ADN2913ACPZ [ADI]
Continuous Rate 6.5 Mbps to 8.5 Gbps Clock and Data Recovery IC with Integrated Limiting Amp/EQ;
| 型号： | ADN2913ACPZ |
| 厂家： | 
ADI |
| 描述： | Continuous Rate 6.5 Mbps to 8.5 Gbps Clock and Data Recovery IC with Integrated Limiting Amp/EQ |
| 文件： | 总37页 (文件大小：577K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Continuous Rate 6.5 Mbps to 8.5 Gbps Clock and
Data Recovery IC with Integrated Limiting Amp/EQ
Data Sheet
ADN2913
FEATURES
GENERAL DESCRIPTION
Serial data input: 6.5 Mbps to 8.5 Gbps
No reference clock required
The ADN2913 provides the receiver functions of quantization,
signal level detection, and clock and data recovery for continuous
data rates from 6.5 Mbps to 8.5 Gbps. The ADN2913 automatically
locks to all data rates without the need for an external reference
clock or programming. ADN2913 jitter performance exceeds all
jitter specifications required by SONET/SDH, including jitter
transfer, jitter generation, and jitter tolerance.
Exceeds SONET/SDH requirements for jitter transfer/
generation/tolerance
Quantizer sensitivity: 6.3 mV typical (limiting amplifier mode)
Optional limiting amplifier, equalizer (EQ), and 0 dB EQ inputs
Programmable jitter transfer bandwidth to support G.8251 OTN
Programmable slice level
The ADN2913 provides manual or automatic slice adjust and
manual sample phase adjusts. Additionally, the user can select a
limiting amplifier, equalizer, or 0 dB EQ at the input. The equalizer
is adaptive or it can be manually set.
Sample phase adjust (5.65 Gbps or greater)
Output polarity invert
Programmable LOS threshold via I2C
I2C interface to access optional features
Loss of signal (LOS) alarm (limiting amplifier mode only)
Loss of lock (LOL) indicator
PRBS generator/detector
Application aware power
352 mW at 8.5 Gbps, equalizer mode, no clock output
380 mW at 6.144 Gbps, limiting amplifier mode,
no clock output
340 mW at 622 Mbps, 0 dB EQ mode, no clock output
Power supplies: 1.2 V, flexible 1.8 V to 3.3 V, and 3.3 V
4 mm × 4 mm, 24-lead LFCSP
The receiver front-end loss of signal (LOS) detector
circuit indicates when the input signal level falls below a user-
programmable threshold. The LOS detection circuit has hysteresis
to prevent chatter at the LOS output. In addition, the input signal
strength can be read through the I2C registers.
The ADN2913 also supports pseudorandom binary sequence
(PRBS) generation, bit error detection, and input data rate
readback features.
The ADN2913 is available in a compact 4 mm × 4 mm, 24-lead
lead frame chip scale package (LFCSP). All ADN2913 specifica-
tions are defined over the ambient temperature range of −40°C
to +85°C, unless otherwise noted.
APPLICATIONS
SONET/SDH OC-1/OC-3/OC-12/OC-48 and all associated
FEC rates
1GE, 1GFC, 2GFC, 4GFC, 8GFC, CPRI OS/L.6 up to OS/L.60
Any rate regenerators/repeaters
FUNCTIONAL BLOCK DIAGRAM
REFCLKP/
REFCLKN
(OPTIONAL)
DATOUTP/
DATOUTN
CLKOUTP/
CLKOUTN
SCK
SDA
LOL
DATA RATE
2
2
I C REGISTERS
FREQUENCY
ACQUISITION
AND LOCK
I C_ADDR
CML
CML
DETECTOR
CLK
DDR
ADN2913
LOS
DETECT
LOS
FIFO
SAMPLE
PHASE
÷N
÷2
ADJUST
DOWNSAMPLER
AND LOOP
FILTER
DCO
LA
DATA
INPUT
SAMPLER
PIN
NIN
2
RXD
0dB EQ
EQ
RXCK
50Ω
50Ω
CLOCK
2
PHASE
I C
2
I C
SHIFTER
V
V
CC
CM
FLOAT
Figure 1.
Rev. A
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Technical Support
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ADN2913
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Limiting Amplifier ..................................................................... 22
Slice Adjust.................................................................................. 22
Edge Select................................................................................... 22
Loss of Signal (LOS) Detector .................................................. 23
Passive Equalizer ........................................................................ 24
0 dB EQ........................................................................................ 24
Lock Detector Operation .......................................................... 25
Harmonic Detector .................................................................... 25
Output Disable and Squelch ..................................................... 26
I2C Interface ................................................................................ 26
Reference Clock (Optional)...................................................... 26
Additional Features Available via the I2C Interface............... 28
Input Configurations ................................................................. 30
Applications Information.............................................................. 33
Transmission Lines..................................................................... 33
Soldering Guidelines for Lead Frame Chip Scale Package... 33
Outline Dimensions....................................................................... 34
Ordering Guide .......................................................................... 34
Applications....................................................................................... 1
General Description......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Jitter Specifications....................................................................... 5
Output and Timing Specifications............................................. 6
Timing Diagrams.......................................................................... 8
Absolute Maximum Ratings............................................................ 9
Thermal Characteristics .............................................................. 9
ESD Caution.................................................................................. 9
Pin Configuration and Function Descriptions........................... 10
Typical Performance Characteristics ........................................... 11
I2C Interface Timing and Internal Register Descriptions ......... 13
Register Map ............................................................................... 14
Theory of Operation ...................................................................... 20
Functional Description.................................................................. 22
Frequency Acquisition............................................................... 22
REVISION HISTORY
2/16—Rev. 0 to Rev. A
Changes to Figure 5........................................................................ 10
Changes to Table 7.......................................................................... 15
Updated Outline Dimensions....................................................... 33
Changes to Ordering Guide .......................................................... 33
12/13—Revision 0: Initial Version
Rev. A | Page 2 of 37
Data Sheet
ADN2913
SPECIFICATIONS
TA = TMIN to TMAX, VCC = VCCMIN to VCCMAX, VCC1 = VCC1MIN to VCC1MAX, VDD = VDDMIN to VDDMAX, VEE = 0 V, input data
pattern: PRBS 223 − 1, ac-coupled, I2C register default settings, unless otherwise noted.
Table 1.
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
DATA RATE SUPPORT RANGE
INPUT—DC CHARACTERISTICS
Peak-to-Peak Differential Input1
Input Resistance
0.0065
8.5
Gbps
PIN − NIN
Differential
1.0
105
V
Ω
95
100
0 dB EQ PATH—CML INPUT
Input Voltage Range
At PIN or NIN, dc-coupled, RX_TERM_FLOAT = 1
(float)
0.5
VCC
V
V
Input Common-Mode Level
DC-coupled (see Figure 33), 600 mV p-p differential, 0.65
RX_TERM_FLOAT = 1 (float)
VCC − 0.15
Differential Input Sensitivity
OC-48
8GFC2
22
200
mV p-p
mV p-p
Jitter tolerance scrambled pattern (JTSPAT),
ac-coupled, RX_TERM_FLOAT = 0 (VCM = 1.2 V),
BER = 1 × 10−12
LIMITING AMPLIFIER INPUT PATH
Differential Input Sensitivity
OC-48
BER = 1 × 10−10
6.3
8.3
mV p-p
mV p-p
8GFC2
JTSPAT, BER = 1 × 10−12
EQUALIZER INPUT PATH
Differential Input Sensitivity
15 inch FR-4, 100 Ω differential transmission line,
adaptive equalizer (EQ) on
JTSPAT, BER = 1 × 10−12
8GFC2
115
−12
mV p-p
dB
INPUT—AC CHARACTERISTICS
S11
At 7.5 GHz, differential return loss, see Figure 14
LOSS OF SIGNAL (LOS) DETECT
Loss of Signal Detect
10
5
128
5.7
135
110
mV p-p
mV p-p
mV p-p
dB
μs
μs
Loss of signal minimum program value
Loss of signal maximum program value
Hysteresis (Electrical)
LOS Assert Time
LOS Deassert Time
AC-coupled3
AC-coupled3
LOSS OF LOCK (LOL) DETECT
DCO Frequency Error for LOL Assert
With respect to nominal, data collected in lock to
reference (LTR) mode
1000
ppm
DCO Frequency Error for LOL Deassert
LOL Assert Response Time
With respect to nominal, data collected in LTR mode
10.0 Mbps
2.5 Gbps
250
10
51
ppm
ms
μs
8.5 Gbps, JTSPAT
25
μs
ACQUISITION TIME
Lock to Data (LTD) Mode
10.0 Mbps
2.5 Gbps
8.5 Gbps, JTSPAT
24
ms
ms
ms
ms
0.5
0.5
6.0
Optional LTR Mode4
DATA RATE READBACK ACCURACY
Coarse Readback
5
%
100
Fine Readback
In addition to reference clock accuracy
ppm
Rev. A | Page 3 of 37
ADN2913
Data Sheet
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
POWER SUPPLY VOLTAGE
VCC
VDD
VCC1
1.14
2.97
1.62
1.2
3.3
1.8
1.26
3.63
3.63
V
V
V
POWER SUPPLY CURRENT
VCC
Limiting amplifier mode, clock output enabled
1.25 Gbps
3.125 Gbps
4.25 Gbps
6.144 Gbps
8GFC,2 JTSPAT
1.25 Gbps
3.125 Gbps
4.25 Gbps
6.144 Gbps
8GFC,2 JTSPAT
1.25 Gbps
3.125 Gbps
277.1 311.0
256.2 288.3
270.1 304.0
303.1 340.4
319.1 359.5
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
mA
VDD
7.24
7.21
7.23
7.26
7.20
35.6
19.0
22.2
19.4
22.2
8.28
8.21
8.33
8.17
8.1
46.8
24.1
28.2
24.6
28.4
VCC1
4.25 Gbps
6.144 Gbps
8GFC,2 JTSPAT
TOTAL POWER DISSIPATION
Clock Output Enabled
Limiting amplifier mode, 1.25 Gbps
Limiting amplifier mode, 3.125 Gbps
Limiting amplifier mode, 4.25 Gbps
Limiting amplifier mode, 6.144 Gbps
Limiting amplifier mode, 8GFC,2 JTSPAT
Equalizer mode, 8.5 Gbps
420.4
365.5
388
422.5
446.6
352
mW
mW
mW
mW
mW
mW
mW
mW
°C
Clock Output Disabled
Limiting amplifier mode, 6.144 Gbps
0 dB EQ mode, 622 Mbps
380
340
OPERATING TEMPERATURE RANGE
−40
+85
1 See Figure 34.
2 Fibre Channel Physical Interface-4 standard, FC-PI-4, Rev 8.00, May 21, 2008.
3 When ac-coupled, the LOS assert and deassert times are dominated by the RC time constant of the ac coupling capacitor and the 100 Ω differential input termination
of the ADN2913 input stage.
4 This typical acquisition specification applies to all selectable reference clock frequencies in the range of 11.05 MHz to 176.8 MHz.
Rev. A | Page 4 of 37
Data Sheet
ADN2913
JITTER SPECIFICATIONS
TA = TMIN to TMAX, VCC = VCCMIN to VCCMAX, VCC1 = VCC1MIN to VCC1MAX, VDD = VDDMIN to VDDMAX, VEE = 0 V, input data
pattern: PRBS 223 − 1, ac-coupled to 100 Ω differential termination load, I2C register default settings, unless otherwise noted.
Table 2.
