SILABS Si5315A-C-GM

Si5315
S Y N C H R O N O U S E T H E R N E T / TE L E C O M J I T T E R A T T E N U A T I N G
CLOCK MULTIPLIER
Features







Provides jitter attenuation and frequency 
translation between SONET/PDH and
Ethernet

Supports ITU-T G.8262 Synchronous
Ethernet equipment slave clock (EEC
option 1 and 2) requirements with

optional Stratum 3 compliant timing card
clock source
Two clock inputs/two clock outputs

Input frequency range: 8 kHz–644 MHz 
Output frequency range: 8 kHz–644 MHz 
Ultra low jitter:
0.23 ps RMS (1.875–20 MHz)

0.47 ps RMS (12 kHz–20 MHz)

Simple pin control interface

Selectable loop bandwidth for jitter
attenuation: 60 to 8.4 kHz
Automatic/Manual hitless switching
and holdover during loss of inputs
clock
Programmable output clock signal
format: LVPECL, LVDS, CML or
CMOS
40 MHz crystal or XO reference
Single supply: 1.8, 2.5, or 3.3 V
On-chip voltage regulator with high
PSRR
Loss of lock and loss of signal alarms
Small size: 6 x 6 mm, 36-QFN
Wide temperature range: –40 to
+85 ºC
Ordering Information:
See page 48.
Applications
CKOUT1–
CKOUT1+
SFOUT1
GND
SFOUT0
VDD
NC
Description
CKOUT2–
Pin Assignments
Carrier Ethernet switches routers
MSAN / DSLAM
T1/E1/DS3/E3 line cards
CKOUT2+



Synchronous Ethernet line cards
SONET OC-3/12/48 line cards
PON OLT/ONU
36 35 34 33 32 31 30 29 28
27 FRQSEL3
FRQTBL 2
26 FRQSEL2
LOS1 3
25 FRQSEL1
LOS2 4
VDD 5
XA 6
XB
24 FRQSEL0
GND
Pad
23 BWSEL1
22 BWSEL0
7
21 CS_CA
GND 8
20 GND
19 GND
AUTOSEL 9
LOL
CKIN1–
GND
CKIN1+
DBL2_BY
CKIN2–
CKIN2+
10 11 12 13 14 15 16 17 18
VDD
The Si5315 is a jitter-attenuating clock multiplier for Gb and 10G Synchronous
Ethernet, SONET/SDH, and PDH (T1/E1) applications. The Si5315 supports SyncE
EEC options 1 and 2 when paired with a timing card that implements the required
wander filter. The Si5315 accepts dual clock inputs ranging from 8 kHz to 644.53 MHz
and generates two equal frequency-multiplied clock outputs ranging from 8 kHz to
644.53 MHz. The input clock frequency and clock multiplication ratio are selectable
from a table of popular SyncE and T1/E1 rates. The Si5315 is based on Silicon
Laboratories' third-generation DSPLL® technology, which provides any-frequency
synthesis and jitter attenuation in a highly integrated PLL solution that eliminates the
need for external VCXO and loop filter components. The DSPLL loop bandwidth is
user programmable, providing jitter performance optimization at the application level.
RST 1
XTAL/CLOCK



Functional Block Diagram
XTAL/Clock
Si5315
Clock Out 1
Clock In 1
®
Output Signal Format[1:0]
DSPLL
Clock In 2
Clock Out 2
Loss of Lock
Loss of Signal 1
Loss of Signal 2
Clock 2 Disable/PLL Bypass
Status/Control
VDD (1.8, 2.5, or 3.3 V)
GND
Frequency Select[3:0]
Frequency Table Select
Loop Bandwidth Select[1:0]
Rev. 1.0 4/12
Manual/Auto Clock Selection
Clock Switch/Clock Active Indicator
XTAL/Clock
Copyright © 2012 by Silicon Laboratories
Si5315
Si5315
2
Rev. 1.0
Si5315
TABLE O F C ONTENTS
Section
Page
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.1. Three-Level (3L) Input Pins (No External Resistors) . . . . . . . . . . . . . . . . . . . . . . . .11
1.2. Three-Level (3L) Input Pins (With External Resistors) . . . . . . . . . . . . . . . . . . . . . . . 12
2. Typical Application Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
3. System Level Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2. PLL Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5. Frequency Plan Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
5.1. Frequency Multiplication Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
5.2. PLL Self-Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.3. Input Clock Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.4. Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.5. Holdover Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.6. PLL Bypass Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6. High-Speed I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6.1. Input Clock Buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6.2. Output Clock Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
7. Crystal/Reference Clock Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
7.1. Crystal/Reference Clock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
8. Power Supply Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
9. Typical Phase Noise Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
9.1. 10G LAN SyncE Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10. Pin Descriptions: Si5315 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
11. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
12. Package Outline: 36-Pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
13. PCB Land Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
14. Top Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
14.1. Si5315 Top Marking (QFN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
14.2. Top Marking Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
Rev. 1.0
3
Si5315
1. Electrical Specifications
Table 1. Recommended Operating Conditions
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Symbol
Temperature Range
Supply Voltage
Test Condition
Min
Typ
Max
Unit
–40
25
85
ºC
3.3 V nominal
2.97
3.3
3.63
V
2.5 V nominal
2.25
2.5
2.75
V
1.8 V nominal
1.71
1.8
1.89
V
TA
VDD
Note: All minimum and maximum specifications are guaranteed and apply across the recommended operating conditions.
Typical values apply at nominal supply voltages and an operating temperature of 25 °C unless otherwise noted.
Table 2. DC Characteristics
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Supply Current (Supply
current is independent of
VDD)
Symbol
Test Condition
Min
Typ
Max
Units
IDD
LVPECL Format
644.53125 MHz Out
All CKOUTs Enabled1
—
251
279
mA
LVPECL Format
644.53125 MHz Out
Only 1 CKOUT Enabled1
—
217
243
mA
CMOS Format
25.00 MHz Out
All CKOUTs Enabled2
—
204
234
mA
CMOS Format
25.00 MHz Out
Only CKOUT1 Enabled2
—
194
220
mA
1.8 V ± 5%
0.9
—
1.4
V
2.5 V ± 10%
1.0
—
1.7
V
3.3 V ± 10%
1.1
—
1.95
V
Single-ended
20
40
60
k
0
—
VDD
V
CKINn Input Pins
Input Common Mode Voltage
(Input Threshold Voltage)
VICM
Input Resistance
CKNRIN
Input Voltage Level Limits
CKNVIN
Notes:
1. Refers to Si5315A speed grade.
2. Refers to Si5315B speed grade.
3. This is the amount of leakage that the 3L inputs can tolerate from an external driver. See Figure 3 on page 11.
4
Rev. 1.0
Si5315
Table 2. DC Characteristics (Continued)
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Symbol
Test Condition
Min
Typ
Max
Units
VISE
fCKIN < 212.5 MHz
See Figure 2.
0.2
—
—
VPP
fCKIN > 212.5 MHz
See Figure 2.
0.25
—
—
VPP
fCKIN < 212.5 MHz
See Figure 2.
0.2
—
—
VPP
fCKIN > 212.5 MHz
See Figure 2.
0.25
—
—
VPP
VOCM
LVPECL 100  load
line-to-line
VDD –
1.42
—
VDD –
1.25
V
Differential Output Swing
VOD
LVPECL 100  load
line-to-line
1.1
—
1.9
VPP
Single Ended Output Swing
VSE
LVPECL 100  load
line-to-line
0.5
—
0.93
VPP
Differential Output Voltage
CKOVD
CML 100  load
line-to-line
350
425
500
mVPP
Common Mode
Output Voltage
CKOVCM
CML 100  load
line-to-line
—
VDD –
0.36
—
V
Differential
Output Voltage
CKOVD
LVDS 100  load
line-to-line
500
700
900
mVPP
Low swing LVDS 100  load
line-to-line
350
425
500
mVPP
CKOVCM
LVDS 100  load
line-to-line
1.125
1.2
1.275
V
CKORD
CML, LVPECL, LVDS,
Disable
—
200
—

