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Continuous Rate 12.3Mb/s to 2.7Gb/s Clock and Data Recovery ICs
Preliminary Technical Data
FEATURES
Serial data input: 12.3 Mb/s to 2.7 Gb/s Exceeds ITU-T Jitter Specifications Integrated Limiting Amp: 6mV sensitivity (ADN2817 only) Adjustable slice level: 100 mV (ADN2817 only) Patented dual-loop clock recovery architecture Programmable LOS detect (ADN2817 only) Slice level and sample phase adjustments (ADN2817 only) Integrated PRBS Generator and Detector No reference clock required Loss of lock indicator Supports Double Data Rate Relative Bit Error Rate Monitor Rate Selectivity without the use of a reference clock I2CTM interface to access optional features Single-supply operation: 3.3 V Low power: 650/600 mW (ADN2817/ADN2818) 5 mm x 5 mm 32-lead LFCSP
ADN2817/ADN2818
PRODUCT DESCRIPTION
The ADN2817/ADN2818 provides the receiver functions of quantization, signal level detect, and clock and data recovery for continuous data rates from 12.3 Mb/s to 2.7 Gb/s. The ADN2817/ADN2818 automatically locks to all data rates without the need for an external reference clock or programming. All SONET jitter requirements are exceeded, including jitter transfer, jitter generation, and jitter tolerance. All specifications are quoted for -40C to +85C ambient temperature, unless otherwise noted. This device, together with a PIN diode and a TIA preamplifier, can implement a highly integrated, low cost, low power fiber optic receiver. The ADN2817/ADN2818 have many optional features available via an I2C interface, e.g. the user can read back the data rate that the ADN2817/ADN2818 is locked on to, or the user can set the device to only lock to one particular data rate if provisioning of data rates is required. The ADN2817/ADN2818 is available in a compact 5 mm x 5 mm 32-lead chip scale package.
APPLICATIONS
SONET OC-1/3/12/48 and all associated FEC rates Fibre Channel, 2x Fibre Channel , GbE, HDTV, etc. WDM transponders Regenerators/repeaters Test equipment
FUNCTIONAL BLOCK DIAGRAM
REFCLKP/N (optional)
LOL
CF1
CF2
VCC VEE
SLICEP/N
Slice Adjust (ADN2817 only)
Freq/ Lock Det
Loop Filter
PIN NIN VREF Phase Shifter Phase Det. Loop Filter
VCO
LOS Detect (ADN2817 only)
Data Re-Timing
I2C Registers CLKOUTP/N
THRADJ
SDOUT DATAOUTP/N
SCK SDA
Figure 1 ADN2817/ADN2818 Functional Block Diagram Rev.PrA
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
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ADN2817/ADN2818
Preliminary Technical Data
TABLE OF CONTENTS
Specifications..................................................................................... 3 Jitter Specifications....................................................................... 4 Output and Timing Specifications ............................................. 5 Absolute Maximum Ratings............................................................ 6 Thermal Characteristics .............................................................. 7 ESD Caution.................................................................................. 7 Timing Characteristics..................................................................... 8 Pin Configuration and Function Descriptions............................. 9 Typical Performance Characteristics ........................................... 10 I2C Interface Timing and Internal Register Description........... 11 Terminology .................................................................................... 15 Jitter Specifications ......................................................................... 16 Jitter Generation ......................................................................... 16 Jitter Transfer............................................................................... 16 Jitter Tolerance ............................................................................ 16 Theory of Operation ...................................................................... 17 Functional Description.................................................................. 19 Frequency Acquisition............................................................... 19 Limiting Amplifier ..................................................................... 20 Slice Adjust.................................................................................. 20 Loss of Signal (LOS) Detector .................................................. 20 Lock Detector Operation .......................................................... 19 Harmonic Detector .................................................................... 20 Squelch Mode ............................................................................. 21 I2C Interface ............................................................................... 21 Reference Clock (Optional) ...................................................... 21 Applications Information .............................................................. 27 PCB Design Guidelines ............................................................. 27 DC-Coupled Application .......................................................... 29 Coarse Data Rate Readback Look-Up Table............................... 31 Outline Dimensions ....................................................................... 33 Ordering Guide .......................................................................... 33
REVISION HISTORY
Revision 0: Initial Version Revision A: Remove Minimum Supply Current Spec Revision B: Update spec table
Rev. PrA | Page 2 of 35
Preliminary Technical Data SPECIFICATIONS
ADN2817/ADN2818
TA = TMIN to TMAX, VCC = VMIN to VMAX, VEE = 0 V, CF = 0.47 F, SLICEP = SLICEN = VEE, Input Data Pattern: PRBS 223 - 1, unless otherwise noted. Table 1.
Parameter QUANTIZER--DC CHARACTERISTICS Input Voltage Range Peak-to-Peak Differential Input Input Common Mode Level Differential Input Sensitivity Input Overdrive Input Offset Input RMS Noise QUANTIZER--AC CHARACTERISTICS Data Rate S11 Input Resistance Input Capacitance QUANTIZER--SLICE ADJUSTMENT Gain Differential Control Voltage Input Control Voltage Range Slice Threshold Offset LOSS OF SIGNAL DETECT (LOS) Loss of Signal Detect Range (see Figure 5) Hysteresis (Electrical) Conditions @ PIN or NIN, dc-coupled PIN - NIN DC-coupled (see Figure 28, Figure 29, and Figure 30) 223 - 1 PRBS, ac-coupled,1 BER = 1 x 10-10 (see Figure 12) BER = 1 x 10-10 12.3 @ 2.5 GHz Differential -15 100 0.65 TBD VEE 1 RThresh = 0 RThresh = 100 k OC-48 RThresh = 0 RThresh = 100 k OC-1 RThresh = 0 RThresh = 10 k DC-coupled2 DC-coupled2 With respect to nominal With respect to nominal 12.3 Mb/s OC-12 OC-48 OC-48 OC-12 OC-3 OC-1 12.3 Mb/s TBD TBD TBD TBD TBD TBD TBD TBD 1000 250 4 1.0 1.0 1.3 2.0 3.4 9.8 40.0 10.0 TBD TBD TBD TBD TBD TBD 0.1 TBD TBD 0.95 Min 1.8 2.3 TBD TBD 2.5 TBD TBD TBD TBD 2700 Typ Max 2.8 2.0 2.8 Unit V V V mV p-p mV p-p V V rms Mb/s dB pF V/V V V mV mV mV dB dB dB dB ns ns ppm ppm ms s s ms ms ms ms ms ms
SLICEP - SLICEN = 0.5 V SLICEP - SLICEN DC level @ SLICEP or SLICEN
LOS Assert Time LOS De-Assert Time LOSS OF LOCK DETECT (LOL) VCO Frequency Error for LOL Assert VCO Frequency Error for LOL De-Assert LOL Response Time
ACQUISITION TIME Lock to Data Mode
Optional Lock to REFCLK Mode
1 2
PIN and NIN should be differentially driven and ac-coupled for optimum sensitivity. When ac-coupled, the LOS assert and de-assert time is dominated by the RC time constant of the ac coupling capacitor and the 50 input termination of the ADN2817/ADN2818 input stage.
Rev.Pr A | Page 3 of 35
ADN2817/ADN2818
Parameter DATA RATE READBACK ACCURACY Coarse Readback Fine Readback Conditions (See Table 14) In addition to REFCLK accuracy Data rate < 20 Mb/s Data rate > 20 Mb/s 3.0 -40
Preliminary Technical Data
Min Typ 10 200 100 3.6 TBD +85 Max Unit % ppm ppm V mA C
POWER SUPPLY VOLTAGE POWER SUPPLY CURRENT OPERATING TEMPERATURE RANGE
3.3 200
JITTER SPECIFICATIONS
TA = TMIN to TMAX, VCC = VMIN to VMAX, VEE = 0 V, CF = 0.47 uF, SLICEP = SLICEN = VEE, Input Data Pattern: PRBS 223 - 1, unless otherwise noted. Table 2.
Parameter PHASE-LOCKED LOOP CHARACTERISTICS Jitter Transfer BW Conditions OC-48 OC-12 OC-3 OC-48 OC-12 OC-3 OC-48, 12 kHz to 20 MHz OC-12, 12 kHz to 5 MHz OC-3, 12 kHz to 1.3 MHz Jitter Tolerance OC-48, 223 - 1 PRBS 600 Hz 6 kHz 100 kHz 1 MHz 20 MHz OC-12, 223 - 1 PRBS 30 Hz1 300 Hz1 25 kHz 250 kHz1 OC-3, 223 - 1 PRBS 30 Hz1 300 Hz1 6500 Hz 65 kHz See Figure XX. Min Typ Max TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD Unit kHz kHz kHz dB dB dB UI rms UI p-p UI rms UI p-p UI rms 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 UI p-p UI p-p UI p-p UI p-p dB
Jitter Peaking
Jitter Generation
0 0 0 0.001 0.02 0.001 0.01 0.001 0.01 TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD
Power Supply Rejection
1
Jitter tolerance of the ADN2817/ADN2818 at these jitter frequencies is better than what the test equipment is able to measure.
Rev. PrA | Page 4 of 35
Preliminary Technical Data
OUTPUT AND TIMING SPECIFICATIONS
Table 3.