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
PHASE-LOCKED LOOP CHARACTERISTICS
Jitter Transfer Bandwidth (BW)1
8GFC2
OC-48
1242
663
157
175
44
1676
896
181
kHz
kHz
kHz
kHz
kHz
TRANBW[2:0] = 4 (default)
OTN mode, TRANBW[2:0] = 1
OC-12
OC-3
Jitter Peaking
8GFC2
OC-48
OC-12
OC-3
20 kHz to 80 MHz
20 kHz to 10 MHz
0.004
0.004
0.01
0.021
0.023
dB
dB
dB
dB
0.01
Jitter Generation
8GFC2
Unfiltered
Unfiltered
12 kHz to 20 MHz
Unfiltered
12 kHz to 20 MHz
Unfiltered
12 kHz to 5 MHz
Unfiltered
12 kHz to 5 MHz
Unfiltered
12 kHz to 1.3 MHz
Unfiltered
12 kHz to 1.3 MHz
Unfiltered
0.005
0.044
0.0025
UI rms
UI p-p
UI rms
OC-48
OC-12
OC-3
0.0046 UI rms
UI p-p
0.0276 UI p-p
UI rms
0.0011 UI rms
UI p-p
0.0076 UI p-p
UI rms
0.0156
0.0007
0.0038
0.0002
0.0008
0.0003 UI rms
UI p-p
0.0018 UI p-p
Jitter Tolerance
8GFC,2 JTSPAT
TRANBW[2:0] = 4 (default)
Sinusoidal Jitter at 340 kHz
Sinusoidal Jitter at 5.098 MHz
Sinusoidal Jitter at 80 MHz
Rx Jitter Tracking Test3
6.7
0.53
0.59
UI p-p
UI p-p
UI p-p
Voltage modulation amplitude (VMA) = 170 mV p-p at 100 MHz,
425 mV p-p at 100 MHz, 170 mV p-p at 2.5 GHz, and 425 mV p-p
at 2.5 GHz excitation frequency4
510 kHz, 1 UI
100 kHz, 5 UI
OC-48
10−12 <10−12
BER
BER
10−12 <10−12
1528
378
600 Hz
6 kHz
100 kHz
1 MHz
20 MHz
30 Hz
300 Hz
25 kHz
250 kHz
5 MHz
UI p-p
UI p-p
UI p-p
UI p-p
UI p-p
UI p-p
UI p-p
UI p-p
UI p-p
UI p-p
16.6
0.70
0.63
193
44
19.2
0.82
0.60
OC-12
Rev. A | Page 5 of 37
ADN2913
Data Sheet
Parameter
Test Conditions/Comments
Min
Typ
50.0
24.0
14.4
0.80
0.61
Max
Unit
OC-3
30 Hz
UI p-p
UI p-p
UI p-p
UI p-p
UI p-p
300 Hz
6500 Hz
65 kHz
1.3 MHz
1 Jitter transfer bandwidth is programmable by adjusting TRANBW[2:0] in the DPLLA register (Address 0x10).
2 Fibre Channel Physical Interface-4 standard, FC-PI-4, Rev 8.00, May 21, 2008.
3 Conditions of FC-PI-4, Rev 8.00, Table 27, 800-DF-EL-S apply.
4 Must have zero errors during the tests for an interval of time that is ≤10−12 BER to pass the tests.
OUTPUT AND TIMING SPECIFICATIONS
TA = TMIN to TMAX, VCC = VCCMIN to VCCMAX, VCC1 = VCC1MIN to VCC1MAX, VDD = VDDMIN to VDDMAX, VEE = 0 V, input data
pattern: PRBS 223 − 1, ac-coupled to 100 Ω differential termination load, I2C register default settings, unless otherwise noted.
Table 3.
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
CML OUTPUT CHARACTERISTICS
Data Differential Output Swing
8GFC,1 DATA_SWING[3:0] setting = 0xC (default)
8GFC,1 DATA_SWING[3:0] setting = 0xF (maximum)
8GFC,1 DATA_SWING[3:0] setting = 0x4 (minimum
8GFC,1 CLOCK_SWING[3:0] setting = 0xC (default)
8GFC,1 CLOCK_SWING[3:0] setting = 0xF
(maximum)
540
662
190
426
489
600
725
214
518
603
666
778
245
588
680
mV p-p
mV p-p
mV p-p
mV p-p
mV p-p
Clock Differential Output Swing
8GFC, CLOCK_SWING[3:0] setting = 0x4 (minimum) 166
213
VCC −
0.025
245
VCC
mV p-p
V
Output High Voltage
Output Low Voltage
VOH, dc-coupled
VCC − 0.05
VOL, dc-coupled
VCC − 0.36
VCC −
0.325
VCC −
0.29
V
CML OUTPUT TIMING CHARACTERISTICS
Rise Time
20% to 80%, at 8GFC,1 DATOUTN/DATOUTP
20% to 80%, at 8GFC,1 CLKOUTN/CLKOUTP
80% to 20%, at 8GFC,1 DATOUTN/DATOUTP
80% to 20%, at 8GFC,1 CLKOUTN/CLKOUTP
20.4
23.1
23
33.1
29.7
34.2
31.3
0.5
44
ps
ps
ps
ps
UI
UI
UI
UI
35.8
46.8
37.1
Fall Time
25
Setup Time, Full Rate Clock
Hold Time, Full Rate Clock
Setup Time, Half Rate/DDR Clock
Hold Time, Half Rate/DDR Clock
I2C INTERFACE DC CHARACTERISTICS
Input High Voltage
tS (see Figure 2)
tH (see Figure 2)
tS (see Figure 3)
tH (see Figure 3)
LVTTL
0.5
0.5
0.5
VIH
2.0
V
Input Low Voltage
VIL
0.8
V
Input Current
Output Low Voltage
I2C INTERFACE TIMING
VIN = 0.1 × VDD or VIN = 0.9 × VDD
VOL, IOL = 3.0 mA
See Figure 22
−10.0
+10.0
0.4
μA
V
SCK Clock Frequency
SCK Pulse Width High
SCK Pulse Width Low
Start Condition Hold Time
Start Condition Setup Time
Data Setup Time
Data Hold Time
SCK/SDA Rise/Fall Time
Stop Condition Setup Time
Bus Free Time Between Stop and
Start Conditions
400
kHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
tHIGH
tLOW
600
1300
600
600
100
300
20 + 0.1 Cb
600
1300
tHD;STA
tSU;STA
tSU;DAT
tHD;DAT
tR/tF
2
300
tSU;STO
tBUF
Rev. A | Page 6 of 37
Data Sheet
ADN2913
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
LVTTL DC INPUT CHARACTERISITICS
(I2C_ADDR Pin)
Input Voltage
High
Low
Input Current
High
Low
VIH
VIL
2.0
V
V
0.8
5
IIH, VIN = 2.4 V
IIL, VIN = 0.4 V
μA
μA
−5
LVTTL DC OUTPUT CHARACTERISITICS
(LOS/LOL Pins)
Output Voltage
High
Low
VOH, IOH = +2.0 mA
VOL, IOL = −2.0 mA
Optional LTR mode
VCM (no input offset, no input current),
see Figure 30, ac-coupled input
2.4
V
V
0.4
1.0
REFERENCE CLOCK CHARACTERISTICS
Input Compliance Voltage
(Common-Mode Voltage Referred
to Ground)
0.55
V
Minimum Input Drive
Reference Frequency
Required Accuracy3
100
100
mV p-p diff
MHz
ppm
See Figure 30, ac-coupled, differential input
AC-coupled, differential input
11.05
176.8
1 Fibre Channel Physical Interface-4 standard, FC-PI-4, Rev 8.00, May 21, 2008.
2 Cb is the total capacitance of one bus line in picofarads (pF). If mixed with high speed (HS) mode devices, faster rise/fall times are allowed (refer to the Philips
I2C Bus Specification, Version 2.1).
3 Required accuracy in dc-coupled mode is guaranteed by design as long as the clock common-mode voltage output matches the reference clock common-
mode voltage range.
Rev. A | Page 7 of 37
ADN2913
Data Sheet
TIMING DIAGRAMS
CLKOUTP
tH
tS
DATOUTP/
DATOUTN
Figure 2. Data to Clock Timing (Full Rate Clock Mode)
CLKOUTP
tS
tH
DATOUTP/
DATOUTN
Figure 3. Data to Clock Timing (Half Rate Clock/DDR Mode)
DATOUTP
DATOUTN
V
SE
1
V
2
V
SE
DIFF
0V
DATOUTP – DATOUTN
1
2
V
V
= SINGLE-ENDED VOLTAGE
DIFF
SE
= DIFFERENTIAL-ENDED VOLTAGE
Figure 4. Single-Ended vs. Differential Output Amplitude Relationship
Rev. A | Page 8 of 37
Data Sheet
ADN2913
ABSOLUTE MAXIMUM RATINGS
THERMAL CHARACTERISTICS
Table 4.
Thermal Resistance
Parameter
Rating
1.26 V
3.63 V
1.26 V
Supply Voltage (VCC = 1.2 V)
Supply Voltage (VDD and VCC1 = 3.3 V)
Maximum Input Voltage (REFCLKP/REFCLKN,
NIN/PIN)
Minimum Input Voltage (REFCLKP/REFCLKN,
NIN/PIN)
Maximum Input Voltage (SDA, SCK, I2C_ADDR)
Minimum Input Voltage (SDA, SCK, I2C_ADDR)
Maximum Junction Temperature
Thermal resistance is specified for the worst-case conditions,
that is, a device soldered in a circuit board for surface-mount
packages, for a 4-layer board with the exposed pad soldered to
VEE.
VEE − 0.4 V
Table 5. Thermal Resistance
1
2
3
3.63 V
VEE − 0.4 V
125°C
−65°C to +150°C
300°C
Package Type θJA
θJB
θJC
Unit
24-Lead LFCSP 45
5
11
°C/W
1 Junction to ambient.
2 Junction to board.
3 Junction to case.
Storage Temperature Range
Lead Temperature (Soldering, 10 sec)
ESD CAUTION
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
Rev. A | Page 9 of 37
ADN2913
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
PIN 1
INDICATOR
1
18 VCC
DD
VCC
PIN 2
17 V
16 NC
15 ATOUTP
ADN2913
3
NIN
TOP VIEW
D
VEE 4
(Not to Scale)
5
6
LOS
LOL
14
13
DATOUTN
VCC
NOTES
1. NC = NO CONNECT. TIE OFF TO GROUND.
2. THE EXPOSED PAD ON THE BOTTOM OF THE DEVICE
PACKAGE MUST BE CONNECTED TO VEE ELECTRICALLY.
THE EXPOSED PAD WORKS AS A HEAT SINK.
Figure 5. Pin Configuration
Table 6. Pin Function Descriptions
Pin No. Mnemonic Type1 Description
1
2
3
4
VCC
PIN
NIN
VEE
P
1.2 V Supply for Limiting Amplifier.
Positive Differential Data Input (CML).
Negative Differential Data Input (CML).
Ground for Limiting Amplifier.
AI
AI
P
5
6
7
8
LOS
LOL
VEE
VCC1
VDD
DO
DO
P
P
P
Loss of Signal Output (Active High).
Loss of Lock Output (Active High).
Digital Control Oscillator (DCO) Ground.
1.8 V to 3.3 V DCO Supply.
9
3.3 V High Supply.
10
11
12
13
14
15
16
17
18
19
20
21
22
CLKOUTN
CLKOUTP
VEE
DO
DO
P
Negative Differential Recovered Clock Output (CML).
Positive Differential Recovered Clock Output (CML).
Ground for CML Output Drivers.
1.2 V Supply for CML Output Drivers.
Negative Differential Retimed Data Output (CML).
Positive Differential Retimed Data Output (CML).
Do Not Connect. Leave this pin unconnected or tie it to VEE (ground).
3.3 V High Supply.
VCC
P
DATOUTN
DATOUTP
DNC
VDD
VCC
SCK
SDA
VCC
I2C_ADDR
DO
DO
DI
P
P
1.2 V Core Digital Supply.
DI
DIO
P
Clock for I2C Interface.
Bidirectional Data for I2C Interface.
1.2 V Core Digital Supply.
DI
I2C Address Setting. Sets the device I2C address = 0x80 when I2C_ADDR = 0. Sets the device I2C address = 0x82
when I2C_ADDR = 1.
23
24
REFCLKN
REFCLKP
EPAD
DI
DI
P
Negative Reference Clock Input (Optional).
Positive Reference Clock Input (Optional).
Exposed Pad (VEE). The exposed pad on the bottom of the device package must be connected to VEE
electrically. The exposed pad works as a heat sink.
1 P = power, AI = analog input, DI = digital input, DO = digital output, DIO = digital input/output.
Rev. A | Page 10 of 37
Data Sheet
ADN2913
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VCC = 1.2 V, VCC1 = 1.8 V, VDD = 3.3 V, VEE = 0 V, input data pattern: PRBS 215 − 1, ac-coupled inputs and outputs,
unless otherwise noted.