Output Voltage Low
CKOVOLLH
CMOS
—
—
0.4
V
Output Voltage High
CKOVOHLH
VDD = 1.71 V
CMOS
0.8 x VDD
—
—
V
Single-ended Input Voltage
Swing
Differential Input
Voltage Swing
VID
CKOUTn Output Clocks
Common Mode
Common Mode
Output Voltage
Differential Output Resistance
Notes:
1. Refers to Si5315A speed grade.
2. Refers to Si5315B speed grade.
3. This is the amount of leakage that the 3L inputs can tolerate from an external driver. See Figure 3 on page 11.
Rev. 1.0
5
Si5315
Table 2. DC Characteristics (Continued)
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Output Drive Current
Symbol
Test Condition
Min
Typ
Max
Units
CKOIO
CMOS
Driving into CKOVOL for output low or CKOVOH for output high. CKOUT+ and
CKOUT– shorted externally.
VDD = 1.71 V
7.5
—
—
mA
VDD = 2.97 V
32
—
—
mA
VDD = 1.71 V
—
—
0.5
V
VDD = 2.25 V
—
—
0.7
V
VDD = 2.97 V
—
—
0.8
V
VDD = 1.89 V
1.4
—
—
V
VDD = 2.25 V
1.8
—
—
V
VDD = 3.63 V
2.5
—
—
V
2-Level LVCMOS Input Pins
Input Voltage Low
Input Voltage High
VIL
VIH
Input Low Current
IIL
—
—
50
µA
Input High Current
IIH
—
—
50
µA
Weak Internal Input Pull-up
Resistor
RPUP
—
75
—
k
Weak Internal Input
Pull-down Resistor
RPDN
—
75
—
k
Input Voltage Low
VILL
—
—
0.15 x VDD
V
Input Voltage Mid
VIMM
0.45 x VDD
—
0.55 x VDD
V
Input Voltage High
VIHH
0.85 x VDD
—
—
V
Input Low Current
IILL
See note 3.
–20
—
—
µA
Input Mid Current
IIMM
See note 3.
–2
—
2
µA
Input High Current
IIHH
See note 3.
—
—
20
µA
3-Level Input Pins
Notes:
1. Refers to Si5315A speed grade.
2. Refers to Si5315B speed grade.
3. This is the amount of leakage that the 3L inputs can tolerate from an external driver. See Figure 3 on page 11.
6
Rev. 1.0
Si5315
Table 2. DC Characteristics (Continued)
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Symbol
Test Condition
Min
Typ
Max
Units
VOL
IO = 2 mA
VDD = 1.62 V
—
—
0.4
V
IO = 2 mA
VDD = 2.97 V
—
—
0.4
V
IO = –2 mA
VDD = 1.62 V
VDD – 0.4
—
—
V
IO = –2 mA
VDD = 2.97 V
VDD – 0.4
—
—
V
RST = 0
–100
—
100
µA
—
12
—
k
LVCMOS Output Pins
Output Voltage Low
Output Voltage High
Disabled Leakage Current
VOH
IOZ
Single-Ended Reference Clock Input Pin XA (XB with Cap to Gnd)
XTAL/CLOCK = M
Input Resistance
XARIN
Input Voltage Level Limits
XAVIN
0
—
1.2
V
Input Voltage Swing
XAVPP
0.5
—
1.2
VPP
—
12
—
k
Differential Reference Clock Input Pins (XA/XB)
XTAL/CLOCK = M
Input Resistance
XA/XBRIN
Differential Input Voltage
Level Limits
XA/XBVIN
0
—
1.2
V
XAVPP/XBVPP
0.5
—
2.4
VPP
Input Voltage Swing
Notes:
1. Refers to Si5315A speed grade.
2. Refers to Si5315B speed grade.
3. This is the amount of leakage that the 3L inputs can tolerate from an external driver. See Figure 3 on page 11.
Rev. 1.0
7
Si5315
Table 3. AC Characteristics
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Input Frequency
Symbol
Test Condition
Min
Typ
Max
Units
0.008
—
644.53
MHz
40
—
60
%
2
—
—
ns
—
—
3
pF
20–80%
See Figure 2
—
—
11
ns
Note 2
0.008
—
644.53
MHz
Note 3
0.008
—
125
MHz
CKNF
CKINn Input Pins
Input Duty Cycle (Minimum
Pulse Width)
CKNDC
Input Capacitance
CKNCIN
Input Rise/Fall Time
CKNTRF
Whichever is smaller1
CKOUTn Output Pins
Output Frequency (Output not
configured for CMOS or disable)
CKOF
Maximum Output Frequency in
CMOS Format
CKOFMC
—
—
161.13
MHz
Output Rise/Fall (20–80%) at
644.5313 MHz
CKOTRF Output not configured for CMOS
or disabled, see Figure 2
—
230
350
ps
CMOS Output
VDD = 1.62
Cload = 5 pF
—
—
8
ns
CMOS Output
VDD = 2.97
Cload = 5 pF
—
—
2
ns
100  Load
Line to Line
Measured at 50% Point
(not for CMOS)
—
—
±40
ps
—
—
3
pF
Single Ended Output Rise/Fall
(20–80%)
CKOTRF
Output Duty Cycle Differential
Uncertainty
CKODC
LVCMOS Pins
Input Capacitance
Cin
Notes:
1. Assumes N3 does not equal 1. IF N3 = 1, CKNDC = 50 µs.
2. Refers to Si5315A speed grade.
3. Refers to Si5315B speed grade.
8
Rev. 1.0
Si5315
Table 3. AC Characteristics (Continued)
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Symbol
Test Condition
Min
Typ
Max
Units
tRF
CLOAD = 20 pf
See Figure 2
—
25
—
ns
From last CKINn  to
internal detection of LOSn
—
—
750
µs
tCLRLOL
LOS to  LOL
Assume Fold=Fnew,
Stable XA-XB reference
—
10
—
ms
Output Clock Skew
tSKEW
of CKOUTn to CKOUTn
—
—
100
ps
Phase Change Due to
Temperature Variation
tTEMP
Maximum phase change from
–40 to +85 °C
—
300
500
ps
—
1200
—
ms
—
0.05
0.1
dB
LVCMOS Output Pins
Rise/Fall Times
LOSn Trigger Window
Time to Clear LOL after LOS
Cleared
LOSTRIG
PLL Performance
Lock Time
Closed Loop Jitter Peaking
Jitter Tolerance
Minimum Reset Pulse Width
Output Clock Initial Phase Step
tLOCKHW RST with valid CKIN to LOL;
BW = 100 Hz
JPK
tRSTMIN
tP_STEP
Holdover Frequency Historical
Averaging Time
tHISTAVG
Holdover Frequency Historical
Delay Time
tHISTDEL
Spurious Noise
See 4.2.3. "Jitter Tolerance" on page 18.
JTOL
SPSPUR
During clock switch CKIN > 19.44
MHz
Max spur @ n x f3
(n > 1, n x f3 < 100 MHz)
ns pkpk
1
—
—
µs
—
100
200
ps
—
6.7
—
sec
—
26.2
—
ms
—
–75
—
dBc
Notes:
1. Assumes N3 does not equal 1. IF N3 = 1, CKNDC = 50 µs.
2. Refers to Si5315A speed grade.
3. Refers to Si5315B speed grade.
Rev. 1.0
9
Si5315
Table 4. Jitter Generation
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Parameter
Symbol
Jitter Gen OC-192
JGEN
Jitter Gen OC-48
JGEN
IEEE 802.3 GbE
RMS Jitter
JGEN
Min
Typ
Max
GR-253 Spec
Unit
—
—
—
0.483
0.302
0.467
0.628
0.392
0.607
psrms
psrms
psrms
167 Hz5
—
0.470
0.611
0.012–20
111 Hz6
—
0.565
0.734
N/A
N/A
1.0 psrms
(0.01 UIrms
4.02 psrms
(0.01 UIrms)
4.02 psrms
(0.01 UIrms)
1.875–20
83 Hz6
—
0.232
0.301
Test Condition1,2,3,4
Measuremen DSPLL BW1
t Filter (MHz)
0.02–80
167 Hz5
4–80
167 Hz5
0.05–80
167 Hz5
psrms
psrms
psrms
Notes:
1. BWSEL [1:0] loop bandwidth settings provided in Table 9 on page 20.
2. 40 MHz fundamental mode crystal used as XA/XB input.
3. VDD = 2.5 V
4. TA = 85 °C
5. Si5315A test condition: fIN = 19.44 MHz, fOUT = 156.25 MHz, LVPECL clock input: 1.19 Vppd with 0.5 ns rise/fall time
(20–80%), LVPECL clock output.
6. Si5315B test condition: fIN =19.44 MHz, fOUT = 125 MHz, LVPECL clock input: 1.19 Vppd with 0.5 ns rise/fall time (2080%), LVPECL clock output.
V
SIGNAL +
Differential I/Os VICM , VOCM
SIGNAL –
VISE , VOSE
(SIGNAL +) – (SIGNAL –)
Single-Ended
Peak-to-Peak Voltage
Differential
Peak-to-Peak Voltage
VID,VOD
VICM, VOCM
t
SIGNAL +
VID = (SIGNAL+) – (SIGNAL–)
SIGNAL –
Figure 1. CKIN Voltage Characteristics
80%
DOUT, CLOUT
20%
tF
tR
Figure 2. Rise/Fall Time Characteristics
10
Rev. 1.0
Si5315
1.1. Three-Level (3L) Input Pins (No External Resistors)
Si5315
VDD
75 k
Iimm
75 k
External Driver
Figure 3. Three-Level Input Pins
Table 5. Three-Level Input Pins (No External Resistors)
Parameter
Symbol
Min
Max
Input Voltage Low
Vill
—
0.15 x VDD
Input Voltage Mid
Vimm
0.45 x VDD
0.55 x VDD
Input Voltage High
Vihh
0.85 x VDD
—
Input Low Current
Iill
–6 µA
—
Input Mid Current
Iimm
–2 µA
2 µA
Input High Current
Iihh
—
6 µA
Note: The above currents are the amount of leakage that the 3L inputs can tolerate from an external driver.
Rev. 1.0
11
Si5315
1.2. Three-Level (3L) Input Pins (With External Resistors)
V DD
Iimm
External Driver
V DD
Si5315
18 k
75 k
18 k
75 k
One of eight resistors from a Panasonic EXB-D10C183J
(or similar) resistor pack
Figure 4. Three Level Input Pins
Table 6. Three-Level Input Pins (With External Resistors)
Parameter
Symbol
Min
Max
Input Low Current
Iill
–30 µA
—
Input Mid Current
Iimm
–11 µA
–11 µA
Input High Current
Iihh
—
–30 µA
Note: The above currents are the amount of leakage that the 3L inputs can tolerate from an external driver.

Any resistor pack may be used.
The
Panasonic EXB-D10C183J is an example.
layout is not critical.
PCB

Resistor packs are only needed if the leakage current of the external driver exceeds the listed currents.
 If a pin is tied to ground or VDD, no resistors are needed.