Parameter CML OUPUT CHARACTERISTICS (CLKOUTP/N, DATAOUTP/N) Single-Ended Output Swing Differential Output Swing Output High Voltage Output Low Voltage CML Ouputs Timing Rise Time Fall Time Setup Time Hold Time I2C INTERFACE DC CHARACTERISTICS Input High Voltage Input Low Voltage Input Current Output Low Voltage I2C INTERFACE TIMING 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 a Stop and a Start REFCLK CHARACTERISTICS Input Voltage Range Conditions Min Typ
ADN2817/ADN2818
Max
Unit
VSE (see Figure 3) VDIFF (see Figure 3) VOH VOL 20% to 80% 80% to 20% TS (see Figure 2), OC-48 TH (see Figure 2), OC-48 LVCMOS VIH VIL VIN = 0.1 VCC or VIN = 0.9 VCC VOL, IOL = 3.0 mA (See Figure 11) tHIGH tLOW tHD;STA tSU;STA tSU;DAT tHD;DAT TR/TF tSU;STO tBUF Optional lock to REFCLK mode @ REFCLKP or REFCLKN VIL VIH
300 600 VCC - 0.6
350 700 VCC - 0.35
600 1200 VCC VCC - 0.3 TBD TBD 250 250
mV mV V V ps ps ps ps V V A V kHz ns ns ns ns ns ns ns ns ns
150 150 0.7 VCC -10.0
200 200
0.3 VCC +10.0 0.4 400
600 1300 600 600 100 300 20 + 0.1 Cb1 600 1300
300
Minimum Differential Input Drive Reference Frequency Required Accuracy LVTTL DC INPUT CHARACTERISTICS Input High Voltage Input Low Voltage Input High Current Input Low Current LVTTL DC OUTPUT CHARACTERISTICS Output High Voltage Output Low Voltage
0 VCC 100 12.3 100 200
V V mV p-p MHz ppm V V A A V V
VIH VIL IIH, VIN = 2.4 V IIL, VIN = 0.4 V VOH, IOH = -2.0 mA VOL, IOL = 2.0 mA
2.0 0.8 5 -5 2.4 0.4
1
Cb = total capacitance of one bus line in pF. If mixed with Hs-mode devices, faster fall-times are allowed (see Table 6).
Rev.Pr A | Page 5 of 35
ADN2817/ADN2818
BIT ERROR RATE MONITOR (BERMON) SPECIFICATIONS
Preliminary Technical Data
TA = TMIN to TMAX, VCC = VMIN to VMAX, VEE = 0 V, CF = 0.47 uF, SLICEP = SLICEN = VEE, Input Data Pattern: PRBS 223 - 1, unless otherwise noted. Table 4.
Parameter BERMON Primary Mode BER Accuracy Conditions I2C Controlled Eye Profiling Input BER Range 1e-3 to 1e-12, Input DJ<0.4UI, DJ Ceiling>1e-2. Asymmetry <0.1UI. Requires external data processing algorithms to implement Q factor extrapolation. Number of data bits to collect pseudo-errors. User programmable in increment factors of 23 over the range 218 to 239. Min Typ +/-1 Max Unit Decades
Numbits
218
239
UI
Measurement Time Sample Phase Adjust Resolution BER Range Power Increase BERMON Secondary Mode BER Accuracy
Numbits/Datarate 6 5e-2 BER On BER Standby Analog Voltage Output Input BER Range 1e-3 to 1e-9, Input DJ=0 UI, DJ Ceiling>1e-2. Asymmetry =0 UI. BER is read as a voltage on pin VBER, when Automode = 0. Input BER Range 1e-3 to 1e-9, Input DJ=0.2 UI, DJ Ceiling>1e-2. Asymmetry =0 UI. BER is read as a voltage on pin VBER, when Automode = 0. Number of data bits to collect pseudo-errors. 2.5Gb/s 1Gb/s 155Mb/s 10Mb/s see Figure xx BER Automode 0.1 177 177 88 +/-1
s degrees BER mW mW Decades
BER Accuracy
+1/-2
Decades
Numbits Measurement Time
227 0.054 0.134 0.865 1.34 6 0.9
UI s s s s degrees V mW
Sample Phase Adjust Resolution VBER Power Increase
Rev. PrA | Page 6 of 35
Preliminary Technical Data ABSOLUTE MAXIMUM RATINGS
TA = TMIN to TMAX, VCC = VMIN to VMAX, VEE = 0 V, CF = 0.47 F, SLICEP = SLICEN = VEE, unless otherwise noted. Table 4.
Parameter Supply Voltage (VCC) Minimum Input Voltage (All Inputs) Maximum Input Voltage (All Inputs) Maximum Junction Temperature Storage Temperature Lead Temperature (Soldering 10 s) Rating 4.2 V VEE - 0.4 V VCC + 0.4 V 125C -65C to +150C 300C
ADN2817/ADN2818
Stress above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
THERMAL CHARACTERISTICS
Thermal Resistance
32-LFCSP, 4-layer board with exposed paddle soldered to VEE JA = 28C/W.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev.Pr A | Page 7 of 35
ADN2817/ADN2818 TIMING CHARACTERISTICS
CLKOUTP TH
Preliminary Technical Data
TS DATAOUTP/N
Figure 2. Output Timing
OUTP VCML OUTN OUTP-OUTN 0V
04228-0-004
VSE
VSE
VDIFF
Figure 3. Single-Ended vs. Differential Output Specifications
Rev. PrA | Page 8 of 35
04228-0-002
Preliminary Technical Data PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
32 VBER 31 VCC 30 VEE 29 DATAOU T P 28 DAT OU T N 27 SQU EL CH 26 CL K OU T P 25 CL K OU T N
ADN2817/ADN2818
Figure 4. Pin Configuration
Table 5. Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Exposed Pad
1
Mnemonic AUTOMODE VCC VREF NIN PIN SLICEP SLICEN VEE THRADJ REFCLKP REFCLKN VCC VEE CF2 CF1 LOL VEE VCC SADDR5 SCK SDA LOS VEE VCC CLKOUTN CLKOUTP SQUELCH DATAOUTN DATAOUTP VEE VCC VBER Pad
Type1 DI P AO AI AI AI AI P AI DI DI P P AO AO DO P P DI DI DI DO P P DO DO DI DO DO P P AO P
Description Set to Logic Low to enable analog voltage output mode for BER monitor Power for Limamp, LOS. Internal VREF Voltage. Decouple to GND with a 0.1 F capacitor. Differential Data Input. CML. Differential Data Input. CML. Differential Slice Level Adjust Input. Differential Slice Level Adjust Input. GND for Limamp, LOS. LOS Threshold Setting Resistor. Differential REFCLK Input. 12.3 MHz to 200 MHz. Differential REFCLK Input. 12.3 MHz to 200 MHz. VCO Power. VCO GND. Frequency Loop Capacitor. Frequency Loop Capacitor. Loss of Lock Indicator. LVTTL active high. FLL Detector GND. FLL Detector Power. Slave Address Bit 5. I2C Clock Input. I2C Data Input. Loss of Signal Detect Output. Active high. LVTTL. Output Buffer, I2C GND. Output Buffer, I2C Power. Differential Recovered Clock Output. CML. Differential Recovered Clock Output. CML. Disable Clock and Data Outputs. Active high. LVTLL. Differential Recovered Data Output. CML. Differential Recovered Data Output. CML. Phase Detector, Phase Shifter GND. Phase Detector, Phase Shifter Power. Relative BER monitor output. Referred to GND, Analog Voltage Output. Connect to GND
Type: P = power, AI = analog input, AO = analog output, DI = digital input, DO = digital output.
Rev.Pr A | Page 9 of 35
T H RAD J REFCL K P REFCL K N VCC VEE CF2 CF1 L OL
9 10 11 12 13 14 15 16
AU T OM OD E VCC VREF N IN PIN SL ICEP SL I CEN VEE
1 2 3 4 5 6 7 8
AD N 2817
24 23 22 21 20 19 18 17
VCC VEE L OS SDA SCK SAD D R5 VCC VEE
ADN2817/ADN2818 TYPICAL PERFORMANCE CHARACTERISTICS
16 14 12 10 8 6 4 2 1 10 100 RTH () 1k 10k
Preliminary Technical Data
1000 ADN2812 TOLERANCE SONET REQUIREMENT MASK SONET OBJECTIVE MASK EQUIPMENT LIMIT
JITTER AMPLITUDE (UI)
100
TRIP POINT (mV p-p)
10
1
04228-0-030
04228-0-003
0.1 1 10 100 1k 10k 100k 1M JITTER FREQUENCY (Hz) 10M
100k
100M
Figure 5. LOS Comparator Trip Point Programming
Figure 6. Typical Measured Jitter Tolerance OC-48
Rev. PrA | Page 10 of 35
Preliminary Technical Data I2C INTERFACE TIMING AND INTERNAL REGISTER DESCRIPTION
SLAVE ADDRESS [6...0] 1 MSB = 1 A5 SET BY PIN 19 0 0 0 0 0 R/W CTRL.
04228-0-005
ADN2817/ADN2818
X 0 = WR 1 = RD
Figure 7. Slave Address Configuration
S
SLAVE ADDR, LSB = 0 (WR) A(S) SUB ADDR A(S) DATA A(S)
DATA A(S)
P
Figure 8. I2C Write Data Transfer
S = START BIT A(S) = ACKNOWLEDGE BY SLAVE
P = STOP BIT A(M) = LACK OF ACKNOWLEDGE BY MASTER A(M) = ACKNOWLEDGE BY MASTER
Figure 9. I2C Read Data Transfer
START BIT
04228-0-007
S
SLAVE ADDR, LSB = 0 (WR) A(S) SUB ADDR A(S) S SLAVE ADDR, LSB = 1 (RD) A(S) DATA A(M)
04228-0-006
DATA A(M) P
SLAVE ADDRESS A6 A5
SUB ADDRESS A7 A0 D7
DATA D0
STOP BIT
SDA
S SLADDR[4...0]
WR
ACK SUB ADDR[6...1]
ACK DATA[6...1]
ACK
P
Figure 10. I2C Data Transfer Timing
tF
SDA
tSU;DAT tHD;STA tBUF tSU;STO tR
tR tLOW
SCK
tF
tHD;STA
S
tHIGH tHD;DAT
tSU;STA
S P S
Figure 11. I2C Port Timing Diagram
Rev.Pr A | Page 11 of 35
04228-0-009
04228-0-008
SCK
ADN2817/ADN2818
Table 6. Internal Register Map1
Reg Name FREQ0 FREQ1 FREQ2 RATE MISC CTRLA CTRLA_RD CTRLB CTRLB_RD CTRLC R/W R R R R R W R W R W ADDRESS D7 D6 0x0 MSB 0x1 MSB 0x2 0 MSB 0x3 COARSE_RD[8] MSB 0x4 0x8 0x5 0x9 0x6 0x11 0 CDR Bypass FDDI Mode Enable 0 HI_CODE[8] LO_CODE[8] 0 0 0 Disable DATA Buffer Config LOL Reset MISC[4] System Reset x FREF Range x D5 D4 D3
Preliminary Technical Data
D2 D1 D0 LSB LSB LSB Coarse Data Rate Readback COARSE_RD[1] datarate meas COARSE_RD[0] LOS status Static LOL LOL status x complete LSB Measure Data Lock to Data Rate/DIV FREF Ratio Rate Reference readback CTRLA 0 readback CTRLB Set Signal Degrade Threshold Disable CLK Buffer Subharmonic Ratio Acq Mode Cont Rate / Single Rate Datarate Range Enable Signal Degrade LOS forces acquisition Initiate PRBS Sequence Config LOS Squelch Mode Boost Output Reset MISC[2] 0 0 0
CTRLD FDDI_MODE SEL_MODE HI_CODE LO_CODE CODE_LSB BERCTLA BERCTLB BERSTS
W W W W W W W W R
0x22 0x0D 0x34 0x35 0x36 0x39 0x1E 0x1F 0x20
PRBS Mode[2..0] 0 CLK Holdover CLK Holdover Mode 2A Mode 2B 0 0 HI_CODE[1] LO_CODE[1] LO_CODE[0]
0 x
BER_RES R 0x21 BER_DAC R 0x24 PHASE W 0x37 1 All writeable registers default to 0x00.