19.6ps/DIV
66.9ps/DIV
Figure 6. Output Eye Diagram at 8GFC
Figure 9. Output Eye Diagram at OC-48
5
0
1k
100
10
ADN2913
SONET MASK
ADN2913
SONET MASK
–5
–10
–15
–20
–25
–30
–35
–40
1
0.1
1k
10k
100k
1M
10M
100M
100
1k
10k
100k
1M
10M
100M
FREQUENCY (Hz)
JITTER FREQUENCY (Hz)
Figure 7. Jitter Tolerance: 8GFC
Figure 10. Jitter Transfer: 8GFC (TRANBW[2:0] = 4)
5
0
1k
100
10
ADN2913
ADN2913
SONET MASK
EQUIPMENT LIMIT
SONET MASK
–5
–10
–15
–20
–25
1
0.1
1k
10k
100k
1M
10M
100M
10
100
1k
10k
100k
1M
10M
100M
FREQUENCY (Hz)
JITTER FREQUENCY (Hz)
Figure 8. Jitter Tolerance: OC-48
Figure 11. Jitter Transfer: OC-48
Rev. A | Page 11 of 37
ADN2913
Data Sheet
4.70
4.65
4.60
4.55
4.50
4.45
4.40
4.35
4.30
4.25
4.20
4.15
1k
ADN2913
EQUIPMENT LIMIT
SONET MASK
100
10
1
0.1
10
155.52M
622.08M
2.4880G
2.6670G
100
1k
10k
100k
1M
10M
DATA RATE (bps)
JITTER FREQUENCY (Hz)
Figure 15. Sensitivities of SONET/SDH Data Rates (BER = 10−10
)
Figure 12. Jitter Tolerance: OC-12
0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
0
100
10
1
ADN2913
EQUIPMENT LIMIT
SONET MASK
0
2
4
6
8
10
12
14
16
0.1
10
EQ SETTING
100
1k
10k
100k
1M
10M
JITTER FREQUENCY (Hz)
Figure 16. BER in Equalizer Mode vs. EQ Compensation at 8GFC
(Measured with an 8GFC Signal of 400 mV p-p diff, on 15-Inch FR4 Traces,
with Variant EQ Compensation, Including Adaptive EQ)
Figure 13. Jitter Tolerance: OC-3
9
8
7
6
5
4
3
2
1
0
0
–5
–10
–15
–20
–25
–30
–35
–40
1M
10M
100M
1G
10G
100G
FREQUENCY (Hz)
DATARATE (bps)
Figure 17. Sensitivities of non-SONET/SDH Data Rates (BER = 10−12
)
Figure 14. Typical S11 Spectrum Performance
Rev. A | Page 12 of 37
Data Sheet
ADN2913
I2C INTERFACE TIMING AND INTERNAL REGISTER DESCRIPTIONS
R/W
CTRL.
SLAVE ADDRESS[6:0]
1
0
0
0
0
0
x
x
MSB = 1
SET BY 0 = W
PIN 22 1 = R
Figure 18. Slave Address Configuration
S
SLAVE ADDR, LSB = 0 (W) A(S) SUBADDR A(S) DATA A(S)
DATA A(S)
P
S = START BIT
P = STOP BIT
A(S) = ACKNOWLEDGE BY SLAVE
A(M) = ACKNOWLEDGE BY MASTER
Figure 19. I2C Write Data Transfer
S
SLAVE ADDR, LSB = 0 (W) A(S) SUBADDR A(S)
S
SLAVE ADDR, LSB = 1 (R) A(S) DATA A(M)
DATA A(M) P
S = START BIT
P = STOP BIT
A(M) = NO ACKNOWLEDGE BY MASTER
A(S) = ACKNOWLEDGE BY SLAVE
A(M) = ACKNOWLEDGE BY MASTER
Figure 20. I2C Read Data Transfer
START BIT
STOP BIT
SLAVE ADDRESS
SUBADDRESS
DATA
SDA
SCK
A6
A5
A7
A0
D7
D0
S
P
WR
ACK
ACK
ACK
SLAVE ADDR[4:0]
SUBADDR[6:1]
DATA[6:1]
Figure 21. I2C Data Transfer Timing
tF
tSU;DAT
tHD;STA
tBUF
tR
SDA
SCK
tSU;STO
tR
tF
tLOW
tHIGH
tHD;STA
tSU;STA
S
S
P
S
tHD;DAT
Figure 22. I2C Interface Timing Diagram
Rev. A | Page 13 of 37
ADN2913
Data Sheet
REGISTER MAP
Writing to register bits other than those labeled in Table 7 is not recommended and may cause unintended results.
Table 7. Internal Register Map1
Addr
(Hex)
Default
(Hex)
Reg Name
R/W
D7
D6
D5
D4
D3
D2
D1
D0
Readback/Status
FREQMEAS0
FREQMEAS1
FREQMEAS2
FREQ_RB1
FREQ_RB2
STATUSA
R
R
R
R
R
R
0x0
0x1
0x2
0x4
0x5
0x6
X
X
X
X
X
X
FREQ0[7:0] (RATE_FREQ[7:0])
FREQ1[7:0] (RATE_FREQ[15:8])
FREQ2[7:0] (RATE_FREQ[23:16])
VCOSEL[7:0]
X
X
FULLRATE
X
DIVRATE[3:0]
VCOSEL[9:8]
LOS
status
LOL
LOS done
Static LOL
X
RATE_
MEAS_
COMP
status
General Control
CTRLA
CTRLB
CTRLC
R/W
0x8
0x9
0xA
0x10
0x00
0x05
0
CDR_MODE[2:0]
0
Reset static RATE_
RATE_
MEAS_
RESET
LOL
MEAS_
EN
R/W
R/W
SOFTWARE_ INIT_
RESET
CDR
bypass
LOL_
CONFIG
LOS_PDN
0
LOS
polarity
0
0
0
FREQ_
ACQ
0
0
0
0
REFCLK_
PDN
1
FLL Control
LTR_MODE
D/PLL Control
DPLLA
R/W
0xF
0x00
0
LOL data
FREF_RANGE[1:0]
DATA_TO_REF_RATIO[3:0]
TRANBW[2:0]
R/W
R/W
0x10
0x13
0x1C
0x06
0
0
0
0
0
0
EDGE_SEL[1:0]
DPLLD
0
0
0
ADAPTIVE_
SLICE_EN
DLL_SLEW[1:0]
Phase
Slice
R/W
W
0x14
0x15
0x00
X
0
0
0
SAMPLE_PHASE[3:0]
Extended
slice
Slice[6:0]
LA_EQ
R/W
R
0x16
0x73
0x08
X
RX_TERM_
FLOAT
INPUT_SEL[1:0]
ADAPTIVE_
EQ_EN
EQ_BOOST[3:0]
Slice
SLICE_RB[7:0]
Readback
Output Control
OUTPUTA
R/W
R/W
0x1E
0x1F
0x00
0xCC
0
0
Data
squelch DISABLE
DATA_SWING[3:0]
DATOUT_
CLKOUT_
DISABLE
DDR_
DISABLE
DATA_
POLARITY
CLOCK_
POLARITY
OUTPUTB
CLOCK_SWING[3:0]
LOS Control
LOS_DATA
LOS_CTRL
R/W
R/W
0x36
0x74
0x00
0x00
LOS_DATA[7:0]
0
0
0
0
LOS_
WRITE
LOS_
LOS_
LOS_ADDRESS[2:0]
ENABLE
RESET
LOS_THRESH R/W
0x38
0x39
0x0A
0x00
LOS_THRESHOLD[7:0]
PRBS Control
PRBS Gen 1
R/W
DATA_
DATA_
0
DATA_
DATA_GEN_MODE[1:0]
CID_BIT CID_EN
GEN_EN
PRBS Gen 2
PRBS Gen 3
PRBS Gen 4
PRBS Gen 5
PRBS Gen 6
PRBS Rec 1
R/W
R/W
R/W
R/W
R/W
R/W
0x3A
0x3B
0x3C
0x3D
0x3E
0x3F
0x00
0x00
0x00
0x00
0x00
0x00
DATA_CID_LENGTH[7:0]
PROG_DATA[7:0]
PROG_DATA[15:8]
PROG_DATA[23:16]
PROG_DATA[31:24]
0
0
0
0
DATA_
RECEIVER_
CLEAR
DATA_
RECEIVER_
ENABLE
DATA_RECEIVER_
MODE[1:0]
PRBS Rec 2
PRBS Rec 3
R
R
0x40
0x41
0x00
0x00
PRBS_ERROR_COUNT[7:0]
X
X
X
X
X
X
X
PRBS_
ERROR
PRBS Rec 4
R
0x42
X
DATA_LOADED[7:0]
Rev. A | Page 14 of 37
Data Sheet
ADN2913
Addr
(Hex)
Default
(Hex)
Reg Name
PRBS Rec 5
PRBS Rec 6
PRBS Rec 7
ID/Revision
REV
R/W
R
D7
D6
D5
D4
D3
D2
D1
D0
0x43
0x44
0x45
X
X
X
DATA_LOADED[15:8]
DATA_LOADED[23:16]
DATA_LOADED[31:24]
R
R
R
R
R
R
0x48
0x49
0x20
0x21
0x54
0x15
0xA8
0x00
REV[7:0]
ID[7:0]
ID
HI_CODE
LO_CODE
Reserved
Reserved
1 X means don’t care.
Table 8. Status Register, STATUSA (Address 0x6)
Bits
Bit Name
Bit Description
D5
LOS status
0 = no loss of signal
1 = loss of signal
0 = locked
1 = frequency acquisition mode
0 = LOS action not completed
1 = LOS action completed
D4
D3
D2
D0
LOL status
LOS done
Static LOL
0 = no LOL event since last reset
1 = LOL event since last reset; clear using reset static LOL bit, Bit D2 in Register 0x8
Rate measurement complete
RATE_MEAS_COMP
0 = frequency measurement incomplete
1 = frequency measurement complete; clear using RATE_MEAS_RESET bit, Bit D0 in Register 0x8
Table 9. Control Register, CTRLA (Address 0x8)
Bits
D7
Bit Name
Bit Description
Reserved to 0.
D6:D4
CDR_MODE[2:0]
CDR modes.
001 = lock to data (LTD).
011 = lock to reference (LTR).
000, 010, 1xx = reserved.
D3
D2
D1
D0
Reserved to 0.
Reset static LOL
RATE_MEAS_EN
RATE_MEAS_RESET
Set to 1 to clear static LOL (Bit D2 in Register 0x6).
Fine data rate measurement enable. Set to 1 to initiate a rate measurement.
Rate measurement reset. Set to 1 to clear a rate measurement.
Rev. A | Page 15 of 37
ADN2913
Data Sheet
Table 10. Control Register, CTRLB (Address 0x9)
Bits
Bit Name
Bit Description
D7
SOFTWARE_RESET
INIT_FREQ_ACQ
Software reset. Write a 1 followed by a 0 to reset the device.
D6
Initiate frequency acquisition. Write a 1 followed by a 0 to initiate a frequency acquisition
(optional).
D5
CDR bypass
LOL_CONFIG
LOS_PDN
CDR bypass.
0 = CDR enabled.
1 = CDR bypassed.
LOL configuration.
0 = normal LOL.
D4
1 = static LOL.
D3
LOS power-down.
0 = normal LOS.
1 = LOS powered down.
LOS polarity.
D2
LOS polarity
0 = active high LOS pin.
1 = active low LOS pin.
Reserved to 0.
D1:D0
Table 11. Control Register, CTRLC (Address 0xA)
Bits
D7:D3
D2
Bit Name
Bit Description
Reserved to 0.
REFCLK_PDN
Reference clock power-down. Write a 0 to enable the reference clock.
D1
D0
Reserved to 0.
Reserved to 1.
Table 12. Lock to Reference Clock Mode Programming Register, LTR_MODE (Address 0xF)
Bits
Bit Name
Bit Description
D7
Reserved to 0
D6
LOL data
LOL data
0 = valid recovered clock vs. reference clock during tracking
1 = valid recovered clock vs. data during tracking
fREF range
00 = 11.05 MHz to 22.1 MHz
01 = 22.1 MHz to 44.2 MHz
10 = 44.2 MHz to 88.4 MHz
11 = 88.4 MHz to 176.8 MHz
D5:D4
D3:D0
FREF_RANGE[1:0]
DATA_TO_REF_RATIO[3:0] Data to reference ratio1 (N ≥ 2(N − 1), where N is the decimal equivalent of the binary code)
0000 = 1/2
0001 = 1
0010 = 2
0011 = 4
0100 = 8
…
1010 = 512
1 Data ÷ DIV_fREF, where DIV_fREF is the divided down reference referred to the 11.05 MHz to 22.1 MHz band (see the Reference Clock (Optional) section).