12
If a pin is left open (no connect), no resistors are needed.
Rev. 1.0
Si5315
Table 7. Thermal Characteristics
(VDD = 1.8 ±5%, 2.5 ±10%, or 3.3 V ±10%, TA = –40 to 85 ºC)
Symbol
Test Condition
Min
Typ
Max
Unit
Thermal Resistance
Junction to Ambient
JA
Still Air
—
32
—
ºC/W
Thermal Resistance
Junction to Case
JC
Still Air
—
14
—
ºC/W
Parameter
Table 8. Absolute Maximum Limits
Symbol
Value
Unit
DC Supply Voltage
VDD
–0.5 to 3.8
V
LVCMOS Input Voltage
VDIG
–0.3 to (VDD + 0.3)
V
CKINn Voltage Level Limits
CKNVIN
0 to VDD
V
XA/XB Voltage Level Limits
XAVIN
0 to 1.2
V
Operating Junction Temperature
TJCT
–55 to 150
C
Storage Temperature Range
TSTG
–55 to 150
C
2
kV
ESD MM Tolerance; All pins except CKIN+/CKIN–
150
V
ESD HBM Tolerance (100 pF, 1.5 kΩ); CKIN+/CKIN–
750
V
ESD MM Tolerance; CKIN+/CKIN–
100
V
Parameter
ESD HBM Tolerance (100 pF, 1.5 kΩ); All pins except
CKIN+/CKIN–
Latch-Up Tolerance
JESD78 Compliant
Note: Permanent device damage may occur if the Absolute Maximum Ratings are exceeded. Functional operation should be
restricted to the conditions as specified in the operation sections of this data sheet. Exposure to absolute maximum
rating conditions for extended periods of time may affect device reliability.
Rev. 1.0
13
Si5315
2. Typical Application Circuit
C4 1 µF
System
Power
Supply
C3 0.1 µF
Ferrite
Bead
C2 0.1 µF
VDD = 3.3 V
CKIN1–
82 
GND Pad
CKIN1+
GND
130 
VDD
130 
C1 0.1 µF
0.1 µF
CKOUT1+
+
100 
CKOUT1–
82 
–
0.1 µF
0.1 µF
Clock Outputs to
Ethernet PHYs
CKOUT2+
Backplane or Line
Recovered Clock
Inputs
+
100 
VDD = 3.3 V
CKOUT2–
130 
–
0.1 µF
130 
CKIN2+
CKIN2–
82 
82 
Option 1:
LOS1
CKIN1 Loss of Signal Indicator
LOS2
CKIN2 Loss of Signal Indicator
LOL
XA
PLL Loss of Lock Indicator
40 MHz Crystal
XB
Si5315
0.1 µF
Option 2:
Ext. Refclk+
XA
0.1 µF
Ext. Refclk–
XB
VDD
15 k
XTAL/Clock2
Crystal/Ref Clk
VDD
Manual/Automatic Clock 15 k
Selection (L)
15 k
AUTOSEL2
VDD
15 k
15 k
CS3
Input Clock Select
VDD
15 k
15 k
FRQTBL2
Frequency Table Select
VDD
15 k
15 k
FRQSEL[3:0]2
Frequency Select
VDD
15 k
15 k
BWSEL[1:0]2
Bandwidth Select
VDD
15 k
15 k
SFOUT[1:0]2
Signal Format Select
VDD
Clock Output 2 Disable/ 15 k
Bypass Mode Control
15 k
DBL2_BY2
15 k
Reset
RST
Notes: 1. Assumes differential LVPECL termination (3.3 V) on clock inputs.
2. Denotes tri-level input pins with states designated as L (ground), M (VDD/2), and H (VDD).
3. Assumes manual input clock selection.
Figure 5. Si5315 Typical Application Circuit
14
Rev. 1.0
Si5315
3. System Level Overview
The Si5315 provides clock translation, jitter attenuation, and clock distribution for high-performance Synchronous
Ethernet* line card timing applications.
*Note: The Si5315 supports SyncE EEC options 1 and 2 when paired with a timing card that implements the required wander
filtering and Stratum 3 compliant reference clock. For detailed information, refer to “AN420: SyncE and IEEE 1588: Sync
Distribution for a Unified Network”.
The Si5315 provides clock translation, jitter attenuation, and clock distribution for high-performance Synchronous
Ethernet line card timing applications. The device accepts two clock inputs ranging from 8 kHz to 644.53 MHz and
generates two equal frequency, low jitter clock outputs ranging from 8 kHz to 644.53 MHz. For ease of use, the
Si5315 is pin controlled to enable simple device configuration of frequency plans, PLL loop bandwidth, and input
clock selection. The DSPLL locks to one of two input reference clocks and provides over 200 frequency
translations to synchronize output clocks for Ethernet, SONET/SDH, and PDH line cards. The Si5315 implements
internal state machines to control hitless switching between input clocks and holdover. Status alarms, loss of signal
(LOS) and loss of lock (LOL) are provided on output pins to indicate a change in device status.
This device is designed for systems with line cards that are synchronized to a redundant, centralized telecom or
Ethernet backplane. The Si5315 synchronizes to backplane clocks and generates a multiplied, jitter attenuated
Ethernet/SONET/SDH clock or PDH clock. A typical system application is shown in Figure 6. The Si5315
translates a 19.44 MHz clock from the telecom backplane to an Ethernet or SONET/SDH clock frequency to the
PHY and filters the jitter to ensure compliance with related ITU-T and Telcordia standards.
Telecom
or
Ethernet
Backplane
Redundant
Timing Cards
10G LAN / WAN
SyncE Line Card
Tx Timing Path
Wander Filtering
Hitless Switching
Holdover
BITS A
BITS B
Hitless Switching
Jitter Filtering
Frequency Translation
A
Network
Network Sync
Synchronization
PLL
10GbE
PHY
B
A
Si5315
B
155.52 MHz
156.25 MHz
161.1328125 MHz
8 kHz
19.44 MHz
25 MHz
10GbE
PHY
Rx Timing Path
Line
Recovered
Clocks
8 kHz
19.44 MHz
25 MHz
Line Recovered Timing
Multi-Port
SONET / SDH / PDH Line Card
Tx Timing Path
Hitless Switching
Jitter Filtering
Frequency Translation
OC-3 / 12
77.76 / 155.52 MHz
A
Si5315
B
1.544 / 2.048 MHz
T1 / E1
Rx Timing Path
8 kHz
19.44 MHz
25 MHz
Line
Recovered
Clocks
Figure 6. Typical Si5315 Application
Rev. 1.0
15
Si5315
4. Functional Description
Crystal or
Reference Clock
Xtal/Clock
XA
XB
PLL Bypass
0
CKIN1+
CKIN1–
2
CKIN2+
CKIN2–
2
2
0
f3
DSPLL®
fOSC
CKOUT1+
CKOUT1–
1
SFOUT[1:0]
1
0
2
CKOUT2+
CKOUT2–
1
LOS1
LOS2
LOL
AUTOSEL
DBL2_BY
Signal Detect
Control
CS/CA
RST
BWSEL[1:0]
FRQSEL[3:0]
FRQTBL
Bandwidth
Control
VDD (1.8, 2.5, or 3.3 V)
Frequency
Control
GND
Figure 7. Detailed Block Diagram
4.1. Overview
The Si5315 is a jitter-attenuating precision clock multiplier for Synchronous Ethernet, SONET/SDH, and PDH
(T1/E1) applications. The Si5315 accepts dual clock inputs ranging from 8 kHz to 644.53 MHz and generates two
frequency-multiplied clock outputs ranging from 8 kHz to 644.53 MHz. The two input clocks are at the same
frequency and the two output clocks are at the same frequency. The input clock frequency and clock multiplication
ratio are selectable from a look up table of popular SyncE and T1/E1 rates.
The Si5315 is based on Silicon Laboratories' 3rd-generation DSPLL® technology, which provides any-frequency
synthesis and jitter attenuation in a highly integrated PLL solution that eliminates the need for external VCXO and
loop filter components. The Si5315 PLL loop bandwidth is selectable via the BWSEL[1:0] pins and supports a
range from 60 to 8.4 kHz.
The Si5315 supports hitless switching between the two input clocks in compliance with ITU-T G.8262 and Telcordia
GR-253-CORE and GR-1244-CORE. This feature greatly minimizes the propagation of phase transients to the
clock outputs during an input clock transition (<200 ps typ). Manual and automatic revertive and non-revertive input
clock switching options are available via the AUTOSEL input pin. The Si5315 monitors both input clocks for loss-ofsignal and provides a LOS alarm when it detects missing pulses on either input clock. The device monitors the lock
status of the PLL. The lock detect algorithm works by continuously monitoring the phase of the input clock in
relation to the phase of the feedback clock. The Si5315 provides a holdover capability that allows the device to
continue generation of a stable output clock when the selected input reference is lost.
The Si5315 has two differential clock outputs. The signal format of the clock outputs is programmable to support
LVPECL, LVDS, CML, or CMOS loads. The second clock output can be powered down to minimize power
consumption. For system-level debugging, a bypass mode is available which drives the output clock directly from
the input clock, bypassing the internal DSPLL. The device operates from a single 1.8, 2.5, or 3.3 V supply.
16
Rev. 1.0
Si5315
4.2. PLL Performance
The Si5315 provides extremely low jitter generation, a well-controlled jitter transfer function, and high jitter
tolerance due to the high level of integration.
4.2.1. Jitter Generation
Jitter generation is defined as the amount of jitter produced at the output of the device with a jitter free input clock.
Generated jitter arises from sources within the VCO and other PLL components. Jitter generation is a function of
the PLL bandwidth setting. Higher loop bandwidth settings may result in lower jitter generation, but may result in
less attenuation of jitter that might be present on the input clock signal.
4.2.2. Jitter Transfer
Jitter transfer is defined as the ratio of output signal jitter to input signal jitter for a specified jitter frequency. The
jitter transfer characteristic determines the amount of input clock jitter that passes to the outputs. The DSPLL
technology used in the Si5315 provides tightly controlled jitter transfer curves because the PLL gain parameters
are determined largely by digital circuits which do not vary over supply voltage, process, and temperature. In a
system application, a well-controlled transfer curve minimizes the output clock jitter variation from board to board
and provides more consistent system level jitter performance.
The jitter transfer characteristic is a function of the loop bandwidth setting. Lower bandwidth settings result in more
jitter attenuation of the incoming clock, but may result in higher jitter generation. Figure 8 shows the jitter transfer
curve mask.
Jitter
Transfer
Jitter Out
Jitter In
0 dB
Peaking
–20 dB/dec.
BW
fJitter
Figure 8. PLL Jitter Transfer Mask/Template
Rev. 1.0
17
Si5315
4.2.3. Jitter Tolerance
Jitter tolerance is defined as the maximum peak-to-peak sinusoidal jitter that can be present on the incoming clock
before the DSPLL loses lock. The tolerance is a function of the jitter frequency, because tolerance improves for
lower input jitter frequency.
The jitter tolerance of the DSPLL is a function of the loop bandwidth setting. Figure 9 shows the general shape of
the jitter tolerance curve versus input jitter frequency. For jitter frequencies above the loop bandwidth, the tolerance
is a constant value Aj0. Beginning at the PLL bandwidth, the tolerance increases at a rate of 20 dB/decade for
lower input jitter frequencies.
Input
Jitter
Amplitude
–20 dB/dec.
Excessive Input Jitter Range
Aj0
BW/100 BW/10
BW
fJitter In
Figure 9. Jitter Tolerance Mask/Template
The equation for the high frequency jitter tolerance can be expressed as a function of the PLL loop bandwidth
(i.e., BW):
5000
A j0 = ------------- ns pk-pk
BW
For example, the jitter tolerance when fin = 19.44 MHz, fout = 161.13 MHz and the loop bandwidth (BW) is 113 Hz:
5000
A j0 = ------------- = 44.24 ns pk-pk
113
4.2.4. Jitter Attenuation Performance
The Internal VCO uses the reference clock on the XA/XB pins as its reference for jitter attenuation. The XA/XB pins
support either a crystal input or an input buffer single-ended or differential clock input, such that an external
oscillator can become the reference source. In either case, the device accepts a wide margin in absolute frequency
of the reference input. (See 5.5. "Holdover Mode" on page 32.) In holdover, the Si5315's output clock stability
matches the reference supplied on the XA/XB pins. The external crystal or reference clock must be selected based
on the stability requirements of the application if holdover is a key requirement.
However, care must be exercised in certain areas for optimum performance. For examples of connections to the
XA/XB pins, refer to 7. "Crystal/Reference Clock Input" on page 38.
18
Rev. 1.0
Si5315
5. Frequency Plan Tables
For ease of use, the Si5315 is pin controlled to enable simple device configuration of the frequency plan and PLL
loop bandwidth via a predefined look up table. The DSPLL has been optimized for each frequency multiplication
and PLL loop bandwidth provided in Table 9 on page 20.
Many of the control inputs are three levels: High, Low, and Medium. High and Low are standard voltage levels
determined by the supply voltage: VDD and Ground. If the input pin is left floating, it is driven to nominally half of
VDD. Effectively, this creates three logic levels for these controls. See 1.2. "Three-Level (3L) Input Pins (With
External Resistors)" on page 12 and 8. "Power Supply Filtering" on page 41 for additional information.
5.1. Frequency Multiplication Plan
The input to output clock multiplication is set by the 3-level FRQSEL[3:0] pins. The device provides a wide range of
commonly used SyncE, SONET/SDH, and PDH frequency translations. The CKIN1 and CKIN2 inputs must be the
same frequency as specified in Table 9. Both CKOUT1 and CKOUT2 outputs are at the same frequency.