0 HI_CODE[0] 0 BER Start Error Count Byte Select, e.g. 011=Byte 3 of 5 BER Timer Pulse Enable Clock XOR 0 BER Mode BER Input BER Meas x x x x x x Status BER_RES[7..0], BER Measurement Result BER_DAC[7..0], Output of BER DAC PHASE[7..0], 2's Complement Sample Phase Offset Adjustment 0 0 0 Phase Polarity BER Stdby Mode
Table 7. Miscellaneous Register, MISC
LOS Status D5 0 = No loss of signal 1 = Loss of signal Static LOL D4 0 = Waiting for next LOL 1 = Static LOL until reset LOL Status D3 0 = Locked 1 = Acquiring Datarate Measurement Complete D2 0 = Measuring datarate 1 = Measurement complete Coarse Rate Readback LSB D0 COARSE_RD[0]
D7 x
D6 x
D1 x
Table 8. Control Register, CTRLA1
FREF Range D7 D6 0 0 0 1 1 0 1 1 Datarate/Div_FREF Ratio D5 D4 D3 D2 0 0 0 0 0 0 0 1 0 0 1 0 n 1 0 0 0 Measure Datarate D1 Set to 1 to measure datarate Lock to Reference D0 0 = Lock to input data 1 = Lock to reference clock
12.3 MHz to 25 MHz 25 MHz to 50 MHz 50 MHz to 100 MHz 100 MHz to 200 MHz
1 2 4 2n 256
1
Where DIV_FREF is the divided down reference referred to the 12.3 MHz to 25 MHz band (see the Reference Clock (Optional) section).
Rev. PrA | Page 12 of 35
Preliminary Technical Data
Table 9. Control Register, CTRLB
Config LOL D7 0 = LOL pin normal operation 1 = LOL pin is static LOL Reset MISC[4] D6 Write a 1 followed by 0 to reset MISC[4] System Reset D5 Write a 1 followed by 0 to reset ADN2817/ADN2818 D4 Set to 0
ADN2817/ADN2818
Reset MISC[2] D3 Write a 1 followed by 0 to reset MISC[2]
D2 Set to 0
D1 Set to 0
D0 Set to 0
Table 10. Control Register, CTRLC
D7 Set to 0 D6 Set to 0 Signal Degrade Threshold D5 0=Set SD Threshold to 9mV 1=Set SD Threshold to 1.9x LOS Threshold Signal Degrade Mode D4 0= Disable Signal Degrade Mode 1= Enable Signal Degrade Mode D3 Set to 0 Config LOS D2 0 = Active high LOS 1 = Active low LOS Squelch Mode D1 0 = Squelch CLK and DATA 1 = Squelch CLK or DATA D0 Set to 0
Table 111. Control Register, CTRLD
CDR Bypass D7 0=CDR Enabled 1=CDR Disabled Disable DATA Buffer D6 0=Data Buffer Enabled 1=Data Buffer Disabled Disable CLK Buffer D5 0=CLK Buffer Enabled 1=CLK Buffer Disabled Initiate PRBS D3 Write a 1 followed by 0 to initiate PRBS Generate Sequence PRBS Mode D2 0 0 0 0 1 D1 0 0 1 1 0 D0 0 1 0 1 0 Power Down Generate Mode Detect Mode, compares errors Detect Mode, O/P to BER only Detect mode, BER not in use
D4 Set to 0
Table 12. FDDI_MODE
FDDI Enable D7 0= FDDI Mode Disabled 1= FDDI Mode Enabled Subharmonic Ratio [6..2] D6 D5 D4 D3 D2 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 --------------------1 1 1 1 1 D1 Set to 0 D0 Set to 0
=1 =2 =3 = 31
Table 13. SEL_MODE
Mode Control 2 D5 0=LTD/LTR Mode 1=LTR Mode Only Mode Control 1 D4 0= Continuous Rate 1= Single Rate Mode Control 0 D3 0= Full Range (12.3M2.7G) 1= Limited Range Clock Holdover Mode 2A D2 Set to 1 for Clock Holdover Mode 2A Clock Holdover Mode 2B D1 Set to 1 for Clock Holdover Mode 2B
D7 Set to 0
D6 Set to 0
D0 Set to 0
Rev.Pr A | Page 13 of 35
ADN2817/ADN2818
Table 14. BERCTLA
Set BER Timer D7 D6 D5 0 0 0 = 218 bits 0 0 1 = 221 bits 0 1 0 = 224 bits 0 1 1 = 227 bits 1 0 0 = 230 bits 1 0 1 = 233 bits 1 1 0 = 236 bits 1 1 1 = 239 bits Phase Polarity D4 0= Positive 1= Negative BER Start Pulse D3 Write a "1" followed by "0" to initiate BER measurement
Preliminary Technical Data
Error Count Byte Select D2 D1 D0 0 0 0 = Byte 0 0 0 1 = Byte 1 0 1 0 = Byte 2 0 1 1 = Byte 3 1 0 0 = Byte 4 1 0 1 = Byte 5
Table 15. BERCTLB
D7 Set to 0 D6 Set to 0 Enable BER D5 0= BER Disabled 1= BER Enabled BER Standby Mode D4 0= BER meas enabled 1= BER meas in Stdby mode Clock XOR Input D3 Write a "1" followed by "0" to clock input to XOR BER Mode D2 D1 D0 0 0 0 = NDC -> OB 0 0 1 = DDC -> OB 0 1 0 = DIV0 -> OB 0 1 1 = DIV1 -> OB 1 0 0 = CLK0,1 -> OB 1 0 1 = NDC -> PRBS 1 1 0 = DDC -> PRBS
Rev. PrA | Page 14 of 35
Preliminary Technical Data TERMINOLOGY
Input Sensitivity and Input Overdrive Sensitivity and overdrive specifications for the quantizer involve offset voltage, gain, and noise. The relationship between the logic output of the quantizer and the analog voltage input is shown in Figure 12. For sufficiently large positive input voltage, the output is always Logic 1 and, similarly for negative inputs, the output is always Logic 0. However, the transitions between output Logic Levels 1 and 0 are not at precisely defined input voltage levels, but occur over a range of input voltages. Within this range of input voltages, the output might be either 1 or 0, or it might even fail to attain a valid logic state. The width of this zone is determined by the input voltage noise of the quantizer. The center of the zone is the quantizer input offset voltage. Input overdrive is the magnitude of signal required to guarantee the correct logic level with 1 x 10-10 confidence level.
OUTPUT 1 NOISE
ADN2817/ADN2818
10mVp-p VREF scope probe PIN
+ Quantizer 50 VREF 3k 50 2.5V
Figure 13. Single-Ended Sensitivity Measurement
0
OFFSET OVERDRIVE SENSITIVITY (2x OVERDRIVE)
INPUT (V p-p)
Driving the ADN2817/ADN2818 differentially (see Figure 14), sensitivity seems to improve from observing the quantizer input with an oscilloscope probe. This is an illusion caused by the use of a single-ended probe. A 5 mV p-p signal appears to drive the ADN2817/ADN2818 quantizer. However, the single-ended probe measures only half the signal. The true quantizer input signal is twice this value, because the other quantizer input is a complementary signal to the signal being observed.
5mV p-p VREF SCOPE PROBE
04228-0-010
Figure 12. Input Sensitivity and Input Overdrive
PIN
+ QUANTIZER
Single-Ended vs. Differential AC coupling is typically used to drive the inputs to the quantizer. The inputs are internally dc biased to a commonmode potential of ~2.5 V. Driving the ADN2817/ADN2818 single-ended and observing the quantizer input with an oscilloscope probe at the point indicated in Figure 13 shows a binary signal with an average value equal to the common-mode potential and instantaneous values both above and below the average value. It is convenient to measure the peak-to-peak amplitude of this signal and call the minimum required value the quantizer sensitivity. Referring to Figure 13, because both positive and negative offsets need to be accommodated, the sensitivity is twice the overdrive. The ADN2817/ADN2818 quantizer typically has 6 mV p-p sensitivity.
NIN
-
50 VREF 5mV p-p VREF
50 2.5V 3k
Figure 14. Differential Sensitivity Measurement
LOS Response Time LOS response time is the delay between removal of the input signal and indication of loss of signal (LOS) at the LOS output, Pin 22. When the inputs are dc-coupled, the LOS assert time of the AD2817 is 500 ns typically and the de-assert time is 400 ns typically,. In practice, the time constant produced by the ac coupling at the quantizer input and the 50 on-chip input termination determines the LOS response time.
Rev.Pr A | Page 15 of 35
04228-0-012
ADN2817/ADN2818 JITTER SPECIFICATIONS
The ADN2817/ADN2818 CDR is designed to achieve the best bit-error-rate (BER) performance and exceeds the jitter transfer, generation, and tolerance specifications proposed for SONET/SDH equipment defined in the Telcordia Technologies specification. Jitter is the dynamic displacement of digital signal edges from their long-term average positions, measured in unit intervals (UI), where 1 UI = 1 bit period. Jitter on the input data can cause dynamic phase errors on the recovered clock sampling edge. Jitter on the recovered clock causes jitter on the retimed data. The following sections briefly summarize the specifications of jitter generation, transfer, and tolerance in accordance with the Telcordia document (GR-253-CORE, Issue 3, September 2000) for the optical interface at the equipment level and the ADN2817/ADN2818 performance with respect to those specifications.
