GENERAL DESCRIPTION
The XRT91L81 is a fully integrated SONET/SDH transceiver block for applications in SONET OC-48 allowing the use of Forward Error Correction (FEC) capability. The transceiver includes an on-chip Clock Multiplier Unit (CMU), which uses a high frequency Phase-Locked Loop (PLL) to generate the highspeed transmit serial clock from slower external clock references. It also provides Clock and Data Recovery (CDR) functions by synchronizing its on-chip Voltage Controlled Oscillator (VCO) to the incoming serial data stream.

FEATURES
• 2.488 / 2.666 Gbps Transceiver
• Single-chip fully integrated solution containing parallel-to-serial converter, clock multiplier unit (CMU), serial-to-parallel converter, limiting amplifier and clock data recovery (CDR) functions
• Host mode serial microprocessor interface simplifies monitor and control
• Provides support for dual fiber rings
• Integrated limiting amplifier accepts differential inputs down to 10mVp-p
• Separate reference and VCXO input ports support multiple de-jittering modes
• On-chip phase detector and charge pump for external VCXO based de-jittering PLL
• Targeted for SONET OC-48/SDH STM-16 Applications
• Selectable full duplex operation between standard rate of 2.488 Gbps or Forward Error Correction rate of 2.666 Gbps
• 4-bit LVDS data paths at 622/666 MHz complies with OIF SFI-4 Implimentation Agreement
• Internal FIFO decouples transmit input and output clocks
• Tx CMU and Rx CDR lock detect
• Provides Local, Remote and Split Loop-Back modes as well as Loop Timing mode
• Diagnostics features include various lock detect functions
• Meets Telcordia, ANSI and ITU-T jitter requirements
• Operates at 1.8V with 3.3V I/O
• 600mW Typical Power Dissipation
• Package: 12 x 12 mm 196-pin STBGA

APPLICATIONS
• SONET/SDH-based Transmission Systems
• Add/Drop Multiplexers
• Cross Connect Equipment
• ATM and Multi-Service Switches, Routers and Switch/Routers
• DSLAMS
• SONET/SDH Test Equipment
• DWDM Termination Equipment
• Optical Modules and Sub-Systems