5.1.1. PLL Loop Bandwidth Plan
The Si5315's loop bandwidth ranges from 60 Hz to 8.4 kHz. For each frequency multiplication, its corresponding
loop bandwidth is provided in a simple look up table. (See Table 9 on page 20.) The loop bandwidth (BW) is
digitally programmable using the 3-level BWSEL [1:0] and FRQTBL input pins.
Rev. 1.0
19
20
Rev. 1.0
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
1.544
1.544
1.544
1.544
1.544
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
19.44
8.192
2.048
1.544
0.008
622.08
312.5
311.04
156.25
155.52
125
77.76
65.536
51.84
44.736
38.88
34.368
32.768
25
19.44
8.192
2.048
1.544
L
L
L
L
L
H
H
H
H
H
M
M
M
M
M
M
M
L
L
L
L
L
L
L
FRQTBL
LMLH
LMLM
LMLL
LLHH
LLHM
LLMM
LLML
LLLH
LLLM
LLLL
LLHL
LLMH
LLMM
LLML
LLLH
LLLM
LLLL
LLHL
LLMH
LLMM
LLML
LLLH
LLLM
LLLL
FRQSEL
[3:0]
257
257
257
—
257
257
257
257
257
257
257
257
257
257
257
257
257
257
257
257
257
257
257
257
LM
60
60
60
—
60
60
60
60
60
60
60
60
—
60
60
60
60
60
60
60
60
60
60
60
LH
—
—
—
6047
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
ML
—
—
—
1451
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
MM
—
—
—
359
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
MH
—
—
—
179
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
HL
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
0.008
2
0.008
(MHz)
(MHz)
0.008
fOUT
fIN
1
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings
—
—
—
89
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
HH
Si5315
Rev. 1.0
1.544
1.544
1.544
1.544
1.544
1.544
1.544
1.544
1.544
1.544
1.544
1.544
2.048
2.048
2.048
2.048
2.048
2.048
2.048
2.048
2.048
2.048
2.048
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
51.84
44.736
38.88
34.368
32.768
25
19.44
8.192
2.048
1.544
0.008
622.08
312.5
311.04
156.25
155.52
125
77.76
65.536
51.84
44.736
38.88
34.368
32.768
M
M
M
M
L
L
L
L
L
L
L
H
H
H
H
H
M
M
M
M
M
M
M
L
L
FRQTBL
LMHH
LMHM
LMHL
LMMH
LHLH
LHLM
LHLL
LMHH
LMHM
LMHL
LMMH
LMLL
LLHH
LLHM
LLHL
LLMH
LMMM
LMML
LMLH
LMLM
LMLL
LLHH
LLHM
LMMM
LMML
FRQSEL
[3:0]
—
—
—
—
—
2087
—
—
—
1037
2089
257
257
257
257
257
257
257
257
257
257
257
257
257
257
LM
—
3983
—
8163
—
485
—
—
—
242
485
60
60
60
60
60
60
60
—
60
60
60
60
60
60
LH
3946
1944
3946
3935
3947
240
3946
3949
3949
119
240
—
—
—
—
—
—
—
—
—
—
—
—
—
—
ML
958
477
958
958
959
—
958
959
959
—
59
—
—
—
—
—
—
—
—
—
—
—
—
—
—
MM
59
118
238
118
118
118
—
118
118
118
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
HL
118
238
238
238
—
238
238
238
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
1.544
26
25
(MHz)
(MHz)
1.544
fOUT
fIN
25
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
59
—
59
—
59
—
59
59
59
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
HH
Si5315
21
22
Rev. 1.0
2.048
2.048
2.048
2.048
2.048
2.048
8.192
8.192
8.192
8.192
8.192
8.192
8.192
8.192
8.192
8.192
8.192
8.192
8.192
8.192
19.44
19.44
19.44
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
2.048
1.544
0.008
125
77.76
65.536
51.84
44.736
38.88
34.368
32.768
25
19.44
8.192
2.048
1.544
0.008
622.08
312.5
311.04
156.25
155.52
125
77.76
L
L
L
M
M
M
M
M
M
M
L
L
L
L
L
L
L
H
H
H
H
H
M
M
M
FRQTBL
MLML
MLLH
MLLM
MLLL
LHHH
LHHM
LHHL
LHMH
LHMM
LHML
MLLL
LHHH
LHHM
LHHL
LHMH
LHMM
LHML
LMMH
LMMM
LMML
LMLH
LMLM
LHLH
LHLM
LHLL
FRQSEL
[3:0]
—
—
1759
1037
—
—
—
—
—
—
—
2087
—
—
—
1037
2089
—
1037
—
1037
—
1037
—
—
LM
3348
2779
409
242
—
—
—
3983
—
8163
—
485
—
—
—
242
485
—
242
—
242
—
242
—
8185
LH
1638
1362
202
119
3946
6411
3946
1944
3946
3935
6431
240
3946
6434
6434
119
240
3946
119
3946
119
3946
119
3946
3940
ML
402
335
—
—
958
1539
958
477
958
958
1541
—
958
1541
1541
—
59
958
—
958
—
958
—
958
958
MM
—
—
100
—
—
118
190
118
59
118
118
190
—
118
190
190
—
—
118
—
118
—
118
—
118
118
HL
83
—
—
238
381
238
118
238
238
381
—
238
381
381
—
—
238
—
238
—
238
—
238
238
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
2.048
51
65.536
(MHz)
(MHz)
2.048
fOUT
fIN
50
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
—
—
—
—
59
95
59
—
59
—
95
—
59
95
95
—
—
59
—
59
—
59
—
59
—
HH
Si5315
Rev. 1.0
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
19.44
25
25
25
25
25
25
25
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
32.768
25
19.44
8.192
2.048
1.544
0.008
644.5313
622.08
312.5
311.04
161.1328
156.25
155.52
125
77.76
65.536
51.84
44.736
38.88
34.368
32.768
25
19.44
L
L
L
L
L
L
L
H
H
H
H
H
H
H
M
M
M
M
M
M
M
L
L
L
L
FRQTBL
MMMH
MMMM
MMML
MMLH
MMLM
MMLL
MLHH
LHML
LHLH
LHLM
LHLL
LMHH
LMHM
LMHL
MLHM
MLHL
MLMH
MLMM
MLML
MLLH
MLLM
MLHM
MLHL
MLMH
MLMM
FRQSEL
[3:0]
6737
—
—
6737
1299
6741
—
103
—
6003
—
484
6003
—
3960
—
2618
—
—
—
—
—
—
—
—
LM
1529
—
—
1529
303
1529
—
—
—
1373
—
113
1373
—
913
—
607
—
5653
—
5662
—
2778
—
3348
LH
753
7615
6551
753
150
753
7045
—
7696
677
7696
—
677
7696
450
7696
300
7696
2747
7703
2749
5022
1362
7706
1638
ML
186
1812
1568
186
—
186
1681
—
1832
167
1832
—
167
1832
111
1832
74
1832
672
1832
672
1215
335
1832
402
MM
223
—
—
193
—
—
—
207
—
225
—
225
—
—
225
—
225
—
225
83
225
83
150
—
225
—
HL
447
387
—
—
—
415
—
452
—
452
—
—
452
—
452
—
452
167
452
167
301
83
452
100
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
19.44
76
8.192
(MHz)
(MHz)
19.44
fOUT
fIN
75
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
—
111
96
—
—
—
103
—
112
—
112
—
—
112
—
112
—
112
—
112
—
75
—
112
—
HH
Si5315
23
24
Rev. 1.0
25
25
25
25
25
25
25
25
25
25
25
25
25
32.768
32.768
32.768
32.768
32.768
32.768
32.768
32.768
32.768
32.768
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
44.736
38.88
34.368
32.768
25
19.44
8.192
2.048
1.544
0.008
644.5313
622.08
312.5
311.04
161.1328
156.25
155.52
125
77.76
65.536
51.84
50
44.736
38.88
M
M
M
L
L
L
L
L
L
L
H
H
H
H
H
H
H
M
M
M
M
H
M
M
M
FRQTBL
MMHH
MMHM
MMHL
MHML
MHLH
MHLM
MHLL
MMHH
MMHM
MMHL
MLLM
MLLL
LHHH
LHHM
LHHL
LHMH
LHMM
MMMH
MMMM
MMML
MMLH
HMLH
MMLM
MMLL
MLHH
FRQSEL
[3:0]
—
—
—
—
2087
—
—
—
1037
2089
—
1298
—
1298
—
—
1298
—
6706
1298
—
—
1298
6729
6722
LM
3983
—
8163
—
485
—
—
—
242
485
—
303
—
303
—
—
303
—
1528
303
7988
—
303
1529
1528
LH
1944
—
3935
7632
240
3946
7632
7187
119
240
6106
150
7606
150
6106
7606
150
7606
753
150
3846
7880
150
753
753
ML
477
958
958
1816
—
958
1816
1714
—
59
1468
—
1811
—
1468
1811
—
1811
186
—
936
1880
—
186
186
MM
118
59
118
118
223
—
118
223
211
—
—
181
—
223
—
181
223
—
223
—
—
116
230
—
—
—
HL
238
238
448
—
238
448
423
—
—
363
—
447
—
363
447
—
447
—
—
232
470
—
—
—
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
25
101
34.368
(MHz)
(MHz)
25
fOUT
fIN
100
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
—
59
—
111
—
59
111
105
—
—
90
—
111
—
90
111
—
111
—
—
—
120
—
—
—
HH
Si5315
Rev. 1.0
32.768
32.768
50
50
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
77.76
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
644.5313
622.08
312.5
311.04
161.1328
156.25
155.52
125
77.76
65.536
51.84
44.736
38.88
34.368
25
19.44
2.048
1.544
0.008
50
25
125
77.76
65.536
H
H
H
H
H
H
H
M
M
M
M
M
M
M
L
L
L
L
L
M
L
M
M
M
M
FRQTBL
MLHH
MLHM
MLHL
MLMH
MLMM
MLML
MLLH
HLLM
HLLL
MHHH
MHHM
MHHL
MHMH
MHMM
MHHH
MHHM
MHHL
MHMH
MHMM
HMLH
HHHH
MHML
MHLH
MHLM
MHLL
FRQSEL
[3:0]
484
—
6003
—
484
6003
—
5336
—
—
—
—
—
—
—
—
—
—
2089
—
—
1037
—
—
—
LM
113
—
1373
—
113
1373
—
1220
—
2461
—
—
—
—
2778
—
—
2779
485
—
—
242
—
—
—
LH
—
7905
677
7905
—
677
7905
602
7905
1208
7905
6756
7905
6798
1362
7905
6804
1362
240
7770
7880
119
3946
7604
3946
ML
—
1879
167
1879
—
167
1879
148
1879
298
1879
1623
1879
1626
335
1879
1626
335
59
1850
1880
—
958
1815
958
MM
231
—
—
—
231
—
—
231
—
231
—
231
200
231
200
—
231
200
—
—
230
230
—
118
223
118
HL
464
—
464
—
—
464
—
464
74
464
402
464
402
83
464
402
83
—
466
470
—
238
448
238
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
32.768
126
51.84
(MHz)
(MHz)
32.768
fOUT
fIN
125
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
—
115
—
115
—
—
115
—
115
—
115
100
115
100
—
115
100
—
—
110
120
—
59
111
59
HH
Si5315
25
26
Rev. 1.0
125
125
125
125
125
125
125
125
125
125
125
125
125
125
125
125
125
155.52
155.52
155.52
155.52
155.52
155.52
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
77.76
25
19.44
2.048
1.544
0.008
644.5313
622.08
312.5
311.04
161.1328
156.25
155.52
125
77.76
65.536
51.84
44.736
38.88
34.368
25
19.44
2.048
1.544
H
L
L
L
L
L
H
H
H
H
H
H
H
M
M
M
M
M
M
M
L
L
L
L
L
FRQTBL
MMHM
HMLL
HLHH
HLHM
HLHL
HLMH
MMHL
MMMH
MMMM
MMML
MMLH
MMLM
MMLL
HLHH
HLHM
HLHL
HLMH
HLMM
HLML
HLLH
HLMM
HLML
HLLH
HLLM
HLLL
FRQSEL
[3:0]
—
—
—
—
—
2089
—
1298
—
1298
—
—
1298
—
6706
1298
—
1298
6729
6722
—
—
1299
6741
—
LM
—
2778
—
—
2779
485
—
303
—
303
—
—
303
—
1528
303
7988
303
1529
1528
—
—
303
1529
—
LH
7905
1362
7905
7606
1362
240
7718
150
7862
150
7718
7862
150
7862
753
150
3846
150
753
753
7862
6551
150
753
7045
ML
1879
335
1879
1809
335
59
1839
—
1870
—
1839
1870
—
1870
186
—
936
—
186
186
1870
1568
—
186
1681
MM
—
231
464
231
223
—
—
226
—
230
—
226
230
—
230
—
—
116
—
—
—
230
193
—
—
207
HL
83
464
447
83
—
454
—
462
—
454
462
—
462
—
—
232
—
—
—
462
387
—
—
415
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
125
151
0.008
(MHz)
(MHz)
125
fOUT
fIN
150
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
115
—
115
111
—
—
113
—
115
—
113
115
—
115
—
—
—
—
—
—
115
96
—
—
103
HH
Si5315
Rev. 1.0
155.52
155.52
155.52
155.52
155.52
155.52
156.25
156.25
156.25
156.25
156.25
156.25
156.25
156.25
156.25
156.25
156.25
156.25
156.25
156.25
161.1328
161.1328
161.1328
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
2.048
1.544
0.008
644.5313
622.08
312.5
311.04
161.1328
156.25
155.52
125
77.76
25
19.44
2.048
1.544
0.008
644.5313
622.08
312.5
311.04
161.1328
156.25
155.52
L
L
L
H
H
H
H
H
H
H
H
H
L
L
L
L
L
H
H
H
H
H
H
H
H
FRQTBL
HMHH
HMHM
HMHL
HLHL
HLMH
HLMM
HLML
HLLH
HLLM
HLLL
MHHH
MHHM
HMMH
HMMM
HMML
HMLH
HMLM
MHHL
MHMH
MHMM
MHML
MHLH
MHLM
MHLL
MMHH
FRQSEL
[3:0]
225
151
225
—
322
—
322
—
—
322
—
1625
—
—
322
1627
—
828
—
6003
—
484
6003
—
5336
LM
—
—
—
—
75
—
75
—
—
75
—
379
—
—
75
379
—
193
—
1373
—
113
1373
—
1220
LH
—
—
—
7718
—
7835
—
7718
7835
—
7835
187
7835
4852
—
187
6123
95
7905
677
7905
—
677
7905
602
ML
—
—
—
1839
—
1864
—
1839
1864
—
1864
—
1864
1172
—
—
1469
—
1879
167
1879
—
167
1879
148
MM
—
—
—
—
226
—
229
—
226
229
—
229
—
229
145
—
—
181
—
231
—
231
—
—
231
—
HL
—
—
454
—
460
—
454
460
—
460
—
460
290
—
—
363
—
464
—
464
—
—
464
—
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
155.52
176
125
(MHz)
(MHz)
155.52
fOUT
fIN
175
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
—
—
—
113
—
114
—
113
114
—
114
—
114
72
—
—
90
—
115
—
115
—
—
115
—
HH
Si5315
27
28
161.1328
161.1328
161.1328
161.1328 161.1328
161.1328
161.1328 644.5313
644.5313
644.5313
644.5313
644.5313
644.5313
644.5313
644.5313
644.5313
644.5313
644.5313 161.1328
644.5313
644.5313
644.5313
644.5313 644.5313
202
203
204
205
206
207
208
209
210
211
212
213
214
Rev. 1.0
215
216
217
218
219
220
221
H
H
H
H
H
H
H
H
H
L
L
L
L
L
H
H
H
H
H
H
L
L
FRQTBL
HHMM
HHML
HHLH
HHLM
HHLL
HMHH
HMHM
HMHL
HMMH
HHHL
HHMH
HHMM
HHML
HHLH
HMMM
HMML
HMLM
HMLL
HLHH
HLHM
HHLM
HHLL
FRQSEL
[3:0]
—
120
206
828
—
—
828
—
828
—
—
—
413
880
151
3873
332
—
—
678
678
679
LM
—
—
—
193
—
—
193
—
193
—
3641
3373
96
206
—
892
78
—
—
159
159
159
LH
7895
—
—
95
7895
7732
95
7732
95
7886
1779
1650
—
101
—
440
—
7019
7179
78
78
78
ML
1880
—
—
—
1880
1840
—
1840
—
1875
437
405
—
—
—
109
—
1683
1721
—
—
—
MM
—
231
464
—
—
231
226
—
226
—
231
—
—
—
—
—
—
—
207
212
—
—
—
HL
—
—
—
464
454
—
454
—
463
108
101
—
—
—
—
—
416
426
—
—
—
MH
Loop Bandwidth Selection (Hz), BWSEL[1:0]
Notes:
1. FIN and FOUT frequency values may be rounded off. For exact multiplication ratios, please contact Silicon Labs.
2. Si5315A supports all frequency plans.
3. Si5315B supports output frequency plans up to 125 MHz.
622.08
312.5
311.04
156.25
155.52
125
77.76
25
19.44
2.048
1.544
0.008
312.5
156.25
125
77.76
25
161.1328
201
19.44
(MHz)
(MHz)
161.1328
fOUT
fIN
200
Plan #
Table 9. Look Up Tables for Clock Multiplication and Loop Bandwidth Settings (Continued)
115
—
—
—
115
113
—
113
—
115
—
—
—
—
—
—
—
103
106
—
—
—
HH
Si5315
Si5315
5.2. PLL Self-Calibration
An internal self-calibration (ICAL) is performed before operation to optimize loop parameters and jitter
performance. While the self-calibration is being performed, the DSPLL is being internally controlled by the selfcalibration state machine. The LOL alarm will be active during ICAL. The self-calibration time tLOCKHW is given in
Table 3, “AC Characteristics”.
Any of the following events will trigger a self-calibration:

Power-on-reset (POR)
 Release of the external reset pin RST (transition of RST from 0 to 1)
 Change in FRQSEL, FRQTBL, BWSEL, or XTAL/CLOCK pins
 Internal DSPLL registers out-of-range, indicating the need to relock the DSPLL
In any of the above cases, an internal self-calibration will be initiated if a valid input clock exists (no input alarm)
and is selected as the active clock at that time. The external crystal or reference clock must also be present for the
self-calibration to begin. If valid clocks are not present, the self-calibration state machine will wait until they appear,
at which time the calibration will start. An output clock will be active while waiting for a valid input clock. The output
clock frequency is based on the VCO range determine by FRQSEL and FRQTBL settings. This output clock will
vary by ±20%. If no output clock is desired prior to an ICAL, then the SFOUT pins should be kept at LM for
1.2 seconds until the output clock is stable.
After a successful self-calibration has been performed with a valid input clock, no subsequent self calibrations are
performed unless one of the above conditions are met. If the input clock is lost following self-calibration, the device
enters holdover mode. When the input clock returns, the device relocks to the input clock without performing a selfcalibration.
5.2.1. Input Clock Stability during Internal Self-Calibration
An exit from reset must occur when the selected CKINn clock is stable in frequency with a frequency value that is
within the device operating range. The other CKINs must also either be stable in frequency or squelched during a
reset.
5.2.2. Self-Calibration caused by Changes in Input Frequency
If the selected CKINn varies by 500 ppm or more in frequency since the last calibration, the device may initiate a
self-calibration.
5.2.3. Device Reset
Upon powerup, the device internally executes a power-on-reset (POR) which resets the internal device logic. The
pin RST can also be used to initiate a reset. The device stays in this state until a valid CKINn is present, when it
then performs a PLL Self-Calibration (See 5.2. "PLL Self-Calibration”).
5.2.4. Recommended Reset Guidelines
Follow the recommended RESET guidelines in Table 10 when reset should be applied to a device.
Table 10. Si5315 Pins and Reset
Pin #
Si5315 Pin Name
Must Reset after Changing
2
FRQTBL
Yes
11
XTAL/CLOCK
Yes
22
BWSEL0
Yes
23
BWSEL1
Yes
24
FRQSEL0
Yes
25
FRQSEL1
Yes
26
FRQSEL2
Yes
27
FRQSEL3
Yes
Rev. 1.0
29
Si5315
5.2.5. Hitless Switching with Phase Build-Out
Silicon Laboratories switching technology performs "phase build-out" to minimize the propagation of phase
transients to the clock outputs during input clock switching. All switching between input clocks occurs within the
input multiplexor and phase detector circuitry. The phase detector circuitry continually monitors the phase
difference between each input clock and the DSPLL output clock, fOSC. The phase detector circuitry can lock to a
clock signal at a specified phase offset relative to fOSC so that the phase offset is maintained by the PLL circuitry.
At the time a clock switch occurs, the phase detector circuitry knows both the input-to-output phase relationship for
the original input clock and for the new input clock. The phase detector circuitry locks to the new input clock at the
new clock's phase offset so that the phase of the output clock is not disturbed. The phase difference between the
two input clocks is absorbed in the phase detector's offset value, rather than being propagated to the clock output.
The switching technology virtually eliminates the output clock phase transients traditionally associated with clock
rearrangement (input clock switching). The Maximum Time Interval Error (MTIE) and maximum slope for clock
output phase transients during clock switching are given in (Table 3, “AC Characteristics”). These values fall
significantly below the limits specified in the ITU-T G.8262, Telcordia GR-1244-CORE, and GR-253-CORE
requirements.
5.3. Input Clock Control
This section describes the clock selection capabilities (manual input selection, automatic input selection, hitless
switching, and revertive switching). When switching between two clocks, LOL may temporarily go high if the two
clocks differ in frequency by more than 100 ppm.
5.3.1. Manual Clock Selection
Manual control of input clock selection is chosen via the CS_CA pin according to Table 11 and Table 12.
Table 11. Automatic/Manual Clock Selection
AUTOSEL
Clock Selection Mode
L
Manual
M
Automatic non-revertive
H
Automatic revertive
Table 12. Manual Input Clock Selection, AUTOSEL = L
CS_CA
Si5315
AUTOSEL = L
0
CKIN1
1
CKIN2
5.3.2. Automatic Clock Selection
The AUTOSEL input pin sets the input clock selection mode as shown in Table 11. Automatic switching is either
revertive or non-revertive. Setting AUTOSEL to M or H, changes the CS_CA pin to an output pin that indicates the
state of the automatic clock selection.
Table 13. Clock Active Indicators, AUTOSEL = M or H
30
CS_CA
Active Clock
0
CKIN1
1
CKIN2
Rev. 1.0
Si5315
The prioritization of clock inputs for automatic switching is shown in Table 14. This priority is hardwired in the
devices.
Table 14. Input Clock Priority for Auto Switching
Priority
Input Clocks
1
CKIN1
2
CKIN2
3
Holdover
At power-on or reset, the valid CKINn with the highest priority (1 being the highest priority) is automatically
selected. If no valid CKINn is available, the device suppresses the output clocks and waits for a valid CKINn signal.
If the currently selected CKINn goes into an alarm state, the next valid CKINn in priority order is selected. If no valid
CKINn is available, the device enters holdover.
Operation in revertive and non- revertive is different when a signal becomes valid:
Revertive (AUTOSEL = H):
The device constantly monitors all CKINn. If a CKINn with a higher priority than
the current active CKINn becomes valid, the active CKINn is changed to the
CKINn with the highest priority.
Non-revertive (AUTOSEL = M): The active clock does not change until there is an alarm on the active clock. The
device will then select the highest priority CKINn that is valid. Once in holdover,
the device will switch to the first CKINn that becomes valid.
5.4. Alarms
Summary alarms are available to indicate the overall status of the input signals. Alarm outputs stay high until all the
alarm conditions for that alarm output are cleared.
5.4.1. Loss-of-Signal
The device has loss-of-signal circuitry that continuously monitors CKINn for missing pulses. The LOS circuitry
generates an internal LOSn_INT output signal that is processed with other alarms to generate LOS1 and LOS2.
An LOS condition on CKIN1 causes the internal LOS1_INT alarm to become active. Similarly, an LOS condition on
CKINn causes the LOSn_INT alarm to become active. Once a LOSn_INT alarm is asserted on one of the input
clocks, it remains asserted until that input clock is validated over a designated time period. The time to clear
LOSn_INT after a valid input clock appears is listed in Table 3, “AC Characteristics”. If another error condition on
the same input clock is detected during the validation time then the alarm remains asserted and the validation time
starts over.
5.4.1.1. LOS Algorithm
The LOS circuitry divides down each input clock to produce an 8 kHz to 2 MHz signal. The LOS circuitry over
samples this divided down input clock using a 40 MHz clock to search for extended periods of time without input
clock transitions. If the LOS monitor detects twice the normal number of samples without a clock edge, a
LOSn_INT alarm is declared. Table 3, “AC Characteristics” gives the minimum and maximum amount of time for
the LOS monitor to trigger.
5.4.1.2. Lock Detect
The PLL lock detection algorithm indicates the lock status on the LOL output pin. The algorithm works by
continuously monitoring the phase of the input clock in relation to the phase of the feedback clock. If the time
between two consecutive phase cycle slips is greater than the retrigger time, the PLL is in lock. The LOL output
has a guaranteed minimum pulse width as shown in (Table 3, “AC Characteristics”). The LOL pin is also held in the
active state during an internal PLL calibration. The retrigger time is automatically set based on the PLL closed loop
bandwidth (See Table 15).
Rev. 1.0
31
Si5315
Table 15. Lock Detect Retrigger Time
PLL Bandwidth Setting (BW)
Retrigger Time (ms)
60–120 Hz
53
120–240 Hz
26.5
240–480 Hz
13.3
480–960 Hz
6.6
960–1920 Hz
3.3
1920–3840 Hz
1.66
3840–7680 Hz
0.833
5.5. Holdover Mode
If an LOS condition exists on the selected input clock, the device enters holdover. In this mode, the device provides
a stable output frequency until the input clock returns and is validated. When the device enters holdover, the
internal oscillator is initially held to its last frequency value. Next, the internal oscillator slowly transitions to a
historical average frequency value that was taken over a time window of 6,711 ms in size that ended 26 ms before
the device entered holdover. This frequency value is taken from an internal memory location that keeps a record of
previous DSPLL frequency values. By using a historical average frequency, input clock phase and frequency
transients that may occur immediately preceding loss of clock or any event causing holdover do not affect the
holdover frequency. Also, noise related to input clock jitter or internal PLL jitter is minimized.
If a highly stable reference, such as an oven-controlled crystal oscillator, is supplied at XA/XB, an extremely stable
holdover can be achieved. If a crystal is supplied at the XA/XB port, the holdover stability will be limited by the
stability of the crystal; Table 3, “AC Characteristics” gives the specifications related to the holdover function.
5.5.1. Recovery from Holdover
When the input clock signal returns, the device transitions from holdover to the selected input clock. The device
performs hitless recovery from holdover. The clock transition from holdover to the returned input clock includes
"phase buildout" to absorb the phase difference between the holdover clock phase and the input clock phase. See
Table 3, “AC Characteristics” for specifications.
5.6. PLL Bypass Mode
The Si5315 supports a PLL bypass mode in which the selected input clock is fed directly to both enabled output
buffers, bypassing the DSPLL. Internally, the bypass path is implemented with high-speed differential signaling;
however, this path is not a low jitter path and will see significantly higher jitter on CKOUT. In PLL bypass mode, the
input and output clocks will be at the same frequency. PLL bypass mode is useful in a laboratory environment to
measure system performance with and without the jitter attenuation provided by the DSPLL. The DSBL2_BY pin is
used to select the PLL Bypass Mode according to Table 16. Bypass mode is not supported for CMOS clock outputs
(SFOUT = LH).
Table 16. DSBL2/BYPASS Pin Settings
32
DSBL2/BYPASS
Function
L
CKOUT2 Enabled
M
CKOUT2 Disabled
H
PLL Bypass Mode w/ CKOUT2 Enabled
Rev. 1.0
Si5315
Crystal or
Reference Clock
Xtal/Clock
XA
XB
PLL Bypass
0
CKIN1+
CKIN1–
2
2
0
f3
CKIN2+
CKIN2–
2
DSPLL®
fOSC
CKOUT1+
CKOUT1–
1
SFOUT[1:0]
1
0
2
CKOUT2+
CKOUT2–
1
LOS1
LOS2
LOL
AUTOSEL
CS/CA
DBL2_BY
Signal Detect
Control
RST
BWSEL[1:0]
FRQSEL[3:0]
FRQTBL
Bandwidth
Control
VDD (1.8, 2.5, or 3.3 V)
Frequency
Control
GND
Figure 10. Bypass Signal
Rev. 1.0
33
Si5315
6. High-Speed I/O
6.1. Input Clock Buffers
The Si5315 provides differential inputs for the CKINn clock inputs. These inputs are internally biased to a common
mode voltage [see Table 2, “DC Characteristics”] and can be driven by either a single-ended or differential source.
Figure 11 through Figure 14 show typical interface circuits for LVPECL, CML, LVDS, or CMOS input clocks. Note
that the jitter generation improves for higher levels on CKINn (within the limits in Table 3, “AC Characteristics”).
AC coupling the input clocks is recommended because it removes any issue with common mode input voltages.
However, either ac or dc coupling is acceptable. Figures 11 and 12 show various examples of different input
termination arrangements. Unused inputs can be left unconnected.
3.3 V
Si5315
130 
130 
C
CKIN +
40 k 
LVPECL
Driver
300 
±
40 k
CKIN
82 
82 
VICM
_
C
Figure 11. Differential LVPECL Termination
3.3 V
Si5315
130 
C
CKIN +
Driver
40 k 
300 
±
40 k
CKIN _
82 
C
Figure 12. Single-ended LVPECL Termination
34
Rev. 1.0
VICM
Si5315
Si5315
C
CKIN +
CML/
LVDS
Driver
40 k
300 
100 
±
40 k
VICM
CKIN _
C
Figure 13. CML/LVDS Termination (1.8, 2.5, 3.3 V)
CMOS Driver
V DD
V DD
V DD
Si5315
R3
R1
V ICM
150 ohms
50
R2
C1
CKIN+
See Table
33 ohms
R4
150 ohms
VDD
R2
Notes
3.3 V
2.5 V
1.8 V
100 ohm
49.9 ohm
14.7 ohm
Locate R1 near CMOS driver
Locate other components near Si5317
Recalculate resistor values for other drive strengths
R5 40 kohm
100 nF
CKIN–
C2
100 nF
R6 40 kohm
Additional Notes:
1. Attenuation circuit limits overshoot and undershoot.
2. Not to be used with non-square wave input clocks.
Figure 14. CMOS Termination (1.8, 2.5, 3.3 V)
Rev. 1.0
35
Si5315
6.2. Output Clock Drivers
The Si5315 has a flexible output driver structure that can drive a variety of loads, including LVPECL, LVDS, CML,
and CMOS formats. The signal format is selected for both CKOUT1 and CKOUT2 outputs using the SFOUT [1:0]
pins. This modifies the output common mode and differential signal swing. See Table 2, “DC Characteristics” for
output driver specifications. The SFOUT [1:0] pins are three-level input pins, with the states designated as L
(ground), M (VDD/2), and H (VDD). Table 17 shows the signal formats based on the supply voltage and the type of
load being driven.
Table 17. Output Signal Format Selection (SFOUT)
Si5315
SFOUT[1:0]
Signal Format
HL
CML
HM
LVDS
LH
CMOS
LM
Disabled
MH
LVPECL
ML
Low-swing LVDS
All Others
Reserved
Z0 = 50 
100 
CKOUTn
Z0 = 50 
Rcvr
Figure 15. Typical Differential Output Circuit
Si5315
CMOS
Logic
CKOUTn
Optionally Tie CKOUTn
Outputs Together for Greater Strength
Figure 16. Typical CMOS Output Circuit (Tie CKOUTn+ and CKOUTn– Together)
For the CMOS setting (SFOUT = LH), both output pins drive single-ended in-phase signals. The CKOUT+/- can be
externally shorted together for greater drive strength specified in Table 2, “DC Characteristics”.
36
Rev. 1.0
Si5315
+
SFOUT[1:0] = LM (Output Disable)
100 
100 
CKOUTn
Output from
DSPLL
Figure 17. Disable CKOUTn Structure
The SFOUT [1:0] pins can also be used to disable both outputs. Disabling the output puts the CKOUTn+ and
CKOUTn– pins in a high-impedance state relative to VDD (common mode tri-state) while the two outputs remain
connected to each other through a 200  on-chip resistance (differential impedance of 200 ). The maximum