0.1
Preliminary Technical Data
JITTER GAIN (dB)
SLOPE = -20dB/DECADE ACCEPTABLE RANGE
fC
JITTER FREQUENCY (kHz)
Figure 15. Jitter Transfer Curve
JITTER TOLERANCE
The jitter tolerance is defined as the peak-to-peak amplitude of the sinusoidal jitter applied on the input signal, which causes a 1 dB power penalty. This is a stress test intended to ensure that no additional penalty is incurred under the operating conditions (see Figure 16).
15.00
INPUT JITTER AMPLITUDE (UI p-p)
JITTER GENERATION
The jitter generation specification limits the amount of jitter that can be generated by the device with no jitter and wander applied at the input. For OC-48 devices, the band-pass filter has a 12 kHz high-pass cutoff frequency with a roll-off of 20 dB/decade, and a low-pass cutoff frequency of at least 20 MHz. The jitter generated must be less than 0.01 UI rms, and must be less than 0.1 UI p-p.
SLOPE = -20dB/DECADE
1.50
JITTER TRANSFER
The jitter transfer function is the ratio of the jitter on the output signal to the jitter applied on the input signal versus the frequency. This parameter measures the limited amount of the jitter on an input signal that can be transferred to the output signal (see Figure 15).
0.15
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f0
f1
f2
f3
f4
JITTER FREQUENCY (kHz)
Figure 16. SONET Jitter Tolerance Mask
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04228-0-014
Preliminary Technical Data THEORY OF OPERATION
The ADN2817/ADN2818 is a delay- and phase-locked loop circuit for clock recovery and data retiming from an NRZ encoded data stream. The phase of the input data signal is tracked by two separate feedback loops, which share a common control voltage. A high speed delay-locked loop path uses a voltage controlled phase shifter to track the high frequency components of input jitter. A separate phase control loop, comprised of the VCO, tracks the low frequency components of input jitter. The initial frequency of the VCO is set by yet a third loop, which compares the VCO frequency with the input data frequency and sets the coarse tuning voltage. The jitter tracking phase-locked loop controls the VCO by the fine-tuning control. The delay- and phase-loops together track the phase of the input data signal. For example, when the clock lags input data, the phase detector drives the VCO to higher frequency, and also increases the delay through the phase shifter; both these actions serve to reduce the phase error between the clock and data. The faster clock picks up phase, while the delayed data loses phase. Because the loop filter is an integrator, the static phase error is driven to zero. Another view of the circuit is that the phase shifter implements the zero required for frequency compensation of a second-order phase-locked loop, and this zero is placed in the feedback path and, thus, does not appear in the closed-loop transfer function. Jitter peaking in a conventional second-order phase-locked loop is caused by the presence of this zero in the closed-loop transfer function. Because this circuit has no zero in the closed-loop transfer, jitter peaking is minimized. The delay- and phase-loops together simultaneously provide wide-band jitter accommodation and narrow-band jitter filtering. The linearized block diagram in Figure 17 shows that the jitter transfer function, Z(s)/X(s), is a second-order low-pass providing excellent filtering. Note that the jitter transfer has no zero, unlike an ordinary second-order phase-locked loop. This means that the main PLL loop has virtually zero jitter peaking (see Figure 18). This makes this circuit ideal for signal regenerator applications, where jitter peaking in a cascade of regenerators can contribute to hazardous jitter accumulation. The error transfer, e(s)/X(s), has the same high-pass form as an ordinary phase-locked loop. This transfer function is free to be optimized to give excellent wide-band jitter accommodation, because the jitter transfer function, Z(s)/X(s), provides the narrow-band jitter filtering.
psh INPUT DATA X(s) e(s) d/sc
ADN2817/ADN2818
o/s
Z(s) RECOVERED CLOCK d = PHASE DETECTOR GAIN o = VCO GAIN c = LOOP INTEGRATOR psh = PHASE SHIFTER GAIN n = DIVIDE RATIO
1/n
JITTER TRANSFER FUNCTION Z(s) 1 = X(s) n psh cn +1 +s s2 o do TRACKING ERROR TRANSFER FUNCTION e(s) s2 = d psh do X(s) + s2 + s c cn
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Figure 17. ADN2817/ADN2818 PLL/DLL Architecture
JITTER PEAKING IN ORDINARY PLL
JITTER GAIN (dB)
ADN2812 Z(s) X(s)
o n psh
d psh c
FREQUENCY (kHz)
Figure 18. ADN2817/ADN2818 Jitter Response vs. Conventional PLL
The delay- and phase-loops contribute to overall jitter accommodation. At low frequencies of input jitter on the data signal, the integrator in the loop filter provides high gain to track large jitter amplitudes with small phase error. In this case, the VCO is frequency modulated and jitter is tracked as in an ordinary phase-locked loop. The amount of low frequency jitter that can be tracked is a function of the VCO tuning range. A wider tuning range gives larger accommodation of low frequency jitter. The internal loop control voltage remains small for small phase errors, so the phase shifter remains close to the center of its range and thus contributes little to the low frequency jitter accommodation.
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ADN2817/ADN2818
At medium jitter frequencies, the gain and tuning range of the VCO are not large enough to track input jitter. In this case, the VCO control voltage becomes large and saturates, and the VCO frequency dwells at one extreme of its tuning range or the other. The size of the VCO tuning range, therefore, has only a small effect on the jitter accommodation. The delay-locked loop control voltage is now larger, and so the phase shifter takes on the burden of tracking the input jitter. The phase shifter range, in UI, can be seen as a broad plateau on the jitter tolerance curve. The phase shifter has a minimum range of 2 UI at all data rates. The gain of the loop integrator is small for high jitter frequencies, so that larger phase differences are needed to make the loop control voltage big enough to tune the range of the phase shifter. Large phase errors at high jitter frequencies
Preliminary Technical Data
cannot be tolerated. In this region, the gain of the integrator determines the jitter accommodation. Because the gain of the loop integrator declines linearly with frequency, jitter accommodation is lower with higher jitter frequency. At the highest frequencies, the loop gain is very small, and little tuning of the phase shifter can be expected. In this case, jitter accommodation is determined by the eye opening of the input data, the static phase error, and the residual loop jitter generation. The jitter accommodation is roughly 0.5 UI in this region. The corner frequency between the declining slope and the flat region is the closed loop bandwidth of the delay-locked loop, which is roughly 3 MHz at OC-48.
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Preliminary Technical Data FUNCTIONAL DESCRIPTION
FREQUENCY ACQUISITION
The ADN2817/ADN2818 acquires frequency from the data over a range of data frequencies from 12.3 Mb/s to 2.7 Gb/s. The lock detector circuit compares the frequency of the VCO and the frequency of the incoming data. When these frequencies differ by more than 1000 ppm, LOL is asserted. This initiates a frequency acquisition cycle. The VCO frequency is reset to the bottom of its range, which is 12.3 MHz. The frequency detector then compares this VCO frequency and the incoming data frequency and increments the VCO frequency, if necessary. Initially, the VCO frequency is incremented in large steps to aid fast acquisition. As the VCO frequency approaches the data frequency, the step size is reduced until the VCO frequency is within 250 ppm of the data frequency, at which point LOL is de-asserted. Once LOL is de-asserted, the frequency-locked loop is turned off. The PLL/DLL pulls in the VCO frequency the rest of the way until the VCO frequency equals the data frequency. The frequency loop requires a single external capacitor between CF1 and CF2, Pins 14 and 15. A 0.47 F 20%, X7R ceramic chip capacitor with < 10 nA leakage current is recommended. Leakage current of the capacitor can be calculated by dividing the maximum voltage across the 0.47 F capacitor, ~3 V, by the insulation resistance of the capacitor. The insulation resistance of the 0.47 uF capacitor should be greater than 300 M.
LOL 1
ADN2817/ADN2818
-1000
-250
0
250
1000
fVCO ERROR (ppm)
Figure 19. Transfer Function of LOL
LOL Detector Operation Using a Reference Clock
In this mode, a reference clock is used as an acquisition aid to lock the ADN2817/ADN2818 VCO. Lock to reference mode is enabled by setting CTRLA[0] to 1. The user also needs to write to the CTRLA[7:6] and CTRLA[5:2] bits in order to set the reference frequency range and the divide ratio of the data rate with respect to the reference frequency. For more details, see the Reference Clock (Optional) section. In this mode, the lock detector monitors the difference in frequency between the divided down VCO and the divided down reference clock. The loss of lock signal, which appears on the LOL Pin 16, is deasserted when the VCO is within 250 ppm of the desired frequency. This enables the D/PLL, which pulls the VCO frequency in the remaining amount with respect to the input data and also acquires phase lock. Once locked, if the input frequency error exceeds 1000 ppm (0.1%), the loss of lock signal is re-asserted and control returns to the frequency loop, which re-acquires with respect to the reference clock. The LOL pin remains asserted until the VCO frequency is within 250 ppm of the desired frequency. This hysteresis is shown in Figure 19.
LOCK DETECTOR OPERATION
The lock detector on the ADN2817/ADN2818 has three modes of operation: normal mode, REFCLK mode, and static LOL mode.
Static LOL Mode
The ADN2817/ADN2818 implements a static LOL feature, which indicates if a loss of lock condition has ever occurred and remains asserted, even if the ADN2817/ADN2818 regains lock, until the static LOL bit is manually reset. The I2C register bit, MISC[4], is the static LOL bit. If there is ever an occurrence of a loss of lock condition, this bit is internally asserted to logic high. The MISC[4] bit remains high even after the ADN2817/ADN2818 has re-acquired lock to a new data rate. This bit can be reset by writing a 1 followed by 0 to I2C Register Bit CTRLB[6]. Once reset, the MISC[4] bit remains de-asserted until another loss of lock condition occurs. Writing a 1 to I2C Register Bit CTRLB[7] causes the LOL pin, Pin 16, to become a static LOL indicator. In this mode, the LOL pin mirrors the contents of the MISC[4] bit and has the functionality described in the previous paragraph. The CTRLB[7] bit defaults to 0. In this mode, the LOL pin operates in the normal operating mode, that is, it is asserted only when the ADN2817/ADN2818 is in acquisition mode and de-asserts when the ADN2817/ADN2818 has re-acquired lock.
