ACS8946 Semtech Corporation, ACS8946 Datasheet - Page 23

• Manufacturer Part Number: ACS8946
• Description: Jitter Attenuating, Multiplying Phase Locked Loop, with Protection Switch, for Oc-12/stm-4 and GbE
• Manufacturer: Semtech Corporation

Example Schematic
Figure 13 Generic Line Card Clock Source with Protection - Example Schematic
Revision 3/November 2006 © Semtech Corp.
ADVANCED COMMUNICATIONS
DOWNSTREAM
DEVICE
DOWNSTREAM
DEVICE
CMOS
RECEIVER
LVPECL
RECEIVER
LVPECL
RECEIVER
AGND
SYNC CLOCK
OUTPUT
(Single ended)
OUT1N
OUT1P
OUT2N
OUT2P
R22
130R
R26
130R
R31
82R
R30
82R
R24
82R
R20
82R
Note...
VDDA3
R27
130R
VDDA3
R23
130R
SYNC
C20
100pF
VDDA
R25
82R
R21
82R
AGND3
AGND3
Loop
Filter
Components
(place as
close as
possible to
device pins)
SW4 RESET
AGND2
F
Transmission
Line
130R
AGND
R32
R33
130R
or optimal performance use a Low Voltage Dropout (LDO) Regulator to supply VDDA2
AGND
C21
10nF
Instant Rate Control
for OUT1 and OUT2
Transmission
Line
0 0 19.44 MHz
0 1 77.76 MHz
1 0 155.52 MHz
1 1 622.08 MHz
Transmission
Line
C24
100nF
A B
SYNC CLOCK
INPUT to ACS8946
(Differential)
VDDA
C3
C1
C2
C4
VDDA
Frequency
SW3
(Rate2A
Rate2B)
SW2
(Rate1A
Rate1B)
R1
R2
R28
10K
AGND2
UPSTREAM DEVICE (e.g. SETS function)
C19
10nF
= Logic 0
= Logic 1
VDDA
VDDA
All decoupling capacitors to be placed as close as possible to the ACS8946 device.
Where possible, star connect VDDA2 and AGND2 to clean power and ground sources.
C25 100pF
C22 100uF
C18
100pF
C23 10nF
AGND
10nF
C5
C17
10nF
VDDA2
CLK1
EXT. FB.
Source Selection
R29
Zero
Ohm
Link
C16
100pF
100pF
C6
FINAL
Page 23
C15
10nF
37 IC1
38 VDDOSC
39 VSSOSC
40 RESETB
41 SYNCP
42 SYNCN
43 VDDP2
44 SYNC_OUT
45 RATE2A
46 RATE2B
47 RATE1A
48 RATE1B
AGND
CLK2
AUTO
C14
10nF
VDDA
R3
82R
R4
82R
R5
82R
R6
82R
AGND
SW1
CLK2
C13
100pF
Transmission
Line
C12
10nF
ALARMC_CO3 16
ALARM2_CO1 14
ALARM1_CO0 13
VDDA2
C10 100pF
CFG-OUT2 15
R7
130R
R9
130R
C8 10nF
C9 100pF
R8
130R
R10
130R
CLK1
C7 10nF
CFG_IN6 24
CFG_IN5 23
CFG_IN4 22
CFG_IN3 21
CFG_IN2 20
CFG_IN1 19
CFG_IN0 18
LOCKB 17
R12 51R
Transmission
Line
R16 51R
Transmission
Line
R13 51R
R17 51R
VDDA
Transmission
Line
AGND
ACS8946 JAM PLL
VDDA
VDDA
REFERENCE CLOCK
INPUT to ACS8946
(Differential)
R14
51R
R18
51R
VDDA
VDDA4
R15
51R
VDDA4
R19
51R
AGND
F8946D_021ExSchematicMG_05
Outputs from Input
Activity Alarms:
C11
220nF
R11
470KR
OUTPUTS 3 and 4
Rate selection
on Power-up
OUT4 =
622.08 MHz
DOWNSTREAM
DEVICE
CML
RECEIVER
OUT3 =
19.44 MHz
DOWNSTREAM
DEVICE
CML
RECEIVER
DATASHEET
www.semtech.com
AGND
ALARMC
ALARM2
ALARM1
LOCKB