Vitesse Semiconductor has announced a chipset specifically designed for multirate Fibre Channel and Gigabit Ethernet SFP modules that can operate up to 4GBit/sec.
The chipset comprises 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 optimised 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.
Vitesse claims that the 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. The driver features automatic power control loop, adjustable negative peaking control, six integrated digital-to- analog converters (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 Gbps.
The VSC7977 optical sensitivity at the 4 Gbit/sec data rate adds over 6dB of margin to the standard. The device also features 6kÎ© of transimpedance gain and incorporates a linear photo current monitor, on chip photodiode filter and extended temperature range operation of -40 degrees C to +105 degrees C.
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, maximising the performance at the configured data rate and ensuring backward compatibility with the legacy technology currently deployed. The bandwidth selection capability provides module manufactures with up to 2.5dBm of additional receiver sensitivity at 1G data rates.
The VSC7964 has been designed to operate with a standard microcontroller to provide the required SFP/SFF-8472 Digital Diagnostic capabilities.
By communicating digitally through the use of integrated DACs and a Serial Peripheral Interface (SPI), a designer has complete access to the VSC7964 registers, such as the laser bias, modulation and peaking currents, and the LOS threshold settings.
The VSC7964 Laser Driver/Post Amplifier is sampling now and is available in a 40-pin, 6 mm x 6 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 5-pin TO-46 package with a short wave PIN detector.