Normal Mode
In normal mode, the ADN2817/ADN2818 is a continuous rate CDR that locks onto any data rate from 12.3 Mb/s to 2.7 Gb/s without the use of a reference clock as an acquisition aid. In this mode, the lock detector monitors the frequency difference between the VCO and the input data frequency, and de-asserts the loss of lock signal, which appears on LOL Pin 16, when the VCO is within 250 ppm of the data frequency. This enables the D/PLL, which pulls the VCO frequency in the remaining amount and also acquires phase lock. Once locked, if the input frequency error exceeds 1000 ppm (0.1%), the loss of lock signal is re-asserted and control returns to the frequency loop, which begins a new frequency acquisition starting at the lowest point in the VCO operating range, 12.3 MHz. The LOL pin remains asserted until the VCO locks onto a valid input data stream to within 250 ppm frequency error. This hysteresis is shown in Figure 19.
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ADN2817/ADN2818
HARMONIC DETECTOR
The ADN2817/ADN2818 provides a harmonic detector, which detects whether or not the input data has changed to a lower harmonic of the data rate that the VCO is currently locked onto. For example, if the input data instantaneously changes from OC-48, 2.488 Gb/s, to an OC-12, 622.080 Mb/s bit stream, this could be perceived as a valid OC-48 bit stream, because the OC-12 data pattern is exactly 4x slower than the OC-48 pattern. So, if the change in data rate is instantaneous, a 101 pattern at OC-12 would be perceived by the ADN2817/ADN2818 as a 111100001111 pattern at OC-48. If the change to a lower harmonic is instantaneous, a typical CDR could remain locked at the higher data rate. The ADN2817/ADN2818 implements a harmonic detector that automatically identifies whether or not the input data has switched to a lower harmonic of the data rate that the VCO is currently locked onto. When a harmonic is identified, the LOL pin is asserted and a new frequency acquisition is initiated. The ADN2817/ADN2818 automatically locks onto the new data rate, and the LOL pin is de-asserted. However, the harmonic detector does not detect higher harmonics of the data rate. If the input data rate switches to a higher harmonic of the data rate the VCO is currently locked onto, the VCO loses lock, the LOL pin is asserted, and a new frequency acquisition is initiated. The ADN2817/ADN2818 automatically locks onto the new data rate. The time to detect lock to harmonic is 16,384 x (Td/) where: 1/Td is the new data rate. For example, if the data rate is switched from OC-48 to OC-12, then Td = 1/622 MHz. is the data transition density. Most coding schemes seek to ensure that = 0.5, for example, PRBS, 8B/10B. When the ADN2817/ADN2818 is placed in lock to reference mode, the harmonic detector is disabled.
Preliminary Technical Data
SLICE AND SAMPLE PHASE ADJUST (ADN2817 ONLY)
The quantizer slicing level can be offset by 100 mV to mitigate the effect of amplified spontaneous emission (ASE) noise or duty cycle distortion by applying a differential voltage input of up to 0.95 V to SLICEP/N inputs. If no adjustment of the slice level is needed, SLICEP/N should be tied to VEE. The gain of the slice adjustment is ~0.1 V/V. If the user is not using the BER monitoring function, sample phase adjustment can be utilized to optimize the horizontal sampling point of the incoming data eye. The ADN2817 automatically centers the sampling point to the best of its ability. However, sample phase adjustment could be used to compensate for any static phase offset of the CDR and duty cycle distortion of the incoming eye. Sample phase adjustment is applied to the incoming eye via the PHASE register. It is important to note that sample phase adjustment can not be used if the user is utilising the BER monitoring capability. This is because the BER monitoring circuit requires control of the sample phase adjustment circuitry. Also, using the sample phase adjustment capability uses an additional 180mW of power.
LOSS OF SIGNAL (LOS) DETECTOR (ADN2817 ONLY)
The receiver front end LOS detector circuit detects when the input signal level has fallen below a user-adjustable threshold. The threshold is set with a single external resistor from Pin 9, THRADJ, to VEE. The LOS comparator trip point-versusresistor value is illustrated in Figure 5. If the input level to the ADN2817/ADN2818 drops below the programmed LOS threshold, the output of the LOS detector, LOS Pin 22, is asserted to a Logic 1. The LOS detector's response time is ~500 ns by design, but is dominated by the RC time constant in accoupled applications. The LOS pin defaults to active high. However, by setting Bit CTRLC[2] to 1, the LOS pin is configured as active low. There is typically 6 dB of electrical hysteresis designed into the LOS detector to prevent chatter on the LOS pin. This means that, if the input level drops below the programmed LOS threshold causing the LOS pin to assert, the LOS pin is not deasserted until the input level has increased to 6 dB (2x) above the LOS threshold (see Figure 20).
LIMITING AMPLIFIER (ADN2817 ONLY)
The limiting amplifier on the ADN2817 has differential inputs (PIN/NIN), which are internally terminated with 50 to an on-chip voltage reference (VREF = 2.5 V typically). The inputs are typically ac-coupled externally, although dc coupling is possible as long as the input common mode voltage remains above 2.5 V (see Figure 28, Figure 29, and Figure 30 in the Applications Information section). Input offset is factory trimmed to achieve better than 6 mV typical sensitivity with minimal drift. The limiting amplifier can be driven differentially or single-ended.
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Preliminary Technical Data
LOS OUTPUT INPUT VOLTAGE (VDIFF)
ADN2817/ADN2818
R/W bit). The bits are transferred from MSB to LSB. 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. All other devices withdraw from the bus at this point and maintain an idle condition. The idle condition is where the device monitors the SDA and SCK lines waiting for the start condition and correct transmitted address. 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. The ADN2817/ADN2818 acts as a standard slave device on the bus. The data on the SDA pin is 8 bits long supporting the 7-bit addresses plus the R/W bit. The ADN2817/ADN2818 has 8 subaddresses to enable the user-accessible internal registers (see Table 1 through Table 7). It, therefore, interprets the first byte as the device address and the second byte as the starting subaddress. Autoincrement 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. 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, then they cause an immediate jump to the idle condition. During a given SCK high period, the user should issue one start condition, one stop condition, or a single stop condition followed by a single start condition. If an invalid subaddress is issued by the user, the ADN2817/ADN2818 does not issue an acknowledge and returns to the idle condition. If the user exceeds the highest subaddress while reading back in autoincrement mode, then 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 SDATA line is not pulled low on the ninth pulse. See Figure 8 and Figure 9 for sample read and write data transfers and Figure 10 for a more detailed timing diagram.
INPUT LEVEL
HYSTERESIS
LOS THRESHOLD
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t
Figure 20. ADN2817 LOS Detector Hysteresis
The LOS detector and the SLICE level adjust can be used simultaneously on the ADN2817/ADN2818. This means that any offset added to the input signal by the SLICE adjust pins does not affect the LOS detector's measurement of the absolute input level.
SQUELCH MODE
Two squelch modes are available with the ADN2817/ADN2818. Squelch DATAOUT AND CLKOUT mode is selected when CTRLC[1] = 0 (default mode). In this mode, when the squelch input, Pin 27, is driven to a TTL high state, both the clock and data outputs are set to the zero state to suppress downstream processing. If the squelch function is not required, Pin 27 should be tied to VEE. Squelch DATAOUT OR CLKOUT mode is selected when CTRLC[1] is 1. In this mode, when the squelch input is driven to a high state, the DATAOUT pins are squelched. When the squelch input is driven to a low state, the CLKOUT pins are squelched. This is especially useful in repeater applications, where the recovered clock may not be needed.
I2C INTERFACE
The ADN2817/ADN2818 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 connected to the bus. Each slave device is recognized by a unique address. The ADN2817/ADN2818 has two possible 7bit slave addresses for both read and write operations. The MSB of the 7-bit slave address is factory programmed to 1. B5 of the slave address is set by Pin 19, SADDR5. Slave address bits [4:0] are defaulted to all 0s. The slave address consists of the 7 MSBs of an 8-bit word. The LSB of the word sets either a read or write operation (see Figure 7). Logic 1 corresponds to a read operation, while Logic 0 corresponds to a write operation. To control the device on the bus, the following protocol must be followed. First, the master initiates a data transfer by establishing a start condition, defined by a high to low transition on SDA while SCK remains high. This indicates that an address/data stream follows. All peripherals respond to the start condition and shift the next eight bits (the 7-bit address and the
REFERENCE CLOCK (OPTIONAL)
A reference clock is not required to perform clock and data recovery with the ADN2817/ADN2818. 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 being used, then REFCLKP should be tied to VCC, and REFCLKN can be left floating or tied to VEE (the inputs are internally terminated to VCC/2). See Figure 21 through Figure 23 for sample configurations. The REFCLK input buffer accepts any differential signal with a
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ADN2817/ADN2818
peak-to-peak differential amplitude of greater than 100 mV (for example, LVPECL or LVDS) or a standard single-ended low voltage TTL input, providing maximum system flexibility. Phase noise and duty cycle of the reference clock are not critical and 100 ppm accuracy is sufficient.
ADN2817/18 REFCLKP 10 11 REFCLKN
100k 100k
Preliminary Technical Data
not supported.