Data Rate/2(LTR_MODE[3:0] − 1) = REFCLK/2LTR_MODE[5:4]
Rev. A | Page 16 of 37
Data Sheet
ADN2913
Table 13. D/PLL Control Register, DPLLA (Address 0x10)
Bits
Bit Name
Bit Description
D7:D5
D4:D3
Reserved to 0.
EDGE_SEL[1:0]
Edge for phase detection. See the Edge Select section for more information.
00 = rising and falling edge data.
01 = rising edge data.
10 = falling edge data.
11 = rising and falling edge data.
D2:D0
TRANBW[2:0]
Transfer bandwidth. Scales the transfer bandwidth. Default value is 4, resulting in the 8GFC
default BW shown in Table 2. See the Transfer Bandwidth section for more information.
Transfer BW = Default BW × (TRANBW[2:0]/4)
Table 14. D/PLL Control Register, DPLLD (Address 0x13)
Bits
Bit Name
Bit Description
D7:D3
D2
D1:D0
Reserved to 0.
ADAPTIVE_SLICE_EN
DLL_SLEW[1:0]
Adaptive slice enable. 1 = enables automatic slice adjust.
DLL slew. Sets the BW of the DLL. See the DLL Slew section for more information.
Table 15. Phase Control Register, Phase (Address 0x14)
Bits
Bit Name
Bit Description
D7:D4
D3:D0
Reserved to 0.
SAMPLE_PHASE[3:0]
Adjust the phase of the sampling instant for data rates above 5.65 Gbps in steps of 1/32 UI. This
register is in twos complement format. See the Sample Phase Adjust section for more
information.
Table 16. Slice Level Control Register, Slice (Address 0x15)
Bits
Bit Name
Bit Description
D7
Extended slice
Extended slice enable.
0 = normal slice mode.
1 = extended slice mode.
D6:D0
Slice[6:0]
Slice is a digital word that sets the input threshold. See the Slice Adjust section for more information.
When slice[6:0] = 0000000, the slice function is disabled.
Table 17. Input Stage Programming Register, LA_EQ (Address 0x16)
Bits
Bit Name
Bit Description
D7
RX_TERM_FLOAT
Rx termination float.
0 = termination common-mode driven.
1 = termination common-mode floated (VCC = 1.2 V).
D6:D5
INPUT_SEL[1:0]
Input stage select.
00: limiting amplifier.
01: equalizer.
10: 0 dB EQ.
11: undefined.
D4
ADAPTIVE_EQ_EN
EQ_BOOST[3:0]
Enable adaptive EQ.
0 = manual EQ control.
1 = adaptive EQ enabled.
D3:D0
Equalizer gain. These bits set the EQ gain. See the Passive Equalizer section for more information.
Rev. A | Page 17 of 37
ADN2913
Data Sheet
Table 18. Output Control Register, OUTPUTA (Address 0x1E)
Bits
D7:D6
D5
Bit Name
Bit Description
Reserved to 0
Data squelch
Squelch
0 = normal data
1 = squelch data
D4
D3
D2
D1
D0
DATOUT_DISABLE
CLKOUT_DISABLE
DDR_DISABLE
Data output disable
0 = data output enabled
1 = data output disabled
Clock output disable
0 = clock output enabled
1 = clock output disabled
Double data rate
0 = DDR clock enabled
1 = DDR clock disabled
Data polarity
DATA_POLARITY
CLOCK_POLARITY
0 = normal data polarity
1 = flip data polarity
Clock polarity
0 = normal clock polarity
1 = flip clock polarity
Rev. A | Page 18 of 37
Data Sheet
ADN2913
Table 19. Output Swing Register, OUTPUTB (Address 0x1F)
Bits
Bit Name
Bit Description
D7:D4
DATA_SWING[3:0]
Adjust data output amplitude. Step size is approximately 50 mV differential.
Default register value is 0xC. Typical differential data output amplitudes are
0x1 = invalid.
0x2 = invalid.
0x3 = invalid.
0x4 = 200 mV.
0x5 = 250 mV.
0x6 = 300 mV.
0x7 = 345 mV.
0x8 = 390 mV.
0x9 = 440 mV.
0xA = 485 mV.
0xB = 530 mV.
0xC = 575 mV.
0xD = 610 mV.
0xE = 640 mV.
0xF = 655 mV.
D3:D0
CLOCK_SWING[3:0]
Adjust clock output amplitude. Step size is approximately 50 mV differential.
Default register value is 0xC. Typical differential clock output amplitudes are
0x1 = invalid.
0x2 = invalid.
0x3 = invalid.
0x4 = 200 mV.
0x5 = 250 mV.
0x6 = 300 mV.
0x7 = 345 mV.
0x8 = 390 mV.
0x9 = 440 mV.
0xA = 485 mV.
0xB = 530 mV.
0xC = 575 mV.
0xD = 610 mV.
0xE = 640 mV.
0xF = 655 mV.
Rev. A | Page 19 of 37
ADN2913
Data Sheet
THEORY OF OPERATION
The ADN2913 implements clock and data recovery for data
rates between 6.5 Mbps and 8.5 Gbps. A front end is configurable
to either amplify or equalize the nonreturn-to-zero (NRZ) input
waveform to full-scale digital logic levels, or to bypass a full
digital logic signal.
A separate PLL composed of a digital integrator and DCO
tracks the low frequency components of jitter. The initial
frequency of the DCO is set by a third loop that compares the
DCO frequency with the input data frequency. This third loop
also sets the decimation ratio of the digital downsampler.
The user can choose one of three input stages to process the
data: a high gain limiting amplifier with better than 10 mV
sensitivity, a high-pass passive equalizer with up to 10 dB of
boost at 5 GHz, or a 0 dB EQ buffer with 600 mV sensitivity.
The delay-locked and PLLs together track the phase of the input
data. For example, when the clock lags the input data, the phase
detector drives the DCO to a higher frequency and decreases the
delay of the clock through the phase shifter; both of these actions
serve to reduce the phase error between the clock and data.
Because the loop filter is an integrator, the static phase error is
driven to zero.
An on-chip LOS detector works with the high sensitivity limiting
amplifier. The default threshold for the LOS detector is the
sensitivity of the device, with a maximum threshold level of
128 mV p-p. The limiting amplifier slice threshold can use a
factory trim setting, a user defined threshold set by the I2C
interface, or an adjusted level for the best eye opening at the
phase detector.
Another view of the circuit is that the phase shifter implements
the zero required for frequency compensation of a second-order
PLL. This zero is placed in the feedback path and, therefore,
does not appear in the closed-loop transfer function. Because
this circuit has no zero in the closed-loop transfer, jitter peaking
is eliminated.
When the input signal is corrupted due to FR-4 or other
impairments in the printed circuit board (PCB) traces, a passive
equalizer can be one of the signal integrity options. The equalizer
high frequency boost is configurable through the I2C registers.
A user enabled adaptation is included that automatically adjusts
the equalizer to achieve the widest eye opening. The equalizer
can be manually set for any data rate, but adaptation is available
only at data rates greater than 5.5 Gbps.
The combination of the delay-locked and PLLs simultaneously
provide wideband jitter tolerance and narrow-band jitter
filtering. The simplified block diagram in Figure 23 shows that
Z(s)/X(s) is a second-order low-pass jitter transfer function that
provides excellent filtering. The low frequency pole is formed by
dividing the gain of the PLL by the gain of the DLL, where the
upsampling and zero-order hold in the DLL has a gain approaching
N at the transfer bandwidth of the loop. Note that the jitter transfer
has no zero, unlike an ordinary second-order PLL. This means that
the main PLL loop has no jitter peaking, making the circuit ideal
for signal regenerator applications, where jitter peaking in a cascade
of regenerators can contribute to hazardous jitter accumulation.
When a signal is presented to the clock and data recovery (CDR)
system, the ADN2913 acts as a delay-locked and phase-locked
loop (PLL) circuit for clock recovery and data retiming from an
NRZ encoded data stream. Input data is sampled by a high speed
clock. A digital downsampler accommodates data rates spanning
three orders of magnitude. Downsampled data is applied to a
binary phase detector (see Figure 23).
The error transfer, e(s)/X(s), has the same high-pass form as an
ordinary PLL up to the slew rate limit of the DLL with a binary
phase detector. This transfer function can be optimized to give
excellent wideband jitter tolerance because the jitter transfer
function, Z(s)/X(s), provides the narrow-band jitter filtering.
The phase of the input data signal is tracked by two separate
feedback loops. A high speed delay-locked loop (DLL) path
combines a digital integrator with a digitally controlled phase
shifter (PSH) on the DCO clock to track the high frequency
components of jitter.
PHASE-LOCKED LOOP (PLL)
BINARY
PHASE
DETECTOR
X(s)
Z(s)
K
× TRANBW
K
RECOVERED
CLOCK
PLL
DCO
s
INPUT
DATA
÷N
N
–1
I – z
DELAY-LOCKED LOOP (DLL)
–N
K
DLL
–1
I – z
PSH
N
–1
I – z
I – z
ZERO-ORDER HOLD
SAMPLE CLOCK
Z(s)
K
× TRANBW – K
PLL DCO
=
X(s) s × N × PSH × K
+ K
× TRANBW × K
DLL
PLL DCO
Figure 23. CDR Jitter Block Diagram
Rev. A | Page 20 of 37
Data Sheet
ADN2913
The delay-locked and PLLs contribute to overall jitter tolerance.
At low frequencies of input jitter on the data signal, the
The size of the DCO tuning range, therefore, has only a small
effect on the jitter tolerance. The DLL control range is now larger;
therefore, the phase shifter tracks the input jitter. An infinite
range phase shifter is used on the clock. Consequently, the
minimum range of timing mismatch between the clock at the data
sampler and the retiming clock at the output is limited by the
depth of the FIFO to 32 UI.
integrator in the loop filter provides high gain to track large
jitter amplitudes with small phase error. In this case, the
oscillator is frequency modulated and jitter is tracked as in an
ordinary PLL. The amount of low frequency jitter that can be
tracked is a function of the DCO tuning range. A wider tuning
range gives larger tolerance of low frequency jitter. The internal
loop control word remains small for small jitter frequency so
that the phase shifter remains close to the center of the range
and, thus, contributes little to the low frequency jitter tolerance.
There are two ways to acquire the data rate. The default mode is
for the frequency to lock to the input data, where a finite state
machine extracts frequency measurements from the data to
program the DCO and loop division ratio so that the sampling
frequency matches the data rate to within 250 ppm. The PLL is
enabled, driving this frequency difference to 0 ppm. The second
mode is to lock to the reference, in which case the user provides
a reference clock between 11.05 MHz and 176.8 MHz. Division
ratios must be written to a serial port register.
At medium jitter frequencies, the gain and tuning range of the
DCO are not large enough to track input jitter. In this case, the
DCO control word becomes large and saturates. As a result, the
DCO frequency remains at an extreme of the tuning range.
Rev. A | Page 21 of 37
ADN2913
Data Sheet
FUNCTIONAL DESCRIPTION
Accurate control of the slice threshold requires the user to read
back the factory trimmed offset, which is stored as a 7-bit
number in the slice readback register (Register 0x73). Use
Table 20 to decode the measured offset of the device, where an
LSB corresponds to 0.24 mV.
FREQUENCY ACQUISITION
The ADN2913 acquires the frequency from the input data over
a range of data frequencies from 6.5 Mbps to 8.5 Gbps. The lock
detector circuit compares the frequency of the DCO and the
frequency of the incoming data. When these frequencies differ by
more than 1000 ppm, the LOL pin is asserted and a new frequency
acquisition cycle is initiated. The DCO frequency is reset to the
lowest point of the range, and the internal division rate is set to
the lowest value of N = 1, which is the highest octave of data rates.
The frequency detector then compares this sampling rate frequency
to the data rate frequency and either increases N by a factor of 2
if the sampling rate frequency is greater than the data rate
frequency, or increases the DCO frequency if the data rate
frequency is greater than the sampling rate frequency. Initially,
the DCO frequency is incremented in large steps to aid fast
acquisition. As the DCO frequency approaches the data frequency,
the step size is reduced until the DCO frequency is within 250
ppm of the data frequency, at which point LOL is deasserted.
