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