Using the Reference Clock to Lock onto Data
In this mode, the ADN2817/ADN2818 locks onto a frequency derived from the reference clock according to the following equation: Data Rate/2CTRLA[5:2] = REFCLK/2CTRLA[7:6] The user must know exactly what the data rate is, and provide a reference clock that is a function of this rate. The ADN2817/ADN2818 can still be used as a continuous rate device in this configuration, provided that the user has the ability to provide a reference clock that has a variable frequency (see Application Note AN-632). The reference clock can be anywhere between 12.3 MHz and 200 MHz. By default, the ADN2817/ADN2818 expects a reference clock of between 12.3 MHz and 25 MHz. If it is between 25 MHz and 50 MHz, 50 MHz and 100 MHz, or 100 MHz and 200 MHz, the user needs to configure the ADN2817/ADN2818 to use the correct reference frequency range by setting two bits of the CTRLA register, CTRLA[7:6]. Table 12. CTRLA Settings
CTRLA[7:6] 00 01 10 11 Range (MHz) 12.3 to 25 25 to 50 50 to 100 100 to 200 CTRLA[5:2] 0000 0001 n 1000 Ratio 1 2 2n 256
Buffer
VCC/2
Figure 21. Differential REFCLK Configuration
VCC CLK OSC REFCLKP
OUT
ADN2817/18
10 Buffer
REFCLKN x 11
100k
100k
VCC/2
Figure 22. Single-Ended REFCLK Configuration
VCC 10 REFCLKP Buffer NC 11 REFCLKN
100k 100k
ADN2817/18
VCC/2
Figure 23. No REFCLK Configuration
The user can specify a fixed integer multiple of the reference clock to lock onto using CTRLA[5:2], where CTRLA should be set to the data rate/DIV_FREF, where DIV_FREF represents the divided-down reference referred to the 12.3 MHz to 25 MHz band. For example, if the reference clock frequency was 38.88 MHz and the input data rate was 622.08 Mb/s, then CTRLA[7:6] would be set to [01] to give a divided-down reference clock of 19.44 MHz. CTRLA[5:2] would be set to [0101], that is, 5, because 622.08 Mb/s/19.44 MHz = 25
The two uses of the reference clock are mutually exclusive. The reference clock can be used either as an acquisition aid for the ADN2817/ADN2818 to lock onto data, or to measure the frequency of the incoming data to within 0.01%. (There is the capability to measure the data rate to approximately 10% without the use of a reference clock.) The modes are mutually exclusive, because, in the first use, the user knows exactly what the data rate is and wants to force the part to lock onto only that data rate; in the second use, the user does not know what the data rate is and wants to measure it. Lock to reference mode is enabled by writing a 1 to I2C Register Bit CTRLA[0]. Fine data rate readback mode is enabled by writing a 1 to I2C Register Bit CTRLA[1]. Writing a 1 to both of these bits at the same time causes an indeterminate state and is
In this mode, if the ADN2817/ADN2818 loses lock for any reason, it relocks onto the reference clock and continues to output a stable clock. While the ADN2817/ADN2818 is operating in lock to reference mode, if the user ever changes the reference frequency, the FREF range (CTRLA[7:6]), or the FREF ratio (CTRLA[5:2]), this must be followed by writing a 0 to 1 transition into the CTRLA[0] bit to initiate a new lock to reference command.
Using the Reference Clock to Measure Data Frequency
The user can also provide a reference clock to measure the recovered data frequency. In this case, the user provides a reference clock, and the ADN2817/ADN2818 compares the frequency of the incoming data to the incoming reference clock
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Preliminary Technical Data
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 of the ADN2817/ADN2818 data rate measurement. For example, if a 100-ppm accuracy reference clock is used, the total accuracy of the measurement is within 200 ppm. The reference clock can range from 12.3 MHz and 200 MHz. The ADN2817/ADN2818 expects a reference clock between 12.3 MHz and 25 MHz by default. If it is between 25 MHz and 50 MHz, 50 MHz and 100 MHz, or 100 MHz and 200 MHz, the user needs to configure the ADN2817/ADN2818 to use the correct reference frequency range by setting two bits of the CTRLA register, CTRLA[7:6]. Using the reference clock to determine the frequency of the incoming data does not affect the manner in which the part locks onto data. In this mode, the reference clock is used only to determine the frequency of the data. For this reason, the user does not need to know the data rate to use the reference clock in this manner. Prior to reading back the data rate using the reference clock, the CTRLA[7:6] bits must be set to the appropriate frequency range with respect to the reference clock being used. A fine data rate readback is then executed as follows: Step 1: Write a 1 to CTRLA[1]. This enables the fine data rate measurement capability of the ADN2817/ADN2818. This bit is level sensitive and does not need to be reset to perform subsequent frequency measurements. Step 2: Reset MISC[2] by writing a 1 followed by a 0 to CTRLB[3]. This initiates a new data rate measurement. Step 3: Read back MISC[2]. If it is 0, then the measurement is not complete. If it is 1, then the measurement is complete and the data rate can be read back on FREQ[22:0]. The time for a data rate measurement is typically 80 ms. Step 4: Read back the data rate from registers FREQ2[6:0], FREQ1[7:0], and FREQ0[7:0]. Use the following equation to determine the data rate:
ADN2817/ADN2818
For example, if the reference clock frequency is 32 MHz, SEL_RATE = 1, since the CTRLA[7:6] setting would be [01], because the reference frequency would fall into the 25 MHz to 50 MHz range. Assume for this example that the input data rate is 2.488 Gb/s (OC-48). After following Steps 1 through 4, the value that is read back on FREQ[22:0] = 0x26E010, which is equal to 2.5477 x 106. Plugging this value into the equation yields
(2.5477e6 x 32e6)/(2 (14+1) ) = 2.488 Gb/s
If subsequent frequency measurements are required, CTRLA[1] should remain set to 1. It does not need to be reset. The measurement process is reset by writing a 1 followed by a 0 to CTRLB[3]. This initiates a new data rate measurement. Follow Steps 2 through 4 to read back the new data rate. Note: A data rate readback is valid only if LOL is low. If LOL is high, the data rate readback is invalid.
f DATARATE = (FREQ [22..0]x f REFCLK )/ 2 (14 + SEL _ RATE ) where: FREQ[22:0] is the reading from FREQ2[6:0] (MSByte), FREQ1[7:0], and FREQ0[7:0] (LSByte).
Table 13.
D22 D21...D17 D16 D15 D14...D9 D8 D7 D6...D1 D0
FREQ2[6:0]
FREQ1[7:0]
FREQ0[7:0]
fDATARATE is the data rate (Mb/s). fREFCLK is the REFCLK frequency (MHz). SEL_RATE is the setting from CTRLA[7:6].
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ADN2817/ADN2818
Additional Features Available via the I2C Interface Coarse Data Rate Readback
The data rate can be read back over the I2C interface to approximately +10% without the need of an external reference clock. A 9-bit register, COARSE_RD[8:0], can be read back when LOL is de-asserted. The 8 MSBs of this register are the contents of the RATE[7:0] register. The LSB of the COARSE_RD register is Bit MISC[0]. Table 14 provides coarse data rate readback to within 10%.
Preliminary Technical Data
mode and BER On mode without loosing lock. This is because we must route the NDC clock signal through different circuitry in going from one mode to the other. Switching between BER Standby mode and BER On mode is achieved without interrupting the data recovery. The incremental power between BER Off and BER Standby mode is 88mW, and that between BER Off and BER On modes is 177mW. BER On Mode The BER On mode of operation allows the user to scan the incoming data eye in the time dimension and build up a profile of the BER statistics. User Protocol User Powers Up BER Circuitry, through I2C. User initiates BER measurement. Sample Phase Offset & Number of data bits to be counted (Numbits - choice between 2^18, 2^21, 2^24, 2^27, 2^30, 2^33, 2^36 or 2^39) are supplied by user, through I2C. Apply Reset Pulse to BER through I2C. BER Logic indicates End Of BER Measurement with EOBM signal and updates the number of counted errors on NumErrors<39:0> User must poll the I2C to determine if EOBM has been asserted. User reads back NumErrors<39:0>, through the I2C. BER for programmed sample phase is calculated as Numerrors/Numbits. User Powers Down BER, or requests another BER measurement (step 2). The user will sweep the phase over 0 to 1 UI, to get the BER profile required. Note: The ADN2817 does not output the BER at the normal decision instant. It outputs pseudo-BER measurements to the left and right of the normal decision instants, from which the user must calculate what the BER is at the normal decision instant. A microporcessor will be required to parse the data, detecting and removing non-gaussian regions and using the remaining data for BER extrapolation. Secondary Mode of Operation A secondary mode of operation is implemented. This mode is to give easy access to a coarse estimate of the eye quality. The circuitry is similar to that already described except that the measurement is performed autonomously by the ADN2817, and the result is output as a voltage on a pin, from which the actual BER can be inferred. As this mode does not perform scanning of the eye to separate out deterministic from random jitter effects the method can only predict the BER to within perhaps 2 decades, under normal applied jitter conditions. The user merely has to bring the Automode pin low, and read the voltage on the VBER pin, see Figure XX. Alternatively a 6 bit value can be read over the I2C. In secondary mode the dynamic range is limited.
Relative Bit Error Rate Monitor
The ADN2817 has a Bit Error Rate (BER) measurement feature that provides for an estimation of the actual bit error rate of the IC. The feature also allows data eye jitter profiling and Q-factor estimation. The implementation relies on the fact that by knowing the BER at sampling phases offset from the ideal sampling phase, it is possible to extrapolate to obtain an estimate of the BER at the actual sampling instant. This extrapolation relies on the assumption that the input jitter is composed of deterministic and random (gaussian) components. The implementation requires off-chip control and data processing to estimate the actual BER.
Brief Overview of Modes of Operation Two modes of operation are available for the BER feature. Only one mode can be operational at a time. The primary mode is to scan the input eye in the range of +/-0.5UI of the data centre, and read the measured pseudo-BER over the I2C. The user will then use the previously discussed algorithms to determine the BER. Using the BER feature in this way provides for the greatest accuracy in BER estimation as the magnitude of both Random (Gaussian) Jitter and Deterministic Jitter can be estimated, and used to predict the actual BER. In the secondary mode the part autonomously samples the PBER at 0.1UI offset, decodes this value to provide an estimate of the input BER. This estimate is output vis a DAC as an analogue voltage output. Primary Mode Power Saving There are three power modes in primary mode. In "BER Off " mode all the BER circuitry will be powered down, and operation of the DLL will be the same as the ADN2812. In "BER On" mode all of the BER logic and all the clock phase interpolators will be powered up. The user can perform a PBER measurement through the I2C. The clock signal from the VCO passes through the clock phase interpolator, to the NDC and DDC. In "BER Standby" mode the BER logic and the DDC clock phase interpolators are powered down. The dummy clock phase interpolator is powered up. The clock signal from the VCO passes through the clock phase interpolator to the NDC only. These modes are defined to allow optimal power saving opportunities. It is not possible to switch between BER Off
Rev. PrA | Page 24 of 35
Preliminary Technical Data
1.
