ACS8946 Semtech Corporation, ACS8946 Datasheet

ACS8946

Manufacturer Part Number

ACS8946

Description

Jitter Attenuating, Multiplying Phase Locked Loop, with Protection Switch, for Oc-12/stm-4 and GbE

Manufacturer

Semtech Corporation

Datasheet

1.ACS8946.pdf (40 pages)

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The ACS8946 JAM PLL is a Jitter-Attenuating, Multiplying

differential Phase-Locked Loop, for generating low jitter

output clocks compliant up to SONET OC-12 and STM-4

622.08 MHz specifications. Its primary function is to

clean up clock jitter for high performance optical line

cards with OC-12 framers and serializers. It also provides

reference switching functionality for line card protection,

and frequency translation.

Typical output jitter generation is within OC-12/STM-4

specifications, at 2.8 ps rms, making it an ideal dejittering

solution for use with Semtech clock and line card parts:

ACS8510, ACS8520, ACS8522 and ACS8530. The

ACS8946 can also be used as a basic line card protection

device in some applications.

The ACS8946 JAM PLL has two differential, frequency

programmable, LVPECL reference inputs and one

differential sync input. It has four outputs, programmable

as LVPECL or CML, and frequency programmable to any

common SONET/SDH rate i.e. 19.44 MHz, 38.88 MHz,

77.76 MHz, 155.52 MHz, 311.04 MHz and 622.08 MHz.

Jitter cleaning of Gigabit Ethernet (GbE) 125 MHz and

156.25 MHz is also possible, with output frequency

multiplication up to 625.00 MHz available.

The device's operating bandwidth (and consequently the

jitter attenuation point relating to this bandwidth) is fully

configurable, and is set by external passive components.

Note...For items marked

in the Reference Section on page 38.

Figure 1 Simplified Block Diagram of the ACS8946 JAM PLL

Revision 3/November 2006 © Semtech Corp.

Introduction

ADVANCED COMMUNICATIONS

Block Diagram

ADVANCED COMMUNICATIONS

Device Configuration Select:

1 x LVPECL

Differential Sync Input

2 x LVPECL

Differential

Input References

Programmable:

19.44 MHz to

156.25 MHz

Note: LOS alarm outputs are also

used for device config. select

Clock Input Configuration for:

- Manual selection

- Auto Ref selection

- External feedback mode

(SEL_CLK2, AUTO_SEL)

CFG_IN[7:0]

CFG_OUT2

[1],[2], etc.

CLK2

SYNC

CLK1

references are given in full

Selector

Input

RESETB

Control and Monitor

LOS Alarms for:

- CLK1 (ALARM1_CO0)

- CLK2 (ALARM2_CO1)

- Currently selected reference (ALARMC_CO3)

Divider

Lock Alarm (LOCKB)

Charge

Pump

PFD

FINAL

Page 1

Loop

Filter

Features

Jitter Attenuating, Multiplying Phase Locked Loop,

with Protection Switch, for OC-12/STM-4 and GbE

Meets rms jitter requirements of:

PLL bandwidth and jitter peaking fully adjustable—

supports PLL loop bandwidths from 2 kHz for superior

input jitter filtering

Typical jitter generation down to:

ITU, ETSI and Telcordia frequency band results shows

exceptional performance in a “Real World”

environment (low PLL bandwidth of 2 KHz and a

typical input from an ACS8525 partner IC):

Tracking range ±400 ppm about a wide range of input

frequencies

Manual or automatic control of reference selection

External feedback option

LOS alarms for each input, and for selected reference

3.3 V operation, - 40 to +85°C temperature range

Small outline leadless 7 mm x 7 mm QFN48 package

Lead (Pb)-free version available (ACS8946T),

RoHS

2.5 GHz

VCO

Telcordia GR-253

ITU-T G.813

ETSI EN300-462-7

0.3 ps rms for 250 kHz to 5 MHz band for G.813,

2.8 ps rms for 12 kHz to 20 MHz band (against

0.4 ps rms for 250 kHz to 5 MHz band for G.813,

2.8 ps rms for 12 kHz to 20 MHz band

rates

or EN300 462, at STM-4 (OC-12) rates

4.02 ps rms for GR-253-CORE at OC-48 rate)

or EN300 462, at STM-4 (OC-12) rates

[11]

Frequency Select

(RATE[2:1]A, RATE[2:1]B)

and WEEE

Re-timing

Frequency

Dividers

Drivers

Clock

[4]

/G.812

ACS8946 JAM PLL

[12]

[8]

SYNC_OUT

OUT[4:1]

[1]

for OC-3 and OC-12

compliant

/EN302-084

[3]

F8946D_004Blockdiag_06

1 x CMOS

Single-ended

Sync Output

4 x LVPECL or CML

Output Clocks,

Independently

Programmable

from:

625.00 MHz

622.08 MHz

311.04 MHz

155.52 MHz

77.76 MHz

38.88 MHz

19.44 MHz

125 MHz

156.25 MHz

Others Ethernet rates

available using divider

for STM-1 and STM-4 rates

[2]

DATASHEET

www.semtech.com

up to STM-16

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