Camarillo, Calif—As clock rates increase in the quest to push more data from point A to B, maintaining signal integrity (SI) becomes more of a challenge. Designers are faced with a dilemma in how to solve the problem: slow the clock down; shorten cable and PC board interconnects; or go to more exotic substrates instead of the ubiquitous, relatively inexpensive FR4 material. Each of these alternatives have performance, design, and BOM cost implications.
There's one other tool in the kit: use equalization to improve the signal quality, despite these SI impediments. That's the goal of the Vitesse VSC7224, a multirate 14 Gbps quad adaptive channel extender, which takes impaired signal inputs and delivers retimed or redriven outputs for signals between 155 Mbps to 14 Gbps; each channel can operate at a different rate.
Using this IC, designers should be able to drive up to 65 inches (165 cm) of FR4 trace or 20 meters of 24 AWG twin-axial copper cable, as the device also yields an isolation-to-crosstalk ratio (TCR) of at least 12 dB. Target applications include 10G/40G/100G Ethernet, Infiniband FDR, and 16G Fibre Channel designs.
The adaptive receiver, with its four-tap decision feedback equalizer (DFE), can be set-up via a pin-strap or an I2C interface (pin-strapping reduces system complexity and processor-interface chores). The device also provides monitoring for the all-important eye diagram, which shows so many aspects of the signal fidelity and SI situation, as the VSC7224 includes Vitesse's Vscope embedded waveform-viewing function.
The CMOS IC is also power efficient. Users can select either redriver mode (100 mW/channel) or retimer mode (180 mW/channel), to trade power and application priorities; the IC uses a 25 MHz crystal for clock/data recovery functions.
Packaging and availability: The VSC7224 is housed in a 5×9 mm QFN package, and is sampling now. It is built using a standard CMOS process.
For more information, go to http://www.vitesse.com/products/product.php?number=VSC7224 .