ADN2817/ADN2818
The subharmonic must be a clock-type waveform i.e. transition density equal to 1 at the subharmonic frequency. The subharmonic must be continued to be applied until LOL goes LOW, i.e. until acquisition is completed. It doesn't matter how long the subharmonic remains after LOL goes LOW.
2.
Figure XX. VBER -vs- Bit Error Rate
Fi
In FDDI Mode, the output of the ADN2817 is squelched until the device has acquired lock of the subharmonic input. This causes all zeros to be transmitted out of the 2817 until lock has been achieved. Once locked, the outputs are enabled and begin transmitting data. For FDDI protocol, this would be when the 'H' symbols are being transmitted during link synchronization.
LOS Configuration
The LOS detector output, LOS Pin 22, can be configured to be either active high or active low. If CTRLC[2] is set to Logic 0 (default), the LOS pin is active high when a loss of signal condition is detected. Writing a 1 to CTRLC[2] configures the LOS pin to be active low when a loss of signal condition is detected.
Double Data Rate Mode
Setting I2C bit XXXX[X] = 1 puts the ADN2817/18 clock output through divide by two circuitry allowing direct interfacing to FPGAs that support data clocking on both rising and falling edges.
System Reset
A frequency acquisition can be initiated by writing a 1 followed by a 0 to the I2C Register Bit CTRLB[5]. This initiates a new frequency acquisition while keeping the ADN2817/ADN2818 in the operating mode that it was previously programmed to in registers CTRL[A], CTRL[B], and CTRL[C].
CLK HOLDOVER MODE
CLK Holdover Mode 2A:
FDDI Mode
A scheme has been implemented on the ADN2817/2818 that enables the device to lock to input data streams that appear as sub-harmonics of the desired datarate, e.g. FDDI during link synchronization. This works for any code where a subharmonic down to the 31st is transmitted. FDDI uses the 5th subharmonic. The implementation requires certain programming by the user and more importantly certain assumptions about the incoming data. The user is required to program the part into FDDI mode by setting bit FDDI_MODE[7]=1. The user then needs to program the target datarate, (for FDDI this is 125MHz). This is done by programming an upper and lower 9-bit code into I2C registers HI_CODE[8..0], LO_CODE[8..0], and CODE_LSB[1..0]. See Table XX for a look-up table showing the correct register settings for each datarate. The user must also program the subharmonic ratio into I2C register FDDI_MODE[6..2] that the ADN2817/18 needs to lock on to, e.g. FDDI_MODE[6..2] = 00101 for FDDI (5th subharmonic). The user has to de-program FDDI mode before the next datarate is applied. Here is what is required of the incoming data:
This mode of operation will be available in all LTD modes: The output clock frequency will remain within +/-5% if the input data is removed or changed. To operate in this mode, the user would write to the I2C to put the part into CLK Holdover Mode 2A mode by setting SEL_MODE[2]=1. The user must then initiate an acquisition via a software reset. The device will then lock onto the input datarate. At this point the output frequency remains within +/- 5% of the intial acquired value regardless of whether or not the input data is taken away or the datarate changes. Only a sw reset can initiate a new acquistion in this mode.
CLK Holdover Mode 2B:
This mode is selected by setting SEL_MODE[1]=1. In this mode, the output clock stays within +/-5% of the initial acquired frequency, even if the input data is taken away. Unlike CLK Holdover Mode 2A, in this mode the ADN2817/18 will initiate a new frequency acquisition automatically if the input datarate changes. This mode requires the inputs to be DC coupled because if the inputs are AC coupled and the input is taken away, any noise present on the inputs may be large enough to trigger a new frequency acquisition which would cause the clock output frequency to change.
CDR BYPASS MODE
The CDR on the ADN2817/18 can be bypassed by setting bit CTRLD[7]=1. In this mode the ADN2817/18 will feed the input directly through the input amplifiers to the output buffer,
Rev.Pr A | Page 25 of 35
ADN2817/ADN2818
completely bypassing the CDR.
Preliminary Technical Data
buffers for power savings. The clock output buffers can be disabled by setting CTRLD[5]=1. For additional power savings, e.g. in a low power standby mode, the data output buffers can also be disabled by setting CTRLD[6]=1.
DISABLE OUTPUT BUFFERS
The ADN2817/18 provides the option of disabling the output
Rev. PrA | Page 26 of 35
Preliminary Technical Data APPLICATIONS INFORMATION
PCB DESIGN GUIDELINES
Proper RF PCB design techniques must be used for optimal performance.
ADN2817/ADN2818
Power Supply Connections and Ground Planes
Use of one low impedance ground plane is recommended. The VEE pins should be soldered directly to the ground plane to reduce series inductance. If the ground plane is an internal plane and connections to the ground plane are made through vias, multiple vias can be used in parallel to reduce the series inductance, especially on Pin 23, which is the ground return for the output buffers. The exposed pad should be connected to the GND plane using plugged vias so that solder does not leak through the vias during reflow. Use of a 10 F electrolytic capacitor between VCC and VEE is recommended at the location where the 3.3 V supply enters the PCB. When using 0.1 F and 1 nF ceramic chip capacitors, they should be placed between the IC power supply VCC and VEE, as close as possible to the ADN2817/ADN2818 VCC pins.
If connections to the supply and ground are made through vias, the use of multiple vias in parallel helps to reduce series inductance, especially on Pin 24, which supplies power to the high speed CLKOUTP/CLKOUTN and DATAOUTP/ DATAOUTN output buffers. Refer to the schematic in Figure 24 for recommended connections. By using adjacent power supply and GND planes, excellent high frequency decoupling can be realized by using close spacing between the planes. This capacitance is given by
Cplane = 0.88 r A/d (pF ) where:
r is the dielectric constant of the PCB material. A is the area of the overlap of power and GND planes (cm2). d is the separation between planes (mm).
For FR-4, r = 4.4 mm and 0.25 mm spacing, C ~15 pF/cm2.
VCC 4 x 100 VCC + 10 0.1 1n 50 transmission lines DATAOU T P DATAOU T N CL KOUT P
VBER VCC VEE DATAOU T P DATAOU T N SQUEL CH CLK OU T P CLK OU T N
CL KOU T N
T H RAD J 9 REFCL K P 10 REFCL K N 11 VCC 12 VEE 13 CF2 14 CF1 15 LOL 16
AUT OM OD E VCC 0.1 1n VREF VCC NIN 0.1 PI N T IA 50 SL I CEP SL ICEN CI N VEE 50
1 2 3 4 5 6 7 8
Exposed Pad T ied Off To VEE Plane With Vias
24 23 22 21 20 19 18 17
VCC VEE L OS SDA SCK SAD D R5 VCC VEE
1n C I 2C Controller VCC 1n 0.1
VCC 0.1
32 31 30 29 28 27 26 25 NC
C
RT H
VCC 0.1 1n
0.47uF + 20% >300M insulation resistance
Figure 24. Typical ADN2817/ADN2818 Applications Circuit
Rev.Pr A | Page 27 of 35
ADN2817/ADN2818
Transmission Lines
Use of 50 transmission lines is required for all high frequency input and output signals to minimize reflections: PIN, NIN, CLKOUTP, CLKOUTN, DATAOUTP, DATAOUTN (also REFCLKP, REFCLKN, if a high frequency reference clock is used, such as 155 MHz). It is also necessary for the PIN/NIN input traces to be matched in length, and the CLKOUTP/N and DATAOUTP/N output traces to be matched in length to avoid skew between the differential traces. All high speed CML outputs, CLKOUTP/N and DATAOUTP/N, also require 100 back termination chip resistors connected between the output pin and VCC. These resistors should be placed as close as possible to the output pins. These 100 resistors are in parallel with on-chip 100 termination resistors to create a 50 back termination (see Figure 25). The high speed inputs, PIN and NIN, are internally terminated with 50 to an internal reference voltage (see Figure 26). A 0.1 F is recommended between VREF, Pin 3, and GND to provide an ac ground for the inputs. As with any high speed mixed-signal design, take care to keep all high speed digital traces away from sensitive analog nodes.
VCC 100 VCC VTERM 100 100 100 0.1 0.1 50 50 ADN2817/18 V TERM 50
Preliminary Technical Data
package has a central exposed pad. The pad on the printed circuit board should be at least as large as this exposed pad. The user must connect the exposed pad to VEE using plugged vias so that solder does not leak through the vias during reflow. This ensures a solid connection from the exposed pad to VEE.
Choosing AC Coupling Capacitors
AC coupling capacitors at the input (PIN, NIN) and output (DATAOUTP, DATAOUTN) of the ADN2817/ADN2818 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 27), causing pattern-dependent jitter (PDJ). The user must determine how much droop is tolerable 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. Example: Assuming that 2% droop can be tolerated, then the maximum differential droop is 4%. Normalizing to Vpp: Droop = V = 0.04 V = 0.5 Vpp (1 - e-t/) ; therefore, = 12t where: is the RC time constant (C is the ac coupling capacitor, R = 100 seen by C). t is the total discharge time, which is equal to n. n is the number of CIDs. T is the bit period.
Figure 25. Typical ADN2817/ADN2818 Applications Circuit
VCC ADN2817/18 CIN TIA 50 CIN PIN NIN 50 0.1uF
VREF
The capacitor value can then be calculated by combining the equations for and t: C = 12nT/R Once the capacitor value is selected, the PDJ can be approximated as
50 2.5V 3k
PDJ pspp = 0.5t r 1 - e ( -nT/RC ) / 0.6
(
)
where: PDJpspp is the amount of pattern-dependent jitter allowed; < 0.01 UI p-p typical.
