ACS8944 Semtech Corporation, ACS8944 Datasheet - Page 9

• Manufacturer Part Number: ACS8944
• Description: Jitter Attenuating, Multiplying Phase Locked Loop for Oc-12/stm-4
• Manufacturer: Semtech Corporation

Figure 9 Lock Filter Components
The filtering components are external so that the time to
indicate lock or not locked can be optimized for the
application. The output indicates both phase and
frequency lock. During off-frequency conditions the
LOCKB output will be predominately high in its PWM
generation with the filtered version giving a constant high
state.
Figure 10 Typical Application
Revision 3/November 2006 © Semtech Corp.
ADVANCED COMMUNICATIONS
Backplane
LOCKB
Master Clock
Master Sync
Slave Clock
Slave Sync
Stand-by Clock
Stand-by Sync
Primary Ref.
Input/
output
LOCK_B
Master Sync Card
Line Card (0C-12)
Recovered Clock
R3
470K
LINE
CARD
PROTECTION
Slave Sync Card
Line
Unit
I/F
C5
220nF
ACS8515
ACS8525
ACS8526
ACS8527
F8944_011Lockfilter_03
Low Jitter up to 155.52 MHz
DATA
DATA
CLK
GND
SSM
ACS8944
JAM PLL
SSM Processing
mP/Serial Bus
Multi Frame Sync
Frame Sync
Priorities
FINAL
Input CLK Sources
Page 9
E1/DS1
Clock
Distribution
Applications
The ACS8944 is targeted at applications requiring clock
cleaning at 19.44 MHz, 38.88 MHz, 77.76 MHz or
155.52 MHz where input jitter is filtered out or attenuated
at frequencies above the ACS8944 PLL bandwidth. It also
performs the function of a clock multiplying unit (CMU)
translating any one of these input frequencies to any one
of 19.44 MHz, 38.88 MHz, 77.76 MHz or 155.52 MHz
output frequencies.
The ACS8944 can save space when compared with
discrete analog + VCXO solutions or module-based
solutions. In the example in Figure 10 the ACS8944 is
shown symbolically as a low cost line card dejittering
device. The ACS8944 carries out the appropriate
frequency multiplication for onward distribution as
required by the line card.
SEC
Priorities
Config.
TCLK
FRAMER
Clock
Distribution
Low Jitter/Low Skew
SETS
ACS8510
ACS8520
ACS8522
ACS8530
SERDES
Output
CLKs
ACS8944 JAM PLL
Multiple Line cards
To/from
SONET/SDH/PDH
Network
SetsLinecardGenApp_08
DATASHEET
www.semtech.com