amount of internal circuitry is powered down, minimizing power consumption and noise generation. Recovery from
the disable mode requires additional time as specified in Table 3, “AC Characteristics”.
Rev. 1.0
37
Si5315
7. Crystal/Reference Clock Input
The device can use an external crystal or external clock as a reference. If an external clock is used, it must be ac
coupled. With appropriate buffers, the same external reference clock can be applied to CKINn. Although the
reference clock input can be driven single ended (See Figure 18), the best performance is with a crystal or low
jitter, differential clock source. No external loading capacitors are required for normal crystal operation.
3.3 V
150 
3.3 V
130 
Si5315
0.1 F
10 k
XA
CMOS buffer,
8 mA output current
150 
0.6 V
XB
0.1 F
For 2.5 V operation, change 130  to 82 .
Figure 18. CMOS External Reference Circuit
0 dBm into 50 
0.01 F
0.01 F
External Clock Source
50 
1.2 V
Si5315
XA
10 pF
10 k
XB
0.6 V
0.1 µF
Figure 19. Sinewave External Reference Clock Input Example
0.01 F
Si5315
1.2 V
XA
100 
LVPECL, CML, etc.
0.01 F
XB
10 k
10 k
0.6 V
Figure 20. Differential External Reference Clock Input Example
38
Rev. 1.0
Si5315
7.1. Crystal/Reference Clock Selection
The Si5315 requires either a low-jitter external oscillator or a low-cost fundamental mode crystal to be connected to
its XA/XB pins. This serves both as a jitter reference for jitter attenuation and as a reference oscillator for stability
during holdover. The frequency the reference is not directly related to either the input or the output clock
frequencies. The range of the reference frequency is from 37 to 41 MHz. For recommendations on the selection of
the reference frequency and a list of approved crystals, see the application note AN591 which can be downloaded
from www.silabs.com/timing/.
In holdover, the DSPLL remains locked to this external reference. Any changes in the frequency of this reference
when the DSPLL is in holdover will be tracked by the output of the device. Note that crystals can have temperature
sensitivities. Table 18 shows how the XTAL/CLOCK pin is used to select between a crystal and an external
oscillator.
Table 18. XA/XB Reference Sources
XTAL/CLOCK
Type
M
37–41 MHz external clock
L
40 MHz crystal
Because the crystal is used as a jitter reference, rapid changes of the crystal temperature can temporarily disturb
the output phase and frequency. For example, it is recommended that the crystal not be placed close to a fan that
is being turned off and on. If a situation such as this is unavoidable, the crystal should be thermally isolated with an
insulating cover.
7.1.1. Reference Drift
During holdover, long-term and temperature related drift of the reference input result in a one-to-one drift of the
output frequency. That is, the stability of the any-frequency output is identical to the drift of the reference frequency.
This means that for the most demanding applications where the drift of a crystal is not acceptable, an external
temperature compensated or ovenized oscillator will be required. Drift is not an issue unless the part is in holdover.
Also, the initial accuracy of the reference oscillator (or crystal) is not relevant.
Rev. 1.0
39
Si5315
7.1.2. Reference Jitter
Jitter on the reference input has a roughly one-to-one transfer function to the output jitter over the bandwidth
ranging from 100 Hz up to 30 kHz. If a crystal is used on the XA/XB pins, the reference will have low jitter if a
suitable crystal is in use. If the XA/XB pins are connected to an external reference oscillator, the jitter of the
external reference oscillator may contribute significantly to the output jitter.
A typical reference input-to-output jitter transfer function is shown in Figure 21.
Jitter Transfer XA/XB Reference to CKOUT
38.88 MHz XO, 38.88 MHz CKIN, 38.88 MHz CKOUT
5
0
Jitter Transfer (dB)
-5
-10
-15
-20
-25
-30
1
10
100
1000
10000
100000
Jitter Frequency (Hz)
Figure 21. Typical XA/XB Reference Jitter Transfer Function
40
Rev. 1.0
1000000
Si5315
8. Power Supply Filtering
This device incorporates an on-chip voltage regulator with excellent PSRR to power the device from a supply
voltage of 1.8, 2.5, or 3.3 V. The device requires minimal supply decoupling and no stringent layout or ground plane
islands. Internal core circuitry is driven from the output of this regulator while I/O circuitry uses the external supply
voltage directly. Table 3, “AC Characteristics” gives the sensitivity of the on-chip oscillator to changes in the supply
voltage. Refer to the Si5315 evaluation board for an example.
The center ground pad under the device must be electrically and thermally connected to the ground plane.
See Figure 26, “Ground Pad Recommended Layout,” on page 50.
System
Power
Supply
(1.8, 2.5, or
3.3 V)
0.1 uF
C1 – C3
Ferrite
Bead
1.0 uF
C4
VDD
GND &
GND Pad
Si5315
Figure 22. Typical Power Supply Bypass Network
Power Supply Noise to Output Transfer Function
-60
Power Supply Noise Rejection Ratio (dB)
-65
-70
-75
-80
-85
-90
-95
-100
-105
1
10
100
Frequency of Power Supply Noise (kHz)
1000
Figure 23. Fout = 155 MHz with 112 Hz Loop Bandwidth, 100 mVp-p Supply Noise
Rev. 1.0
41
Si5315
9. Typical Phase Noise Plots
The following is a typical phase noise plot. The clock input source was a Rohde and Schwarz model SML03 RF
Generator. The spectrum analyzer was either an Agilent model E5052B, model E4400A or model JS-500. The
Si5315 operates at 3.3 V with an ac coupled differential PECL output and an ac coupled differential sine wave input
from the RF generator at 0 dBm. Note that, as with any PLL, the output jitter that is below the loop BW is caused by
the jitter at the input clock, not the Si5315. Except as noted, loop BWs of 60 to 240 Hz were in use.
9.1. 10G LAN SyncE Example
Si5315 Typical Phase Noise 0
‐20
‐40
Fin=19.44 MHz;
Fout=125 MHz;
BW=111 Hz
‐60
Fin=19.44 MHz
Fout=156.25 MHz
BW=167 Hz
‐80
‐100
Fin=25 MHz
Fout=125 MHz
BW=111 Hz
‐120
Fin=25 MHz
Fout=156.25 MHz
BW=111 Hz
‐140
‐160
‐180
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
Frequency Plan
Fin=19.44 MHz Fin=19.44 MHz
Fin=25 MHz
Fin=25 MHz
Fout=156.25 MHz Fout=125 MHz Fout=156.25 MHz Fout=125 MHz
BW=167 Hz
BW=111 Hz
BW=111 Hz
BW=111 Hz
Jitter Integration Filter Band
RMS Jitter (fs)
IEEE802.3 (1.875 to 20 MHz)
232
240
251
240
SONET OC-192 (20 kHz to 80 MHz)
483
575
525
550
SONET OC-192 (4 to 80 MHz)
302
303
300
294
SONET OC-192 (50 kHz to 80 MHz)
467
564
510
537
SONET OC-48 (12 kHz to 20 MHz)
470
565
517
541
SONET OC-3 (12 kHz to 5 MHz)
422
524
471
503
BroadBand (800 Hz to 80 MHz)
511
584
533
557
42
Rev. 1.0
Si5315
CKOUT1–
CKOUT1+
SFOUT1
GND
SFOUT0
VDD
CKOUT2–
CKOUT2+
NC
10. Pin Descriptions: Si5315
36 35 34 33 32 31 30 29 28
RST 1
27 FRQSEL3
FRQTBL 2
26 FRQSEL2
LOS1 3
25 FRQSEL1
LOS2 4
XA 6
XB
24 FRQSEL0
GND
Pad
VDD 5
23 BWSEL1
22 BWSEL0
7
21 CS_CA
GND 8
20 GND
AUTOSEL 9
19 GND
LOL
CKIN1–
GND
CKIN1+
DBL2_BY
CKIN2–
CKIN2+
VDD
XTAL/CLOCK
10 11 12 13 14 15 16 17 18
Pin assignments are preliminary and subject to change.
Table 19. Si5315 Pin Descriptions
Pin #
1
Pin Name
RST
I/O
I
Signal Level
LVCMOS
2
FRQTBL
I
3-Level
3
LOS1
O
LVCMOS
4
LOS2
O
LVCMOS
Description
External Reset.
Active low input that performs external hardware reset of
device. Resets all internal logic to a known state. Clock outputs are tristated during reset. After rising edge of RST signal, the Si5315 will perform an internal self-calibration when
a valid input signal is present.
This pin has a weak pull-up.
Frequency Table Select.
Selects frequency table. (Table 9 on page 20.)
This pin has a weak pull-up and weak pull-down and defaults
to M.
Some designs may require an external resistor voltage
divider when driven by an active device that will tri-state.
CKIN1 Loss of Signal.
Active high loss-of-signal indicator for CKIN1. Once triggered, the alarm will remain active until CKIN1 is validated.
0 = CKIN1 present
1 = LOS on CKIN1
CKIN2 Loss of Signal.
Active high loss-of-signal indicator for CKIN2. Once triggered, the alarm will remain active until CKIN2 is validated.
0 = CKIN2 present
1 = LOS on CKIN2
Rev. 1.0
43
Si5315
Table 19. Si5315 Pin Descriptions (Continued)
Pin #
5, 10,
32
Pin Name
VDD
I/O
VDD
Signal Level
Supply
7
6
XB
XA
I
Analog
8,
15,19,
20,31
GND
GND
Supply
9
AUTOSEL
I
3-Level
11
XTAL/CLOCK
I
3-Level
12
13
CKIN2+
CKIN2–
I
44
Description
Supply.
The device operates from a 1.8, 2.5, or 3.3 V supply. Bypass
capacitors should be associated with the following VDD pins:
5
0.1 µF
10
0.1 µF
32
0.1 µF
A 1.0 µF should also be placed as close to device as is practical.
External Crystal or Reference Clock.
External crystal should be connected to these pins to use
internal oscillator based reference. Crystal or reference clock
selection is set by the XTAL/CLOCK pin.
Ground.
Must be connected to system ground. Minimize the ground
path impedance for optimal performance of this device.
Manual/Automatic Clock Selection.
Three level input that selects the method of input clock selection to be used.
L = Manual
M = Automatic non-revertive
H = Automatic revertive
This pin has a weak pull-up and weak pull-down and defaults
to M.
Some designs may require an external resistor voltage
divider when driven by an active device that will tri-state.
External Crystal or Reference Clock Rate.
Three level input that selects the type and rate of external
crystal or reference clock to be applied to the XA/XB port.
This pin has both a weak pull-up and a weak pull-down and
defaults to M.
L = Crystal
M = Clock (Default)
H = Reserved
Some designs may require an external resistor voltage
divider when driven by an active device that will tri-state.
Clock Input 2.
Differential input clock. This input can also be driven with a
single-ended signal. Input frequency selected from a table of
values. The same frequency must be applied to CKIN1 and
CKIN2.
Rev. 1.0
Si5315
Table 19. Si5315 Pin Descriptions (Continued)
Pin #
14
Pin Name
DBL2_BY
I/O
I
Signal Level
3-Level
16
17
CKIN1+
CKIN1–
I
Multi
18
LOL
O
LVCMOS
21
CS_CA
I/O
LVCMOS
23
22
BWSEL1
BWSEL0
I
3-Level
Description
Output 2 Disable/Bypass Mode Control.
Controls enable of CKOUT2 divider/output buffer path and
PLL bypass mode.
L = CKOUT2 enabled
M = CKOUT2 disabled
H = Bypass mode with CKOUT2 enabled. Bypass mode is
not supported with CMOS clock outputs (SFOUT = LH).
This pin has a weak pull-up and weak pull-down and defaults
to M.
Some designs may require an external resistor voltage
divider when driven by an active device that will tri-state.
Clock Input 1.
Differential input clock. This input can also be driven with a
single-ended signal. Input frequency selected from a table of
values. The same frequency must be applied to CKIN1 and
CKIN2.
PLL Loss of Lock Indicator.
This pin functions as the active high PLL loss of lock indicator.
0 = PLL locked
1 = PLL unlocked
Input Clock Select/Active Clock Indicator.
Input: If manual clock selection mode is chosen
(AUTOSEL = L), this pin functions as the manual
input clock selector. This input is internally deglitched
to prevent inadvertent clock switching during
changes in the CS input state.
0 = Select CKIN1
1 = Select CKIN2
If configured as input, must be set high or low.
Output: If automatic clock selection mode is chosen
(AUTOSEL = M or H), this pin indicates which of the
two input clocks is currently the active clock. If
alarms exist on both CKIN1 and CKIN2, indicating
that the holdover state has been entered, CA will
indicate the last active clock that was used before
entering the hold state.
0 = CKIN1 active input clock
1 = CKIN2 active input clock
Loop Bandwidth Select.
Three level inputs that select the DSPLL closed loop bandwidth. See Table 9 on page 20 for available settings.
These pins have both weak pull-ups and weak pull-downs
and default to M.
Some designs may require an external resistor voltage
divider when driven by an active device that will tri-state.
Rev. 1.0
45
Si5315
Table 19. Si5315 Pin Descriptions (Continued)
Pin #
27
26
25
24
Pin Name
FRQSEL3
FRQSEL2
FRQSEL1
FRQSEL0
I/O
I
Signal Level
3-Level
29
28
CKOUT1–
CKOUT1+
O
Multi
33
30
SFOUT0
SFOUT1
I
3-Level
Description
Frequency Select.
Three level inputs that select the input clock and clock multiplication ratio, depending on the FRQTBL setting.
These pins have both weak pull-ups and weak pull-downs
and default to M.
Some designs may require an external resistor voltage
divider when driven by an active device that will tri-state.
Clock Output 1.
Differential output clock with a frequency selected from a
table of values. Output signal format is selected by SFOUT
pins. Output is differential for LVPECL, LVDS, and CML compatible modes. For CMOS format, both output pins drive
identical single-ended clock outputs.
Signal Format Select.
Three level inputs that select the output signal format (common mode voltage and differential swing) for both CKOUT1
and CKOUT2.
SFOUT[1:0]
34
35
CKOUT2–
CKOUT2+
O
Multi
36
NC
—
—
GND
PAD
GND
GND
Supply
46
Signal Format
HH
Reserved
HM
LVDS
HL
CML
MH
LVPECL
MM
Reserved
ML
LVDS—Low Swing
LH
CMOS
LM
Disable
LL
Reserved
These pins have both weak pull-ups and weak pull-downs
and default to M.
Some designs may require an external resistor voltage
divider when driven by an active device that will tri-state.
Clock Output 2.
Differential output clock with a frequency selected from a
table of values. Output signal format is selected by SFOUT
pins. Output is differential for LVPECL, LVDS, and CML compatible modes. For CMOS format, both output pins drive
identical single-ended clock outputs.
No Connect.
Leave floating. Make no external connections to this pin for
normal operation.
Ground Pad.
The ground pad must provide a low thermal and electrical
impedance to a ground plane.
Rev. 1.0
Si5315
Table 20. Si5315 Pull-Up/Pull-Down
Pin #
Si5315
Pull
1
RST
U
2
FRQTBL
U, D
9
AUTOSEL
U, D
11
XTAL/
CLOCK
U, D
14
DBL2_BY
U, D
21
CS_CA
U, D
22
BWSEL0
U, D
23
BWSEL1
U, D
24
FRQSEL0
U, D
25
FRQSEL1
U, D
26
FRQSEL2
U, D
27
FRQSEL3
U, D
30
SFOUT1
U, D
33
SFOUT0
U, D
Rev. 1.0
47
Si5315
11. Ordering Guide
Ordering Part Number Output Clock Freq Range
Pkg
ROHS6, Pb-Free
Temp Range
Si5315A-C-GM
8 kHz–644.53 MHz
36-Lead 6x6 mm QFN
Yes
–40 to 85 °C
Si5315B-C-GM
8 kHz–125 MHz
36-Lead 6x6 mm QFN
Yes
–40 to 85 °C
Si5315-EVB
8 kHz–644.53 MHz
Evaluation Board
Note: Add an “R” at the end of the device to denote tape and reel options (i.e., Si5315A-C-GMR).
48
Rev. 1.0
Si5315
12. Package Outline: 36-Pin QFN
Figure 24 illustrates the package details for the Si5315. Table 21 lists the values for the dimensions shown in the
illustration.
Figure 24. 36-Pin Quad Flat No-Lead (QFN)
Table 21. Package Dimensions
Symbol
Millimeters
Symbol
Min
Nom
Max
A
0.80
0.85
0.90
A1
0.00
0.02
b
0.18
0.25
D
D2
e
Nom
Max
L
0.50
0.60
0.70
0.05

