 6.25-Gbits/s, the Champ Z-DOK connectors use standard FR-4 board materials and routing techniques. The system features a TRI-Q differential-pair contact system that maximizes data throughput and minimizes pair-to-pair crosstalk and impedance discontinuities, according to the company.

VITA, PICMG specs

A dual-source differential board-to-backplane connector called the Erni-Tyco ZD connector was chosen as the high-speed data-transport connector to support both the VME International Trade Association's VITA-34 switched-fabric architecture and Advanced TCA, the PICMG Group's Advanced Telecom Architecture for next-generation communications equipment.

Also coming to market with new offerings is Erni Components Inc., which recently launched a differential connector system called the ERmet zeroXT that is intended for data rates up to 10 Gbits/s. The enhanced ERmet ZD connector offers an innovative shielding design, improved crosstalk performance and SMT termination for data rates up to 10 Gbits/ s. The company's move from a traditional press-fit approach to surface-mount technology for backplane connectors is helping to convince the industry the SMT versions can withstand the physical abuse that a typical backplane connector takes, said Michael Munroe, director of marketing at Erni (Chester, Va.). "A good deal of work needs to be done to prepare customers and manufacturing processes to accept the XT surface-mount versions," he said. Down the line, Erni will develop press-fit versions of the XT and surface-mount versions of the ZD connectors, Munroe said.

The ZD connectors use an optimized grid design with a wafer pitch of 2.5 mm. An inline design of signal and ground pins makes trace routing easier. And the wider 2.5-mm pitch, wafer to wafer, translates into wider traces and clearances to reduce noise and improve signal integrity above 1 and 2 Gbits/s, Munroe said.

Erni uses microvia technology and SMT in the signal path, to provide better reflection than press-fit technol-ogy. Initially available in four pairs and module lengths of 25 and 50 mm, each 100- ohms differential pair of the ERmet zeroXT is a transmission line.

The connectors are available in SMT or through-hole terminations.

The ERmet zeroXT's pin density and layout are compatible with the ERmet ZD, which means it can accommodate system upgrades to higher frequencies without the need to change pc-board layouts, the company said. However, pcb materials and the back-drill of the pc-board holes will have to be taken into consideration.

10-Gbit Ethernet

Earlier this year, Teradyne Connections Systems Division (Nashua, N.H.) introduced its GbX platform connector for 10-Gbit/s Ethernet applications with less than 2 percent crosstalk. Offering four high-speed pairs per wafer, easy routing, a reduced-capacitance via structure and low crosstalk, the GbX can be used for 10-Gbit/s (4 x 3.125-Gbit/s) Xaui data rates. The four-pair platform provides 55 differential pairs per linear inch, and the five-pair configuration offers 60 differential pairs per linear inch. With a twin-axial structure in the mating area, the GbX platform offers additional shielding and better crosstalk control at fast rise times, the company said.

At Supercomm 2002, Vitesse Semiconductor Corp. demonstrated a reference platform for high-capacity metro and core networking up to 640 Gbits/s. It uses Vitesse's TeraStream Intelligent Switch Fabric, and Teradyne's GbX connectors and high-speed back-plane. The working chassis includes the backplane, interconnect, power, thermal and chassis. The companies said the connector delivers data rates above 6.5 Gbits/s in a real-world environment across conventional backplanes.

Teradyne also is offering a high-speed differential VHDM M-HSD (multisourced with Molex) that is said to meet system speeds of up to 5 Gbits/s. The connectors deliver data rates of up to 2.5 Gbits/s.

Incorporating new packaging and contact geometry techniques, FCI Communications' Data and Consumer Division (Etters, Pa.) has expanded its high-speed 2-mm Metral connector family and improved the electrical characteristics of its high-performance family of interconnects. The Metral 4000 headers and receptacles use a new press-fit tail designed for 0.6-mm drilled holes to provide additional width for trace routing and lower capacitance of via holes, FCI said. Optimized for 100- ohms differential pairs, the receptacle is said to exhibit better impedance match and lower insertion loss.

FCI is also offering the back-panel connector in a BGA mount instead of press-fit, said Brian Stephenson, global marketing director for backplane connectors at FCI. Using BGA technology to attach a back-panel connector means vias are used only for electrical connection of the single layers within the board, not the connector. Thus, the vias can be made as small in diameter as the pc-board thickness allows. They can also be used with emerging technologies such as blind and buried microvias to significantly reduce loss, said the company. Samples are available for the Metral 8 x 5 connectors (40 differential pairs).

Infiniband's choice

Fujitsu Components America Inc. (Sunnyvale, Calif.) said its MicroGiGaCN high-density differential connector technology is well suited for moving into the 5- and 10-Gbit/s arena for copper. Currently, Fujitsu is working on making some slight modifications to the design that will enable better routing on the pc board and adapt to a much higher range of data rates. Already selected as the standard I/O connector by the Infiniband Trade Association, Fujitsu's MicroGiGaCN connector was recently picked as the standard interface for the 10-Gbit/s Fibre Channel copper link and by the Serial Attached SCSI Working Group. Other standards bodies are also reportedly evaluating the connector.

Yet another company working on high-speed designs is Samtec Inc. (New Albany, Ind.). Its QTS family of high-speed differential-pair and edge-mount terminal strips comes in a right-angle design that places a ground plane between the signal rows to maximize signal integrity. The company has tested the connector up to 10 Gbits/s and found that the performance is good up to 5 to 7 Gbits/s for the differential-pair version. Samtec also recently introduced the HFEM data-link series that terminates with single-ended (up to 120 I/Os) and differential-pair (up to 42 I/Os) high-speed connectors. They are available in 5- or 10-inch cable lengths. Customization is available.

Company Contacts

Erni Components Inc.
(804) 530-5012
www.erni.com

FCI Communications
Data and Consumer Division
(800) 237-2374
www.fciconnect.com

Fujitsu Components America Inc.
(800) 380-0059
www.fcai.fujitsu.com

Molex Inc.
(630) 969-4550
www.molex.com

Samtec Inc.
(812) 944-6733
www.samtec.com

Teradyne Connection Systems, a division of Teradyne Inc.
(603) 879-3600
www.teradyne.com/tcs

Tyco Electronics, a unit of Tyco International Inc.
(800) 522-6752
www.tycoelectronics.com

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