GENERAL DESCRIPTION
The AD9557 is a low loop bandwidth clock multiplier that provides jitter cleanup and synchronization for many systems, including synchronous optical networks (OTN/SONET/SDH). The AD9557 generates an output clock synchronized to up to four external input references. The digital PLL allows for reduction of input time jitter or phase noise associated with the external references. The digitally controlled loop and holdover circuitry of the AD9557 continuously generates a low jitter output clock even when all reference inputs have failed.

FEATURES
   Supports GR-1244 Stratum 3 stability in holdover mode
   Supports smooth reference switchover with virtually
      no disturbance on output phase
   Supports Telcordia GR-253 jitter generation, transfer, and
      tolerance for SONET/SDH up to OC-192 systems
   Supports ITU-T G.8262 synchronous Ethernet slave clocks
   Supports ITU-T G.823, G.824, G.825, and G.8261
   Auto/manual holdover and reference switchover
   2 reference inputs (single-ended or differential)
   Input reference frequencies: 2 kHz to 1250 MHz
   Reference validation and frequency monitoring (1 ppm)
   Programmable input reference switchover priority
   20-bit programmable input reference divider
   2 pairs of clock output pins, with each pair configurable as
      a single differential LVDS/HSTL output or as 2 single-ended
      CMOS outputs
   Output frequencies: 360 kHz to 1250 MHz
   Programmable 17-bit integer and 23-bit fractional
      feedback divider in digital PLL
   Programmable digital loop filter covering loop bandwidths
      from 0.1 Hz to 5 kHz (2 kHz maximum for <0.1 dB of peaking)
   Low noise system clock multiplier
   Frame sync support
   Adaptive clocking
   Optional crystal resonator for system clock input
   On-chip EEPROM to store multiple power-up profiles
   Pin program function for easy frequency translation
      configuration
   Software controlled power-down
   40-lead, 6 mm × 6 mm, LFCSP package

APPLICATIONS
   Network synchronization, including synchronous Ethernet
      and SDH to OTN mapping/demapping
   Cleanup of reference clock jitter
   SONET/SDH/OTN clocks up to 100 Gbps, including FEC
   Stratum 3 holdover, jitter cleanup, and phase transient control
   Wireless base station controllers
   Cable infrastructure
   Data communications