SFP chipset supports 4-Gbit/sec Fibre Channel

August 20, 2004 Camarillo, CA -- Vitesse Semiconductor Corp. announced the availability of what it calls the first chipset designed for next-generation, multirate Fibre Channel and Gigabit Ethernet SFP modules. The SFP chipset offers rate selection capabilities for 1, 2, and 4 Gbits/sec.

August 20, 2004 Camarillo, CA -- Vitesse Semiconductor Corp. announced the availability of what it calls the first chipset designed for next-generation, multirate Fibre Channel and Gigabit Ethernet SFP modules. The SFP chipset offers rate selection capabilities for 1, 2, and 4 Gbits/sec.

The two-chip set reduces module chip count when compared with current market offerings and provides enhanced SFP/SFF-8472 compliant digital diagnostic capabilities that are critical for functionality and design flexibility. The chipset includes the VSC7964, a monolithic laser driver and post amplifier, and the VSC7977, a bandwidth-selectable transimpedance amplifier.

The VSC7964 and VSC7977 chipset architecture and pin placement has been optimized to reduce the bill of material cost and to simplify the assembly process to the point where all components, both active and passive, can fit on a single side of a four-layer printed circuit board. This chipset also requires 50% less external passive components than competitive solutions. The VSC7964 is the first device to integrate the VCSEL laser driver and post amplifier into a single integrated circuit, says Vitesse. The driver features automatic power control loop, adjustable negative peaking control, six integrated DACs, and a temperature sensor -- all of which reduce the need for external components.

With measured rise and fall times on both the transmitter and receiver of less than 40 psec, the VSC7964 exhibits 40% margin to the 4G Fibre Channel eye mask and greater than 50% margin to the 1G/2G eye mask. The sensitivity of the post amplifier is 3 mV differential, with a crosstalk penalty of less than 0.1 dB, corresponding to an optical sensitivity of -21 dBm at 4 Gbits/sec.

The VSC7977 optical sensitivity at the 4-Gbit/sec data rate adds over 6 dB of margin to the standard. The device also features 6 kOhms of transimpedance gain and incorporates a linear photo current monitor, on chip photodiode filter and extended temperature range operation of -40 to +105 degrees C.

The VSC7964 and VSC7977 is the only available chipset to offer bandwidth adjustment to meet the 4 Gbits/sec INCITS/T11 Fibre Channel standards, the company asserts. Through the rate select control input on the VSC7964, the bandwidth of both the post amplifier and TIA functions can be adjusted to one of four settings. This bandwidth selection capability provides module manufacturers with up to 2.5 dBm of additional receiver sensitivity at 1G data rates.

The VSC7964 has been designed to seamlessly operate with a standard microcontroller to provide the required SFP/SFF-8472 digital diagnostic capabilities. By communicating digitally through the use of the integrated DACs and a serial peripheral interface (SPI), the designer has complete access to the VSC7964 registers, such as the laser bias, modulation and peaking currents, and the LOS threshold settings, thus maximizing implementation flexibility and increasing the testability. This enhanced functionality can be used to reduce the calibration and test time, while enabling module manufacturers to differentiate their products by offering advanced diagnostic and management features not available when using a digital diagnostics chip-based solution.

Although the 8G Fibre Channel standard will not be completed until late 2005 or early 2006, indications are that the SFP form factor will be the module of choice. The power requirement and cost target will be similar to the 4G solution. Vitesse has already measured the VSC7964 performance at 8.5 Gbits/sec. Link performance at 850 nm was verified over 180 m of 50 micron multimode fiber that was compliant to the FC-PI-2 standard. This is a major step in confirming feasibility for the SFP form factor to support higher data rates.

The VSC7964 Laser Driver/Post Amplifier is sampling now and is available in a 40-pin, 6x6-mm QFP-N package. Samples of the VSC7977 will be available in September 2004 and will be sold in die form or as a complete optical receiver in a standard five-pin TO-46 package with a short wave PIN detector. The VSC7964YK and VSC7977-W laser driver, post amplifier, and TIA chipset is priced at $3.78 in production quantities.

More in Home