—
—
12º
0.30
aaa
—
—
0.10
bbb
—
—
0.10
4.10
ccc
—
—
0.08
ddd
—
—
0.10
eee
—
—
0.05
4.25
0.50 BSC
E
E2
Min
6.00 BSC
3.95
6.00 BSC
3.95
4.10
Millimeters
4.25
Notes:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to JEDEC outline MO-220, variation VJJD.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
Rev. 1.0
49
Si5315
13. PCB Land Pattern
Figure 25 illustrates the PCB land pattern for the Si5315. Figure 26 illustrates the recommended ground pad
layout. Table 22 lists the land pattern dimensions.
Figure 25. PCB Land Pattern
Figure 26. Ground Pad Recommended Layout
50
Rev. 1.0
Si5315
Table 22. PCB Land Pattern Dimensions
Dimension
Min
Max
e
0.50 BSC.
E
5.42 REF.
D
5.42 REF.
E2
4.00
4.20
D2
4.00
4.20
GE
4.53
—
GD
4.53
—
X
—
0.28
Y
0.89 REF.
ZE
—
6.31
ZD
—
6.31
Notes (General):
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification.
3. This Land Pattern Design is based on IPC-SM-782 guidelines.
4. All dimensions shown are at Maximum Material Condition (MMC). Least Material
Condition (LMC) is calculated based on a Fabrication Allowance of 0.05 mm.
Notes (Solder Mask Design):
1. All metal pads are to be non-solder mask defined (NSMD). Clearance between the
solder mask and the metal pad is to be 60 µm minimum, all the way around the pad.
Notes (Stencil Design):
1. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be
used to assure good solder paste release.
2. The stencil thickness should be 0.125 mm (5 mils).
3. The ratio of stencil aperture to land pad size should be 1:1 for the perimeter pads.
4. A 4 x 4 array of 0.80 mm square openings on 1.05 mm pitch should be used for the
center ground pad.
Notes (Card Assembly):
1. A No-Clean, Type-3 solder paste is recommended.
2. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for
Small Body Components.
Rev. 1.0
51
Si5315
14. Top Marking
14.1. Si5315 Top Marking (QFN)
14.2. Top Marking Explanation
Mark Method:
Laser
Font Size:
0.80 mm
Right-Justified
Line 1 Marking:
Si5315Q
Customer Part Number
Q = Speed Code: A, B
See Ordering Guide for options.
Line 2 Marking:
C-GM
C = Product Revision
G = Temperature Range –40 to 85 °C (RoHS6)
M = QFN Package
Line 3 Marking:
YYWWRF
YY = Year
WW = Work Week
R = Die Revision
F = Internal code
Assigned by the Assembly House. Corresponds to the year
and work week of the mold date.
Line 4 Marking:
Pin 1 Identifier
Circle = 0.75 mm Diameter
Lower-Left Justified
XXXX
Internal Code
52
Rev. 1.0
Si5315
DOCUMENT CHANGE LIST
Revision 0.1 to Revision 0.2

