ACS8946 datasheet(22/40 Pages) SEMTECH

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ADVANCED COMMUNICATIONS

FINAL

DATASHEET

Revision 3/November 2006 © Semtech Corp.

Page 22

www.semtech.com

ACS8946 JAM PLL

Applications

The ACS8946 is targeted at applications requiring clock

cleaning, where input jitter is filtered out or attenuated at

frequencies above the ACS8946 PLL bandwidth, and at

those requiring protection switching. It also performs the

function of a clock multiplying unit (CMU) translating from

one common spot frequency to one of six spot

frequencies (and/or odd divisions thereof) independently

on each of its four outputs.

The ACS8946 can save space when compared with

discrete analog + VCXO solutions or module-based

solutions. In the example in Figure 12 the ACS8946 is

shown symbolically as a line card dejittering and clock

multiplying device, providing additional jitter cleaning and

frequency translation of the output clocks from a Semtech

Line Card Protection device.

Figure 13 shows a non-specific example schematic which

represents a generic line card design, and demonstrates

the I/O connections, configuration controls on the device

and the appropriate terminations in different

CML/LVPECL technologies, with only the parts relevant to

the handling of clocks being shown. This example could

be used as a solution for less stringent applications where

the ACS8946 could carry out the basic clock protection

function in place of a Semtech Line Card Protection

device, although it could not, for example, perform group

(Clock and Sync) switching, frequency monitoring, or other

functions available with members of the Semtech LC/P

family of parts.

Application Diagram

Figure 12 Typical Application for Semtech JAM PLLs

Multiple Line cards

Primary Ref.

Input/

output

Master Sync Card

Slave Sync Card

uP/Serial Bus

SSM

Priorities

TCLK

CLK

SEC

Master Clock

DATA

Priorities

Config.

Input CLK Sources

Line

I/F

Unit

SetsLinecardGenApp_11

To/from

SONET/SDH/PDH

Network

FRAMER

SERDES

Line Card (0C-12)

Master Clock

Recovered Clock

Sync

Slave Clock

Backplane

Low Jitter/Low Skew

Low Jitter spot frequencies to 625.00 MHz

Sync

4 x Programmable Clocks

JAM PLL with

PROTECTION

SWITCH

SETS

Output

CLKs

ACS8946

ACS8510

ACS8520

ACS8522

ACS8530

Clock

Distribution

SSM Processing

Slave Clock

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