Table 20. Program Slice Level, Normal Slice Mode
(Extended Slice = 0)
Slice[6:0]
0000000
0000001
…
1000000
…
Decimal Value
Offset
0
1
…
64
…
127
Slice function disabled
−15 mV
…
0 mV
…
1111111
+14.75 mV
The amount of offset required for manual slice adjustment is
determined by subtracting the offset of the device from the
desired slice adjust level. Use Table 20 or Table 21 to determine
the code word to be written to the slice register.
When LOL is deasserted, the frequency-locked loop is turned
off. The PLL or DLL pulls in the DCO frequency until the DCO
frequency equals the data frequency.
An extended slice with coarser granularity for each LSB step is
found in Table 21. Setting the extended slice bit (Bit 7) = 1 in
Register 0x15 scales the full-scale range of the slice adjust by a
factor of 6.
LIMITING AMPLIFIER
The limiting amplifier has differential inputs (PIN and NIN)
that are each internally terminated with 50 Ω to an on-chip
voltage reference (VCM = 0.95 V typically). The inputs must be
ac-coupled. Input offset is factory trimmed to achieve better
than 10 mV p-p typical sensitivity with minimal drift. The
limiting amplifier can be driven differentially or single-ended.
DC coupling of the limiting amplifier is not possible because
the user must supply a common-mode voltage to exactly match
the internal common-mode voltage; otherwise, the internal
50 Ω termination resistors absorb the difference in common-
mode voltages.
Table 21. Program Slice Level, Extended Slice Mode
(Extended Slice = 1)
Slice[6:0]
0000000
0000001
…
Decimal Value
Offset
128
129
…
Slice function disabled
−100 mV
…
1000000
…
192
…
0 mV
…
1111111
255
+100 mV
Another reason that the limiting amplifier cannot be dc-coupled is
that the factory trimmed input offset becomes invalid. The offset is
adjusted to zero by differential currents from the slice adjust DAC
(see Figure 1). With ac coupling, all of the current goes to the 50 Ω
termination resistors on the ADN2913. However, with dc coupling,
this current is shared with the external drive circuit, and calibration
of the offset is lost. In addition, the slice adjust must have all the
current from the slice adjust DAC go to the resistors; otherwise,
the calibration is lost (see the Slice Adjust section).
When manual slice is desired, disable the dc offset loop, which
drives duty cycle distortion on the data to 0. Adaptive slice is
disabled by setting ADAPTIVE_SLICE_EN = 0 in Register 0x13.
EDGE SELECT
A binary, or Alexander phase, detector drives both the DLL and
PLL at all division rates. Duty cycle distortion on the received
data leads to a dead band in the phase detector transfer function
if phase errors are measured on both rising and falling data
transitions. This dead band leads to jitter generation of
unknown spectral composition whose peak-to-peak amplitude
is potentially large.
SLICE ADJUST
The quantizer slicing level can be offset by 100 mV in 1.6 mV
steps or by 15 mV in 0.24 mV steps to mitigate the effect of
amplified spontaneous emission (ASE) noise or duty cycle
distortion. The quantizer slice adjust level is set by the slice[6:0]
bits in Register 0x15.
The recommended usage of the device when the dc offset loop is
disabled is to compute phase errors exclusively on either the rising
data edges with EDGE_SEL[1:0] (Bits[D4:D3] in Register 0x10) = 1
(decimal) or falling data edges with EDGE_SEL[1:0] = 2. The
alignment of the clock to the rising data edges with EDGE_
SEL[1:0] = 1 is represented by the top two curves in Figure 24.
Rev. A | Page 22 of 37
Data Sheet
ADN2913
Duty cycle distortion with narrow 1s moves the significant
sampling instance where data is sampled to the right of center.
The alignment of the clock to the falling data edges with
EDGE_SEL[1:0] = 2 is represented by the first and third curves
in Figure 24. The significant sampling instance moves to the left
of center. Sample phase adjustment for rates above 5.65 Gbps
can move the significant sampling instance to the center of the
narrow 1 (or narrow 0) for best jitter tolerance.
Transfer Bandwidth
The transfer bandwidth can be adjusted using the I2C interface by
writing to TRANBW[2:0] in Register 0x10. The default value is 4.
When set to values below 4, the transfer bandwidth is reduced.
When set to values above 4, the transfer bandwidth is increased.
The resulting transfer bandwidth is based on the following formula:
TRANBW[2:0]
Transfer BW (Default Transfer BW)
4
DATA
For example, at OC-48, the default transfer bandwidth is
650 kHz. The resulting transfer bandwidth when
TRANBW[2:0] is changed is
EDGE_SEL[1:0] = 1
CLK1
EDGE_SEL[1:0] = 2
CLK2
TRANBW[2:0] = 1: transfer BW = 162.5 kHz
TRANBW[2:0] = 2: transfer BW = 325 kHz
TRANBW[2:0] = 3: transfer BW = 487.5 kHz
TRANBW[2:0] = 4: transfer BW = 650 kHz (default)
TRANBW[2:0] = 5: transfer BW = 812.5 kHz
TRANBW[2:0] = 6: transfer BW = 975 kHz
TRANBW[2:0] = 7: transfer BW = 1137.5 kHz
Figure 24. Phase Detector Timing
DLL Slew
Jitter tolerance beyond the transfer bandwidth of the CDR is
determined by the slew rate of the DLL implementing a delta
modulator on phase. Setting DLL_SLEW[1:0] = 2 (the default
value) in Register 0x13, configures the DLL to track 0.75 UI p-p
jitter at the highest frequency breakpoint in the SONET/SDH
jitter tolerance mask. This frequency scales with the rate as fp4 =
Rate (Hz)/2500 (for example, 1.0 MHz for OC-48). Peak-to-peak
tracking in UI at fp4 obeys the expression (1 + DLL_SLEW)/4 UI
p-p.
Reducing the transfer bandwidth is commonly used in OTN
applications. Never set TRANBW[2:0] = 0 because this value
makes the CDR open loop. Also, note that setting TRANBW[2:0]
to a value greater than 4 may cause a slight increase in jitter
generation and potential jitter peaking.
LOSS OF SIGNAL (LOS) DETECTOR
In some applications, full SONET/SDH jitter tolerance is not
needed. In this case, DLL_SLEW[1:0] can be set to 0, giving lower
jitter generation on the recovered clock and better high
frequency jitter tolerance.
The receiver front-end LOS detector circuit detects when the
input signal level falls below a user adjustable threshold.
There is typically 6 dB of electrical hysteresis on the LOS
detector to prevent chatter on the LOS pin. Therefore, if the
input level falls below the programmed LOS threshold, causing
the LOS pin to assert, the LOS pin is not deasserted until the
input level increases to 6 dB (2×) above the LOS threshold (see
Figure 25).
Sample Phase Adjustment
The phase of the sampling instant can be adjusted using the I2C
interface when the devices operate at data rates of 5.65 Gbps or
higher by writing to SAMPLE_PHASE[3:0] (Bits[D3:D0] in
Register 0x14). This feature allows the user to adjust the sampling
instant to improve the BER and jitter tolerance. Although the
default sampling instant chosen by the CDR is sufficient in most
applications, when dealing with degraded input signals, the BER
and jitter tolerance performance can be improved by manually
adjusting the phase.
LOS OUTPUT
INPUT LEVEL
HYSTERESIS
A total adjustment range of 0.5 UI is available, with 0.25 UI in each
direction, in increments of 1/32 UI. SAMPLE_PHASE[3:0] is a
twos complement number. The relationship between data and
the sampling clock is shown in Figure 26.
LOS THRESHOLD
t
Figure 25. LOS Detector Hysteresis
DATA
PHASE = 4
PHASE = 7
PHASE = –4
PHASE = –8
CLOCK
PHASE = 0
(DEFAULT)
NOTES
1. PHASE REFERS TO SAMPLE_PHASE[3:0]
Figure 26. Data vs. Sampling Clock
Rev. A | Page 23 of 37
ADN2913
Data Sheet
The LOS detector and the slice level adjust can be used simulta-
neously on the ADN2913. Therefore, any offset added to the
input signal by the slice[6:0] bits does not affect the LOS
detector measurement of the absolute input level.
Table 22 lists typical EQ settings for several trace lengths. The
values in Table 22 are based on measurements taken on a test
board with simple FR-4 traces. Table 23 lists the typical
maximum reach in inches of FR-4 of the EQ at several data
rates. If a real channel includes lossy connectors or vias, the
FR-4 reach length is lower. For any real-world system, it is
highly recommended to test several EQ settings with the real
channel to ensure the best signal integrity.
LOS Power-Down
By default, the LOS detector is enabled and consumes power.
The LOS detector is placed in a low power mode by setting
LOS_PDN = 1 (Bit D3 in Register 0x9).
Table 22. EQ Settings vs. Trace Length on FR-4
LOS Threshold
Trace Length (Inches)
Typical EQ Setting
The LOS threshold has a range between 0 mV and 128 mV and
is set by writing the number of millivolts (mV) to Register 0x36
followed by toggling the LOS_ENABLE bit in Register 0x74
while LOS_ADDRESS is set to 1. The following is a procedure
for writing the LOS threshold:
6
10
15
20 to 30
10
12
14
15
Table 23. Typical EQ Reach on FR-4 vs. Maximum Data
Rates Supported
Maximum Data Rate (Gbps) Typical EQ Reach on FR-4 (Inches)
1. Write 0x21 to LOS_CTRL (Register 0x74).
2. Write the desired threshold in millivolts to LOS_DATA
(Register 0x36).
3. Write 0x31 to LOS_CTRL (Register 0x74).
4. Write 0x21 to LOS_CTRL (Register 0x74).
4
8
10
11
30
20
15
10
The LOS threshold can be set to a value between 0 mV and
63 mV in 1 mV steps and from 64 mV to 128 mV in 2 mV
steps. In the lower range, all of the bits are active, giving 1
mV/LSB resolution, where Bit D0 is the LSB. In the upper
range, Bit D0 is disabled (that is, D0 = 0), making Bit D1 the
LSB and resulting in 2 mV/LSB resolution.
0 dB EQ
The 0 dB EQ path connects the input signal directly to the digital
logic inside the ADN2913. The 0 dB EQ is useful at lower data
rates where the signal is large (therefore, the limiting amplifier
is not needed and power can be saved by deselecting the limiting
amplifier) and unimpaired (therefore, the equalizer is not needed).
The signal swing of the internal digital circuit is 600 mV p-p
differential, the minimum signal amplitude that must be provided
as the input in 0 dB EQ mode.
The LOS_CTRL register contains the necessary address and
write enable bits to program this LOS threshold.
Signal Strength Measurement
The LOS detector measures and digitizes the peak-to-peak
amplitude of the received signal. A single shot measurement is
taken by writing the following sequence of bytes to LOS_CTRL
at Address 0x74: 0x7, 0x17, 0x7. When LOS_ENABLE goes low,
the peak-to-peak amplitude in millivolts is loaded into LOS_
DATA[7:0] (Register 0x36). The contents of LOS_DATA change
only when LOS_ENABLE (Bit D4 in Register 0x74) is toggled
low to high to low while LOS_ADDRESS[2:0] (Bits[D2:D0] in
Register 0x74) is set to 7.
In 0 dB EQ mode, the internal 50 Ω termination resistors can be
configured in one of two ways, either floated or tied to VCC = 1.2 V
(see Figure 31 and Table 27). By setting the RX_TERM_FLOAT
bit (Bit D7 in Register 0x16) to 1, these 50 Ω termination resistors
are floated internal to the ADN2913 (see Figure 35). By setting
the RX_TERM_FLOAT bit to 0, these 50 Ω termination resistors
are connected to VCC = 1.2 V (see Figure 36). In both termination
cases, the user must ensure a valid common-mode voltage on
the input.
PASSIVE EQUALIZER
A passive equalizer is available at the input to equalize large
signals that have undergone distortion due to PCB traces, vias,
or connectors. The adaptive EQ functions only at data rates
greater than 5.5 Gbps. Therefore, at rates less than 5.5 Gbps, the
EQ must be manually set.
When the termination is floated, the two 50 Ω resistors are a
purely differential termination. The input must conform to the
range of signals shown in Figure 33.