Expanded/added numerous operating sections to
initial data sheet
Revision 0.2 to Revision 0.25









Updated features and application list
Updated Section 1. "Electrical Specifications”
Added voltage regulator block to Figure 7
Revised footnotes in Table 9
Removed plan #203 from Table 9
Removed Figure 17. Crystal Oscillator with
Feedback Resistor diagram from Section 7.
"Crystal/Reference Clock Input”
Added XA/XB jitter transfer plot to Section 7.
"Crystal/Reference Clock Input”
Added PSRR transfer function plot to Section 8.
"Power Supply Filtering”
Updated Typical phase noise plot and RMS jitter
table in Section 9. "Typical Phase Noise Plots”
Revision 0.25 to Revision 0.26

Corrected Section 11. "Ordering Guide” Output
Clock Frequency Range for Si5315B-C-GM to
8 kHz–125 MHz.
Revision 0.26 to Revision 1.0








Updated Table 2 on page 4.
Updated Table 3 on page 8.
Updated Table 7 on page 13.
Moved “Typical Application Circuit” to page 14.
Added reference to AN591.
Bypass mode not supported with CMOS outputs.
Changed G.8262 compliance language.
Added frequency plans 103, 129, and 130.
Rev. 1.0
53
Si5315
CONTACT INFORMATION
Silicon Laboratories Inc.
400 West Cesar Chavez
Austin, TX 78701
Tel: 1+(512) 416-8500
Fax: 1+(512) 416-9669
Toll Free: 1+(877) 444-3032
Please visit the Silicon Labs Technical Support web page:
https://www.silabs.com/support/pages/contacttechnicalsupport.aspx
and register to submit a technical support request.
The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice.
Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences resulting from
the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features
or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Laboratories assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Silicon Laboratories products are not designed, intended, or authorized for use in applications intended to
support or sustain life, or for any other application in which the failure of the Silicon Laboratories product could create a situation where personal injury or death may occur. Should Buyer purchase or use Silicon Laboratories products for any such unintended or unauthorized application, Buyer shall indemnify and hold Silicon Laboratories harmless against all claims and damages.
Silicon Laboratories, Silicon Labs, and DSPLL are trademarks of Silicon Laboratories Inc.
Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders.
54
Rev. 1.0