GENERAL DESCRIPTION
The XRT91L81 is a fully integrated SONET/SDH transceiver for applications in SONET OC-48 and SDH STM-16 (2.488 Gbps) or 2.666 Gbps systems allowing use of the Forward Error Correction (FEC) capability. The device 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 155.52/77.76 MHz (166/83.3 MHz) external clock references.

FEATURES
• Single-chip fully integrated solution containing serializer/deserializer (SerDes), clock multiplier unit (CMU), 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 10 mV-pp
• 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 Implementation 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 timed mode
• Diagnostic features include various lock detect functions
• Meets Telcordia, ANSI and ITU-T jitter requirements
• Operates at 1.8V with 3.3V I/O
• 600 mW 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 and Routers
• DSLAMS
• SONET/SDH Test Equipment
• DWDM Termination Equipment
• Optical Modules and Sub-Systems