When the termination is connected to a 1.2 V VCC power supply
(see Figure 36 and Figure 37), the common-mode voltage is created
by the driver circuit and the 50 Ω resistors on the ADN2913.
For example, the driver can be an open-drain switched current (see
Figure 36), and the 50 Ω resistors return this current to VCC. In
Figure 36, the common-mode voltage is created by both the current
and the resistors.
The equalizer can be manually set using the LA_EQ register
(Register 0x16). An adaptive loop is also available to optimize
the EQ setting based on characteristics of the received eye at the
phase detector. If the channel is known in advance, set the EQ
manually to obtain the best performance; however, the adaptive
EQ finds the best setting in most cases.
Rev. A | Page 24 of 37
Data Sheet
ADN2913
In this case, ensure that the current is a minimum of 6 mA, which
gives a single-ended swing of 300 mV or a differential swing of
600 mV p-p differential, with VCM = 1.05 V (see Figure 33). The
maximum current is 10 mA, which gives a single-ended 500 mV
swing and differential 1.0 V p-p, with VCM = 0.95 V (see Figure 34).
For more information, see the Reference Clock (Optional) section.
In LTR mode, the lock detector monitors the difference in fre-
quency between the divided down DCO and the divided down
reference clock. The loss of lock signal, which appears on LOL
(Pin 6), is deasserted when the DCO is within 250 ppm of the
desired frequency. This enables the D/PLL, which pulls in the
DCO frequency by the remaining amount with respect to the
input data and acquires phase lock. If the frequency error exceeds
1000 ppm (0.1%), the loss of lock signal is reasserted and control
returns to the frequency loop, which reacquires lock with respect to
the reference clock. The LOL pin remains asserted until the DCO
frequency is within 250 ppm of the desired frequency. This
hysteresis is shown in Figure 27.
Another possibility is to back terminate the switched current
driver, as shown in Figure 37, with the two VCC supplies having
the same potential. In this example, the current is returned to
VCC by the two 50 Ω resistors in parallel, or 25 Ω, so that the
minimum current is 12 mA and the maximum current is 20 mA.
LOCK DETECTOR OPERATION
The lock detector on the ADN2913 has three modes of opera-
tion: normal mode, LOL detector operation using a reference
clock (LTR mode), and static LOL mode.
Static LOL Mode
The ADN2913 implements a static LOL feature that indicates
whether a loss of lock condition has occurred and remains asserted,
even if the ADN2913 regains lock, until the static LOL bit (Bit D2
in Register 0x6) is manually reset. If a loss of lock condition occurs,
this bit is internally asserted to logic high. The static LOL bit
remains high even after the ADN2913 reacquires lock to a new
data rate. This bit can be reset by writing 1, followed by 0, to the
reset static LOL bit (Bit D2 in Register 0x8). When reset, the static
LOL bit remains deasserted until another loss of lock condition
occurs.
Normal Mode
In normal mode, the ADN2913 is a continuous rate CDR that
locks onto any data rate from 6.5 Mbps to 8.5 Gbps without the
use of a reference clock as an acquisition aid. In this mode, the
lock detector monitors the frequency difference between the
DCO and the input data frequency, and deasserts the loss of
lock signal, which appears on LOL, Pin 6, when the DCO is
within 250 ppm of the data frequency. This enables the digital
PLL (D/PLL), which pulls the DCO frequency in the remaining
amount and acquires phase lock. If the input frequency error
exceeds 1000 ppm (0.1%), the loss of lock signal is reasserted
and control returns to the frequency loop, which begins a new
frequency acquisition. The LOL pin remains asserted until the
DCO locks onto a valid input data stream to within 250 ppm
frequency error. This hysteresis is shown in Figure 27.
Writing a 1 to LOL_CONFIG (Bit D4 in Register 0x9) causes
the LOL pin, Pin 6, to become a static LOL indicator. In this
mode, the LOL pin mirrors the contents of the static LOL bit
(Bit D2 in Register 0x6) and has the functionality described
previously. The LOL_CONFIG bit (Bit D4 in Register 0x9)
defaults to 0. In this mode, the LOL pin operates in the normal
operating mode; that is, it is asserted only when the ADN2913
is in acquisition mode and is deasserted when the ADN2913
has reacquired lock.
LOL
1
HARMONIC DETECTOR
The ADN2913 provides a harmonic detector that detects whether
the input data has changed to a lower harmonic of the data rate
than the one that the sampling clock is currently locked onto. For
example, if the input data instantaneously changes from OC-12,
622.08 Mbps, to an OC-3, 155.52 Mbps bit stream, this change
can be perceived as a valid OC-12 bit stream because the OC-3
data pattern is exactly 4× slower than the OC-12 pattern.
Therefore, if the change in data rate is instantaneous, a 101
pattern at OC-3 is perceived by the ADN2913 as a 111100001111
pattern at OC-12. If the change to a lower harmonic is
–1000
–250
0
250
1000 fDCO ERROR
(ppm)
Figure 27. Transfer Function of LOL
LOL Detector Operation Using a Reference Clock (LTR
Mode)
In lock to reference (LTR) mode, a reference clock is used as an
acquisition aid to lock the ADN2913 DCO. LTR mode is
enabled by setting CDR_MODE[2:0] to 3 (Bits[D6:D4] in
Register 0x8). The user must also write to FREF_RANGE[1:0]
and DATA_TO_REF_RATIO[3:0] (Bits[D5:D0] in Register 0xF)
to set the reference frequency range and the divide ratio of the
data rate with respect to the reference frequency. Finally, the
reference clock power-down to the reference clock buffer must
be deasserted by writing a 0 to REFCLK_PDN (Bit D2 in
Register 0xA). To maintain fastest acquisition, keep Bit D0 in
Register 0xA set to 1.
instantaneous, a typical inferior CDR may remain locked at the
higher data rate.
The ADN2913 implements a harmonic detector that automati-
cally identifies whether the input data has switched to a lower
harmonic of the data rate than the DCO is currently locked onto.
When a new harmonic is identified, the LOL pin is asserted,
and a new frequency acquisition is initiated. The ADN2913
automatically locks onto the new data rate, and the LOL pin is
deasserted.
Rev. A | Page 25 of 37
ADN2913
Data Sheet
The time to detect a lock to harmonic is
The R/W bit determines the direction of the data. Logic 0 on the
LSB of the first byte means that the master writes information to
the peripheral. Logic 1 on the LSB of the first byte means that
the master reads information from the peripheral.
216 × (Td/ρ)
where:
1/Td is the new data rate. For example, if the data rate is
switched from OC-12 to OC-3, then Td = 1/155.52 MHz.
ρ is the data transition density. Most coding schemes seek to
ensure that ρ = 0.5, for example, PRBS and 8B/10B.
The ADN2913 acts as a standard slave device on the bus. The
data on the SDA pin is eight bits long, supporting the 7-bit
addresses plus the R/W bit. The ADN2913 has subaddresses to
enable the user accessible internal registers (see Table 7).
When the ADN2913 is placed in lock to reference mode, the
harmonic detector is disabled.
The ADN2913, therefore, interprets the first byte as the device
address and the second byte as the starting subaddress. Auto-
increment mode is supported, allowing data to be read from or
written to the starting subaddress and each subsequent address
without manually addressing the subsequent subaddress. A data
transfer is always terminated by a stop condition. The user can
also access any unique subaddress register on a one-by-one
basis without updating all registers.
OUTPUT DISABLE AND SQUELCH
The ADN2913 has two types of output disable/squelch. The
DATOUTP/DATOUTN and CLKOUTP/CLKOUTN outputs
can be disabled by setting DATOUT_DISABLE and CLKOUT_
DISABLE (Bits[D4:D3] in Register 0x1E) high, respectively.
When an output is disabled, it is fully powered down, saving
approximately 30 mW per output. Disabling DATOUTP/
DATOUTN also disables the CLKOUTP/CLKOUTN outputs,
saving a total of about 60 mW of power.
Stop and start conditions can be detected at any stage of the
data transfer. If these conditions are asserted out of sequence
with normal read and write operations, they cause an immedi-
ate jump to the idle condition. During a given SCK high period,
issue one start condition, one stop condition, or a single stop
condition followed by a single start condition. If an invalid subad-
dress is issued by the user, the ADN2913 does not issue an
acknowledge and returns to the idle condition. If the user exceeds
the highest subaddress while reading back in auto-increment
mode, the highest subaddress register contents continue to be
output until the master device issues a no acknowledge. This
indicates the end of a read. In a no acknowledge condition, the
SDA line is not pulled low on the ninth pulse. See Figure 20 and
Figure 19 for sample read and write data transfers, respectively,
and Figure 21 for a more detailed timing diagram.
If it is desired to set the data output while leaving the clock
on, the output data can be squelched by setting the data squelch
bit (Bit D5 in Register 0x1E) high. In this mode, the data driver
remains powered, but the data itself is forced to a value of 0 (or
1, depending on the setting of DATA_POLARITY (Bit D1 in
Register 0x1E).
I2C INTERFACE
The ADN2913 supports a 2-wire, I2C-compatible serial bus
driving multiple peripherals. Two inputs, serial data (SDA) and
serial clock (SCK), carry information between any devices con-
nected to the bus. Each slave device is recognized by a unique
address. The slave address consists of the seven MSBs of an 8-bit
word. The upper six bits (Bits[6:1]) of the 7-bit slave address are
factory programmed to 100000. The LSB of the slave address (Bit 0)
is set by Pin 22, I2C_ADDR. The LSB of the word specifies either
a read or write operation (see Figure 18). Logic 1 corresponds to a
read operation, whereas Logic 0 corresponds to a write operation.
REFERENCE CLOCK (OPTIONAL)
A reference clock is not required to perform clock and data
recovery with the ADN2913. However, support for an optional
reference clock is provided. The reference clock can be driven
differentially or single-ended. If the reference clock is not used,
float both the REFCLKP and REFCLKN pins.
To control the device on the bus, the use the following protocol:
Two 50 Ω series resistors present a differential load between
REFCLKP and REFCLKN. Common mode is internally set to
0.56 × VCC by a resistor divider between VCC and VEE. See
Figure 28, Figure 29, and Figure 30 for sample configurations.
1. The master initiates a data transfer by establishing a start
condition, defined as a high to low transition on SDA while
SCK remains high. This indicates that an address/data
stream follows.
The reference clock input buffer accepts any differential signal
with a peak-to-peak differential amplitude of greater than
100 mV. The phase noise and duty cycle of the reference clock
are not critical, and 100 ppm accuracy is sufficient.
2. All peripherals respond to the start condition and shift the
next eight bits (the 7-bit address and the R/W bit). The bits
are transferred from MSB to LSB.
3. The peripheral that recognizes the transmitted address
responds by pulling the data line low during the ninth
clock pulse. This is known as an acknowledge bit.
4. All other devices withdraw from the bus at this point and
maintain an idle condition. In the idle condition, the
device monitors the SDA and SCK lines waiting for the
start condition and the correct transmitted address.
Rev. A | Page 26 of 37
Data Sheet
ADN2913
ADN2913
The reference clock can have a frequency from 11.05 MHz to
176.8 MHz. By default, the ADN2913 expects a reference clock
of between 11.05 MHz and 22.1 MHz. If the reference clock is
between 22.1 MHz and 44.2 MHz, 44.2 MHz and 88.4 MHz, or
between 88.4 MHz and 176.8 MHz, the user must configure the
ADN2913 to use the correct reference frequency range by setting
the two bits of FREF_RANGE[1:0] (Bits[5:4] in Register 0xF).
REFCLKP
REFCLKN
24
23
REFCLK
BUFFER
50Ω
50Ω
VCC/2
Table 24. LTR_MODE Register Settings
Figure 28. DC-Coupled, Differential REFCLKx Configuration
DATA_TO_REF_
FREF_RANGE[1:0] Bits Range (MHz) RATIO[3:0] Bits Ratio
VCC
ADN2913
REFCLKP
00
01
10
11
11.05 to 22.1 0000
22.1 to 44.2 0001
2−1
20
2n − 1
29
CLK
OSC
24
OUT
BUFFER
REFCLKN
23
44.2 to 88.4
88.4 to 176.8 1010
N
50Ω
50Ω
VCC/2
The user can specify a fixed integer multiple of the reference clock
to lock onto using DATA_TO_REF_RATIO[3:0] (Bits[D3:D0]
in Register 0xF), as follows:
Figure 29. AC-Coupled, Single-Ended REFCLKx Configuration
ADN2913
DATA_TO_REF_RATIO[3:0] = data rate ÷ DIV_fREF
REFCLKP
24
where DIV_fREF represents the divided down reference referred
to the 11.05 MHz to 22.1 MHz band.
REFCLK
BUFFER
REFCLKN
23
For example, if the reference clock frequency is 38.88 MHz and
the input data rate is 622.08 Mbps, then FREF_RANGE[1:0] is
set to 01 to give a divided down reference clock of 19.44 MHz.
DATA_TO_REF_RATIO[3:0] is set to 0110, that is, 6, because
50Ω
50Ω
VCC/2
Figure 30. AC-Coupled, Differential REFCLKx Configuration
622.08 Mbps/19.44 MHz = 2(6 − 1)
The reference clock can be used either as an acquisition aid for
the ADN2913 to lock onto data, or to measure the frequency
of the incoming data to within 0.01%. The modes are mutually
exclusive because, in the first use, the user can force the device
to lock onto only a known data rate; in the second use, the user
can measure an unknown data rate.
If the ADN2913 is operating in lock to reference mode and the
user changes the reference frequency, that is, the fREF range or the
f
REF ratio (Bits[D5:D4] or Bits[D3:D0], respectively, in Register
0xF), this change must be followed by writing a low to high to
low transition to the INIT_FREQ_ACQ bit (Bit D6 in Register 0x9)
to initiate a new lock to reference command.
Lock to reference mode is enabled by writing a 3 to CDR_
MODE[2:0] (Bits[D6:D4] in Register 0x8). An on-chip clock
buffer must be powered on by writing a 0 to REFCLK_PDWN
(Bit D2 in Register 0xA). Fine data rate readback mode is enabled
by writing a 1 to RATE_MEAS_EN (Bit D1 in Register 0x8).
Enabling lock to reference and data rate readback at the same
time causes an indeterminate state and is not supported.
By default in lock to reference clock mode, when lock has been
achieved and the ADN2913 is in tracking mode, the frequency
of the DCO is compared to the frequency of the reference clock.
If this frequency error exceeds 1000 ppm, lock is lost, LOL is
asserted, and the device relocks to the reference clock while
continuing to output a stable clock.
An alternative configuration is enabled by setting LOL data
(Bit D6 in Register 0xF) = 1. In this configuration, when the device
is in tracking mode, the frequency of the DCO is compared to
the frequency of the input data rather than the frequency of the
reference clock. If the frequency error exceeds 1000 ppm, lock is
lost, LOL is asserted, and the device relocks to the reference
clock while continuing to output a stable clock.
Using the Reference Clock to Lock Onto Data
In LTR mode, the ADN2913 locks onto a frequency derived
from the reference clock according to the following equation:
Data Rate/2(LTR_MODE[3:0] − 1) = REFCLK/2LTR_MODE[5:4]
The user must know exactly what the data rate is and provide a
reference clock that is a function of this rate. The ADN2913 can
still be used as a continuous rate device in this configuration if
the user can provide a reference clock that has a variable
frequency (see the AN-632 Application Note).
Rev. A | Page 27 of 37
ADN2913
Data Sheet
Using the Reference Clock to Measure Data Frequency
Consider the example of a 1.25 Gbps (GbE) input signal and a
reference clock source of 32 MHz at the PIN/NIN and REFCLKP/
REFCLKN ports, respectively. In this case, FREF_RANGE[1:0]
(Bits[D5:D4] in Register 0xF) = 01 and the reference frequency
falls into the range of 22.1 MHz to 44.2 MHz.
The user can also provide a reference clock to measure the
recovered data frequency. In this case, the ADN2913 compares
the frequency of the incoming data to the incoming reference
clock and returns a ratio of the two frequencies to 0.01%
(100 ppm). The accuracy error of the reference clock is added to
the accuracy error of the ADN2913 data rate measurement. For
example, if a 100 ppm accuracy reference clock is used, the total
accuracy of the measurement is 200 ppm.
After following Step 1 through Step 6, the readback value of
RATE_FREQ[23:0] is 0x13880, which is equal to 8 × 104. The
readback value of FULLRATE (Bit D6 in Register 0x5) is 1, and
the readback value of DIVRATE[3:0] (Bits[D5:D2] in Register
0x5) is 2. Inserting these values into Equation 1 yields
The reference clock can range from 11.05 MHz to 176.8 MHz.
Prior to reading back the data rate using the reference clock, the
FREF_RANGE[1:0] bits (Bits[D5:D4] in Register 0xF) must be
set to the appropriate frequency range with respect to the reference
clock being used, according to Table 24. A fine data rate readback is
then executed as follows:
((8 × 104) × (32 × 106))/(21 × 27 × 21 × 22) = 1.25 Gbps
If subsequent frequency measurements are required, keep
RATE_MEAS_EN (Bit D1 in Register 0x8) set to 1. It does not
need to be reset. The measurement process is reset by writing a
1 followed by a 0 to RATE_MEAS_RESET (Bit D0 in Register 0x8).
This initiates a new data rate measurement. Follow Step 2
through Step 6 to read back the new data rate. Note that a data
rate readback is valid only if the LOL pin is low. If LOL is high,
the data rate readback is invalid.
1. Apply the reference clock.
2. Write a 0 to REFCLK_PDN (Bit D2 in Register 0xA) to
enable the reference clock circuit.
3. Write to FREF_RANGE[1:0] (Bits[D5:D4] in Register 0xF)
to select the appropriate reference clock frequency circuit.
4. Write a 1 to RATE_MEAS_EN (Bit D1 in Register 0x8). This
enables the fine data rate measurement capability of the
ADN2913. This bit is level sensitive and does not need to be
reset to perform subsequent frequency measurements.
5. Write a low to high to low transition to RATE_MEAS_
RESET (Bit D0 in Register 0x8). This initiates a new data
rate measurement.
6. Read back RATE_MEAS_COMP (Bit D0 in Register 0x6). If
the bit is 0, the measurement is not complete. If it is 1, the
measurement is complete and the data rate can be read
back on RATE_FREQ[23:0], FULLRATE, and
Initiating a frequency measurement by writing a low to high to
low transition into RATE_MEAS_RESET (Bit D0 in Register 0x8)
also resets the RATE_MEAS_COMP bit (Bit D0 in Register 0x6).
The approximate time to complete a frequency measurement from
RATE_MEAS_RESET being written with a low to high to low
transition to when the RATE_MEAS_COMP bit returns high is
given by
211 2LTR[5:4]
(2)
Measuremen t Time
fREFCLK
LOS Configuration
The LOS detector output, LOS (Pin 5), can be configured to
be either active high or active low. If LOS polarity (Bit 2 in
Register 0x9) is set to Logic 0 (default), the LOS pin is active
high when a loss of signal condition is detected.
DIVRATE[3:0] (see Table 7). The approximate time for a
data rate measurement is given in Equation 2.
Use the following equation to determine the data rate:
ADDITIONAL FEATURES AVAILABLE VIA THE I2C
INTERFACE
(RATE _ FREQ[23:0] fREFLCLK
)
fDATARATE
(1)
2
LTR[5:4] 27 2FULLRATE 2DIVRATE[3:0]
where:
DATARATE is the data rate (Mbps).
RATE_FREQ[23:0] is from FREQ2[7:0] (most significant byte),
Coarse Data Rate Readback
f
The data rate can be read back over the I2C interface to approx-
imately 5% without using an external reference clock according to
the following formula:
FREQ1[7:0], and FREQ0[7:0] (least significant byte). See Table 7.
f
REFCLK is the reference clock frequency (MHz).
fDCO
FULLRATE = FREQ_RB2[6].
Data
(3)
2
FULLRATE 2DIVRATE[3:0]
DIVRATE[3:0] = FREQ_RB2[5:2].
where
MSB
LSB
FULLRATE = FREQ_RB2[6].
DIVRATE[3:0] = FREQ_RB2[5:2].
D23 to D16
D15 to D8
D7 to D0
FREQ0[7:0]
FREQ2[7:0]
FREQ1[7:0]
f
DCO is the frequency of the DCO, derived as shown in Table 25.
Rev. A | Page 28 of 37
Data Sheet
ADN2913
Four oscillator cores defined by VCOSEL[9:8] (Bits[D1:D0] in
Register 0x5) span the highest octave of data rates according to
Table 25.
The following steps configure the PRBS detector:
1. Set DATA_RECEIVER_ENABLE (Bit D2 in Register 0x3F)
to 1 and set DATA_RECEIVER_MODE[1:0] (Bits[D1:D0]
in Register 0x3F) according to the desired PRBS pattern
(0 = PRBS7; 1 = PRBS15; 2 = PRBS31). Setting DATA_
RECEIVER_MODE[1:0] to 3 leads to a one-shot sampling
of recovered data into DATA_LOADED[15:0].
Table 25. DCO Center Frequency vs. VCOSEL[9:8]
Core =
VCOSEL[9:8]
Min Frequency Max Frequency
(MHz) = Min_f(core) (MHz) = Max_f(core)
0
1
2
3
5570
7000
8610
10,265
7105
8685
10,330
11,625
2. Set DATA_RECEIVER_CLEAR (Bit D3 in Register 0x3F)
to 1 followed by 0 to clear PRBS_ERROR and
PRBS_ERROR_COUNT[7:0].
3. States of PRBS_ERROR (Bit D1 in Register 0x41) and
PRBS_ERROR_COUNT[7:0] (Bits[D7:D0] in Register 0x40)
can be frozen by setting DATA_RECEIVER_ENABLE (Bit D2
in Register 0x3F) to 0.
f
DCO is determined from VCOSEL[9:0] (Bits[D7:D0] in
Register 0x4, and Bits[D1:D0] in Register 0x5), according to the
following formula:
fDCO
Min_ f (core)
Worked Example
=
The following steps configure the PRBS generator:
Max _ f (core) Min_ f (core)
1. Set DATA_GEN_EN (Bit D2 in Register 0x39) = 1 to
enable the PRBS generator and set DATA_GEN_MODE[1:0]
(Bits[D1:D0] in Register 0x39) for the desired PRBS output
pattern (0 = PRBS7; 1 = PRBS15; 2 = PRBS31). An arbitrary
32-bit pattern stored as PROG_DATA[31:0] is activated by
setting DATA_GEN_MODE[1:0] to 3.
2. Strings of consecutive identical digits (CIDs) of sensed
DATA_CID_ BIT (Bit D5 in Register 0x39) can be
introduced in the generator by setting DATA_CID_EN
(Bit D4 in Register 0x39) set to 1. The length of CIDs is 8 ×
DATA_CID_LENGTH, which is set via Bits[D7:D0] in
Register 0x3A.
VCOSEL[7:0]
256
Read back the contents of the FREQ_RB1 and FREQ_RB2
registers. For example, with an OC-48 signal presented to the
PIN/NIN ports,
FREQ_RB1 = 0xCD
FREQ_RB2 = 0x46
FULLRATE (FREQ_RB2[6]) = 1
DIVRATE[3:0] (FREQ_RB2[5:2]) = 1
VCOSEL[9:8] core (FREQ_RB2[1:0]) = 2
Then
Table 26. PRBS Settings
fDCO
=
PRBS Pattern
DATA_GEN_MODE[1:0] PRBS Polynomial
PRBS7
PRBS15
PRBS31
PROG_DATA[31:0] 11
00
01
10
1 + X6 + X7
1 + X14 + X15
1 + X28 + X31
N/A
10,300 Mbps 8610 Mbps
8610 Mbps
205 9987.32 Mbps
256
and
9987.34Mbps
fdata
2496.84 Mbps
21 21
Double Data Rate Mode
The default output clock mode is a double data rate (DDR)
clock, where the output clock frequency is one-half the data
rate. DDR mode allows direct interfacing to FPGAs that support
clocking on both rising and falling edges. Setting DDR_DISABLE
(Bit D2 in Register 0x1E) = 1 enables full data rate mode. Full
data rate mode is not supported for data rates in the highest
octave between 5.6 Gbps and 8.5 Gbps.
Initiate Frequency Acquisition
A frequency acquisition can be initiated by writing a 1 followed
by a 0 to INIT_FREQ_ACQ (Bit D6 in Register 0x9). This initiates
a new frequency acquisition while keeping the ADN2913 in the
operating mode that was previously programmed in Register 0x8,
Register 0x9, and Register 0xA (CTRLA, CTRLB, and CTRLC
registers, respectively).
CDR Bypass Mode
PRBS Generator/Receiver
The CDR in the ADN2913 can be bypassed by setting the
CDR bypass bit (Bit D5 in Register 0x9) = 1. In this mode, the
ADN2913 feeds the input directly through the input amplifiers
to the output buffer, bypassing the CDR. The CDR bypass path is
intended for use in testing or debugging a system. Use the CDR
bypass path at data rates at or below 3.0 Gbps only.
The ADN2913 has an integrated PRBS generator and detector
for system testing purposes. The device is configurable as either
a PRBS detector or a PRBS generator.
Rev. A | Page 29 of 37
ADN2913
Data Sheet
Disable Output Buffers
The ADN2913 provides the option of disabling the output buffers
for power savings. The clock output buffer can be disabled by
setting Bit CLKOUT_DISABLE (Bit D3 in Register 0x1E) = 1.
This setting reduces the total output power by 30 mW. For a total
of 60 mW of power savings, such as in a low power standby mode,
both the CLKOUT and DATOUT buffers can be disabled together
by setting DATOUT_DISABLE (Bit D4 in Register 0x1E) = 1.
LOS
DETECT
LOS
LA
PIN
NIN
2
BYPASS
EQ
INPUT CONFIGURATIONS
2.9kΩ
2.9kΩ 50Ω
50Ω
The ADN2913 input stage can work with the signal source in an
ac-coupled or dc-coupled configuration. The ADN2913 supports
one of the following input modes: limiting amplifier, equalizer,
or 0 dB EQ. The ADN2913 can be configured to use any required
input configuration through the I2C bus. Figure 31 shows a block
diagram of the input stage circuit.
INPUT_SEL[1:0]
RX_TERM_FLOAT
V
CC
V
REF
FLOAT
Figure 31. Input Stage Block Diagram
The input signal path is configurable with the INPUT_SEL[1:0]
bits (Bits[D6:D5] in Register 0x16). Table 27 shows the
INPUT_SEL[1:0] bits and the input signal configuration.
Table 27. Input Signal Configuration
Selected Input
Limiting Amplifier
Equalizer
0 dB EQ (0 dB Buffer)
Not Defined
INPUT_SEL[1:0]
RX_TERM_FLOAT = 0
RX_TERM_FLOAT = 1
Not defined
Not defined
Float
00
01
10
11
VREF
VREF
VCC
Not defined
Not defined
Rev. A | Page 30 of 37
Data Sheet
ADN2913
Therefore,
τ = 12t
Choosing AC Coupling Capacitors
AC coupling capacitors at the inputs (PIN, NIN) and outputs
(DATOUTP, DATOUTN) of the ADN2913 must be chosen
such that the device works properly over the full range of data
rates used in the application. When choosing the capacitors, the
time constant formed with the two 50 ꢀ resistors in the signal
path must be considered. When a large number of consecutive
identical digits (CIDs) are applied, the capacitor voltage can
droop due to baseline wander (see Figure 32), causing pattern
dependent jitter (PDJ).
where:
τ is the RC time constant (C is the ac coupling capacitor, R = 100 ꢀ
seen by C).
t is the total discharge time.
t = nΤ
where:
n is the number of CIDs.
T is the bit period.
The user must determine how much droop is acceptable and
choose an ac coupling capacitor based on that amount of droop.
The amount of PDJ can then be approximated based on the
capacitor selection. The actual capacitor value selection may
require some trade-offs between droop and PDJ.
Calculate the capacitor value by combining the equations for τ
and t.
C = 12nT/R
When the capacitor value is selected, the PDJ can be
approximated as
For example, assuming that 2% droop is acceptable, the
maximum differential droop is 4%.
PDJps p-p = 0.5tR(1 − e(−nT/RC)/0.6
Normalizing to V p-p,
where:
Droop = Δ V = 0.04 V = 0.5 V p-p (1 − e−t/τ
)
PDJps p-p is the amount of pattern dependent jitter allowed,
<0.01 UI p-p typical.
tR is the rise time, which is equal to 0.22/BW; BW ≈ 0.7 (bit rate).
Note that this expression for tR is accurate only for the inputs.
The output rise time for the ADN2913 is ~30 ps regardless of
data rate.
VCC
ADN2913
V1
V2
PIN
DATOUTP
50Ω
2
C
CDR
TIA
OUT
C
V
REF
IN
50Ω
NIN
DATOUTN
V1b
V2b
1
2
3
4
V1
V1b
V2
VREF
VTH
V2b
VDIFF
VDIFF = V2 – V2b
VTH = ADN2913 QUANTIZER THRESHOLD
NOTES
1. DURING THE DATA PATTERNS WITH HIGH TRANSITION DENSITY, THE DIFFERENTIAL DC VOLTAGE AT V1 AND V2 IS ZERO.
2. WHEN THE TIA OUTPUTS CONSECUTIVE IDENTICAL DIGITS, V1 AND V1b ARE DRIVEN TO DIFFERENT DC LEVELS. V2 AND V2b DISCHARGE TO
THE V
LEVEL, WHICH EFFECTIVELY INTRODUCES A DIFFERENTIAL DC OFFSET ACROSS THE AC COUPLING CAPACITORS.
REF
3. WHEN THE BURST OF DATA STARTS AGAIN, THE DIFFERENTIAL DC OFFSET ACROSS THE AC COUPLING CAPACITORS IS APPLIED TO THE
INPUT LEVELS, CAUSING A DC SHIFT IN THE DIFFERENTIAL INPUT. THIS SHIFT IS LARGE ENOUGH SUCH THAT ONE OF THE STATES, EITHER
HIGH OR LOW, DEPENDING ON THE LEVELS OF V1 AND V1b WHEN THE TIA BEGAN DETECTING AND OUTPUTTING A CID DATA SYSTEM, IS CANCELLED OUT.
THE QUANTIZER DOES NOT RECOGNIZE THIS AS A VALID STATE.
4. THE DC OFFSET SLOWLY DISCHARGES UNTIL THE DIFFERENTIAL INPUT VOLTAGE EXCEEDS THE SENSITIVITY OF THE ADN2913. THE
QUANTIZER RECOGNIZES BOTH HIGH AND LOW STATES AT THIS POINT.
Figure 32. Example of Baseline Wander
Rev. A | Page 31 of 37
ADN2913
Data Sheet
DC-Coupled Application
Figure 36 shows the default dc-coupled configuration when
using the 0 dB EQ input. The two terminations are connected
directly to VCC in a normal CML fashion, giving a common
mode that is set by the dc signal strength from the driving chip.
The 0 dB EQ input has a high common-mode range and can
tolerate VCM up to and including VCC.
The inputs to the ADN2913 can also be dc-coupled. This can be
necessary in burst mode applications with long periods of CIDs
and where baseline wander cannot be tolerated. If the inputs to
the ADN2913 are dc-coupled, care must be taken not to violate
the input range and common-mode level requirements of the
ADN2913 (see Figure 33 and Figure 34). If dc coupling is required,
and the output levels of the transimpedance amplifier (TIA) do
not adhere to the levels shown in Figure 33 and Figure 34, level
shifting and/or attenuation must occur between the TIA outputs
and the ADN2913 inputs.
Figure 37 shows back terminated mode. The switched current
driver is back terminated, with the two VCC supplies having the
same potential.
See the 0 DB EQ section for more information.
ADN2913
1.2V
PIN
0.8V
50Ω
NIN
600mV p-p,
DIFF
V
= 1.05V
CM
INPUT (V)
= 0.65V
50Ω
50Ω
600mV p-p,
DIFF
V
CM
VCC
0.9V
I
0.5V
Figure 36. DC-Coupled Application, 0 dB EQ Input (Normal Mode)
VCC
Figure 33. Minimum Allowed DC-Coupled Input Levels
ADN2913
50Ω
50Ω
PIN
NIN
1.2V
50Ω
1.0V
1.0V p-p,
DIFF
V
= 0.95V
CM
50Ω
50Ω
INPUT (V)
= 0.75V
VCC
1.0V p-p,
DIFF
V
CM
0.7V
I
0.5V
Figure 37. DC-Coupled Application, 0 dB EQ Input (Back Terminated Mode)
Figure 34. Maximum Allowed DC-Coupled Input Levels
Figure 35 shows 0 dB EQ mode with 50 Ω termination resistors
floated internal to the ADN2913.
ADN2913
VCC
PIN
TIA
50Ω
NIN
50Ω
50Ω
Figure 35. DC-Coupled Application, 0 dB EQ Input
(Rx Termination Float Mode)
Rev. A | Page 32 of 37
Data Sheet
ADN2913
APPLICATIONS INFORMATION
TRANSMISSION LINES
SOLDERING GUIDELINES FOR LEAD FRAME CHIP
SCALE PACKAGE
Use of 50 ꢀ transmission lines is required for all high frequency
input and output signals to minimize reflections: PIN, NIN,
CLKOUTP, CLKOUTN, DATOUTP, and DATOUTN (also
REFCLKP and REFCLKN, if using a high frequency reference
clock, such as 155 MHz). The PIN and NIN input traces must be
matched in length, and the CLKOUTP, CLKOUTN, DATOUTP,
and DATOUTN output traces must match in length to avoid
skew between the differential traces.
The lands on the 24-lead LFCSP are rectangular. The PCB pad
for the lands is 0.1 mm longer than the package land length, and
0.05 mm wider than the package land width. Center the land on
the pad to ensure that the solder joint size is maximized. The
bottom of the lead frame chip scale package has a central exposed
pad. The pad on the PCB must be at least as large as this exposed
pad. The user must connect the exposed pad to VEE using plugged
vias to prevent solder from leaking through the vias during reflow.
This ensures a solid connection from the exposed pad to VEE.
The high speed inputs (PIN and NIN) are each internally termi-
nated with 50 ꢀ to an internal reference voltage (see Figure 31).
As with any high speed, mixed-signal circuit, take care to keep
all high speed digital traces away from sensitive analog nodes.
It is highly recommended to include as many vias as possible
when connecting the exposed pad to VEE. This minimizes the
thermal resistance between the die and VEE, and minimizes the
die temperature. It is recommended that the vias be connected
to a VEE plane, or planes, rather than a signal trace, to improve
heat dissipation, as shown in Figure 38.
The high speed outputs (DATOUTP, DATOUTN, CLKOUTP, and
CLKOUTN) are internally terminated with 50 ꢀ to VCC.
Placing an external VEE plane on the backside of the board
opposite the ADN2913 provides an additional benefit because
this allows easier heat dissipation into the ambient environment.
Figure 38. Connecting Vias to VEE
Rev. A | Page 33 of 37
ADN2913
Data Sheet
OUTLINE DIMENSIONS
4.10
4.00 SQ
3.90
PIN 1
INDICATOR
PIN 1
INDICATOR
24
1
19
18
0.50
BSC
2.40
2.30 SQ
2.20
EXPOSED
PAD
6
13
7
12
0.50
0.40
0.30
0.20 MIN
TOP VIEW
BOTTOM VIEW
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
0.80
0.75
0.70
0.05 MAX
0.02 NOM
SECTION OF THIS DATA SHEET.
COPLANARITY
0.08
0.203 REF
SEATING
PLANE
0.30
0.25
0.20
COMPLIANT TO JEDEC STANDARDS MO-220-WGGD-8.
Figure 39. 24-Lead Lead Frame Chip Scale Package [LFCSP]
4 mm × 4 mm Body and 0.75 mm Package Height
(CP-24-14)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
ADN2913ACPZ
ADN2913ACPZ-RL7
EVALZ-ADN2913
Temperature Range
−40°C to +85°C
−40°C to +85°C
Package Description
24-Lead LFCSP
24-Lead LFCSP, 7”Tape and Reel
Evaluation Board
Package Option
CP-24-14
CP-24-14
Ordering Quantity
490
1500
1 Z = RoHS Compliant Part.
Rev. A | Page 34 of 37
Data Sheet
NOTES
ADN2913
Rev. A | Page 35 of 37
ADN2913
NOTES
Data Sheet
Rev. A | Page 36 of 37
Data Sheet
NOTES
ADN2913
I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors).
©2013–2016 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D11777-0-2/16(A)
Rev. A | Page 37 of 37
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