Figure 26. ADN2817/ADN2818 AC-Coupled Input Configuration
Soldering Guidelines for Chip Scale Package
The lands on the 32 LFCSP are rectangular. The printed circuit board pad for these should be 0.1 mm longer than the package land length and 0.05 mm wider than the package land width. The land should be centered on the pad. This ensures that the solder joint size is maximized. The bottom of the chip scale
tr is the rise time, which is equal to 0.22/BW, where BW ~ 0.7 (bit rate). Note that this expression for tr is accurate only for the inputs. The output rise time for the ADN2817/ADN2818 is ~100 ps regardless of data rate.
Rev. PrA | Page 28 of 35
Preliminary Technical Data
ADN2817/ADN2818
VCC V1 CI N V1b V2b V2 AD N 2817 PIN 50
VREF
DATAOU T P L imamp CD R C OUT DATAOU T N
T IA
50 N IN
1
V1 V1b V2 V2b Vdiff
2
3
4
Vref VT H
Vdiff = V2-V2b VT H = AD N 2817 Quantizer T hreshold N OT ES: 1. D uring data patterns with high transition density, differential D C voltage at V1 and V2 is zero. 2. When the output of the T I A goes to CI D, V1 and V1b are driven to different D C levels. V2 and V2b discharge to the Vref level which effectively introduces a differential D C offset across the AC coupling capacitors. 3. When the burst of data starts again, the differential D C offset across the AC coupling capacitors is applied to the input levels causing a D C shift in the differential input. T his shift is large enough such that one of the states, either H I or L O depending on the levels of V1 and V1b when the T IA went to CID, is cancelled out. T he quantizer will not recognize this as a valid state. 4. T he D C offset slowly discharges until the differential input voltage exceeds the sensitivity of the AD N 2817. T he quantizer will be able to recognize both H I and L O states at this point.
Figure 27. Example of Baseline Wander
DC-COUPLED APPLICATION
The inputs to the ADN2817/ADN2818 can also be dc-coupled. This might be necessary in burst mode applications, where there are long periods of CIDs, and baseline wander cannot be tolerated. If the inputs to the ADN2817/ADN2818 are dccoupled, care must be taken not to violate the input range and common-mode level requirements of the ADN2817/ADN2818 (see Figure 28 through Figure 30). If dc coupling is required, and the output levels of the TIA do not adhere to the levels shown in Figure 29, then level shifting and/or an attenuator must be between the TIA outputs and the ADN2817/ADN2818 inputs.
VCC ADN2817 PIN TIA 50 NIN 50 0.1uF
VREF
50 2.5V 3k
Figure 28. DC-Coupled Application
Rev.Pr A | Page 29 of 35
ADN2817/ADN2818
PIN
Preliminary Technical Data
VPP = PIN - NIN = 2 x VSE = 2.0V MAX
VSE = 1.0V MAX
INPUT (V)
PIN
VPP = PIN - NIN = 2 x VSE = 10mV AT SENSITIVITY VSE = 5mV MIN VCM = 2.3V MIN (DC-COUPLED)
04228-0-027
INPUT (V)
VCM = 2.3V (DC-COUPLED)
NIN
NIN
Figure 29. Minimum Allowed DC-Coupled Input Levels
Figure 30. Maximum Allowed DC-Coupled Input Levels
Rev. PrA | Page 30 of 35
04228-0-028
Preliminary Technical Data COARSE DATA RATE READBACK LOOK-UP TABLE
Code is the 9-bit value read back from COARSE_RD[8:0].
Table 14. Look-Up Table
Code 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 FMID 5.1934e+06 5.1930e+06 5.2930e+06 5.3989e+06 5.5124e+06 5.6325e+06 5.7612e+06 5.8995e+06 6.0473e+06 6.2097e+06 6.3819e+06 6.5675e+06 6.7688e+06 6.9874e+06 7.2262e+06 7.4863e+06 7.4139e+06 7.4135e+06 7.5606e+06 7.7173e+06 7.8852e+06 8.0633e+06 8.2548e+06 8.4586e+06 8.6784e+06 8.9180e+06 9.1736e+06 9.4481e+06 9.7464e+06 1.0068e+07 1.0417e+07 1.0791e+07 1.0387e+07 1.0386e+07 1.0586e+07 1.0798e+07 1.1025e+07 1.1265e+07 1.1522e+07 1.1799e+07 1.2095e+07 1.2419e+07 1.2764e+07 1.3135e+07 1.3538e+07 1.3975e+07 1.4452e+07 1.4973e+07 Code 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 FMID 1.4828e+07 1.4827e+07 1.5121e+07 1.5435e+07 1.5770e+07 1.6127e+07 1.6510e+07 1.6917e+07 1.7357e+07 1.7836e+07 1.8347e+07 1.8896e+07 1.9493e+07 2.0136e+07 2.0833e+07 2.1582e+07 2.0774e+07 2.0772e+07 2.1172e+07 2.1596e+07 2.2049e+07 2.2530e+07 2.3045e+07 2.3598e+07 2.4189e+07 2.4839e+07 2.5527e+07 2.6270e+07 2.7075e+07 2.7950e+07 2.8905e+07 2.9945e+07 2.9655e+07 2.9654e+07 3.0242e+07 3.0869e+07 3.1541e+07 3.2253e+07 3.3019e+07 3.3834e+07 3.4714e+07 3.5672e+07 3.6694e+07 3.7792e+07 3.8985e+07 4.0273e+07 4.1666e+07 4.3164e+07 Code 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
Rev.Pr A | Page 31 of 35
ADN2817/ADN2818
FMID 4.1547e+07 4.1544e+07 4.2344e+07 4.3191e+07 4.4099e+07 4.5060e+07 4.6090e+07 4.7196e+07 4.8378e+07 4.9678e+07 5.1055e+07 5.2540e+07 5.4150e+07 5.5899e+07 5.7810e+07 5.9890e+07 5.9311e+07 5.9308e+07 6.0485e+07 6.1739e+07 6.3081e+07 6.4506e+07 6.6038e+07 6.7669e+07 6.9427e+07 7.1344e+07 7.3388e+07 7.5585e+07 7.7971e+07 8.0546e+07 8.3333e+07 8.6328e+07 8.3095e+07 8.3087e+07 8.4689e+07 8.6383e+07 8.8198e+07 9.0120e+07 9.2179e+07 9.4392e+07 9.6757e+07 9.9356e+07 1.0211e+08 1.0508e+08 1.0830e+08 1.1180e+08 1.1562e+08 1.1978e+08
Code 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
FMID 1.1862e+08 1.1862e+08 1.2097e+08 1.2348e+08 1.2616e+08 1.2901e+08 1.3208e+08 1.3534e+08 1.3885e+08 1.4269e+08 1.4678e+08 1.5117e+08 1.5594e+08 1.6109e+08 1.6667e+08 1.7266e+08 1.6619e+08 1.6617e+08 1.6938e+08 1.7277e+08 1.7640e+08 1.8024e+08 1.8436e+08 1.8878e+08 1.9351e+08 1.9871e+08 2.0422e+08 2.1016e+08 2.1660e+08 2.2360e+08 2.3124e+08 2.3956e+08 2.3724e+08 2.3723e+08 2.4194e+08 2.4695e+08 2.5233e+08 2.5802e+08 2.6415e+08 2.7067e+08 2.7771e+08 2.8538e+08 2.9355e+08 3.0234e+08 3.1188e+08 3.2218e+08 3.3333e+08 3.4531e+08
ADN2817/ADN2818
Code 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 FMID 3.3238e+08 3.3235e+08 3.3876e+08 3.4553e+08 3.5279e+08 3.6048e+08 3.6872e+08 3.7757e+08 3.8703e+08 3.9742e+08 4.0844e+08 4.2032e+08 4.3320e+08 4.4719e+08 4.6248e+08 4.7912e+08 4.7449e+08 4.7447e+08 4.8388e+08 4.9391e+08 5.0465e+08 5.1605e+08 5.2831e+08 5.4135e+08 Code 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 FMID 5.5542e+08 5.7075e+08 5.8711e+08 6.0468e+08 6.2377e+08 6.4437e+08 6.6666e+08 6.9062e+08 6.6476e+08 6.6470e+08 6.7751e+08 6.9106e+08 7.0558e+08 7.2096e+08 7.3743e+08 7.5514e+08 7.7405e+08 7.9485e+08 8.1688e+08 8.4064e+08 8.6640e+08 8.9438e+08 9.2496e+08 9.5825e+08 Code 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263
Preliminary Technical Data
FMID 9.4898e+08 9.4893e+08 9.6776e+08 9.8782e+08 1.0093e+09 1.0321e+09 1.0566e+09 1.0827e+09 1.1108e+09 1.1415e+09 1.1742e+09 1.2094e+09 1.2475e+09 1.2887e+09 1.3333e+09 1.3812e+09 1.3295e+09 1.3294e+09 1.3550e+09 1.3821e+09 1.4112e+09 1.4419e+09 1.4749e+09 1.5103e+09 Code 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 FMID 1.5481e+09 1.5897e+09 1.6338e+09 1.6813e+09 1.7328e+09 1.7888e+09 1.8499e+09 1.9165e+09 1.8980e+09 1.8979e+09 1.9355e+09 1.9756e+09 2.0186e+09 2.0642e+09 2.1132e+09 2.1654e+09 2.2217e+09 2.2830e+09 2.3484e+09 2.4187e+09 2.4951e+09 2.5775e+09 2.6666e+09 2.7625e+09
Rev. PrA | Page 32 of 35
Preliminary Technical Data OUTLINE DIMENSIONS
5.00 BSC SQ 0.60 MAX 0.60 MAX
25 24 32 1
ADN2817/ADN2818
PIN 1 INDICATOR
PIN 1 INDICATOR TOP VIEW 4.75 BSC SQ
0.50 BSC
BOTTOM VIEW
3.25 3.10 SQ 2.95
8
0.50 0.40 0.30 0.80 MAX 0.65 TYP 0.05 MAX 0.02 NOM 0.30 0.23 0.18 0.20 REF
17 16
9
0.25 MIN 3.50 REF
12 MAX
1.00 0.85 0.80 SEATING PLANE
COPLANARITY 0.08
COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-2
Figure 31. 32-Lead Frame Chip Scale Package [LFCSP] (CP-32) Dimensions shown in millimeters
ORDERING GUIDE
Model ADN2817/ADN2818ACP ADN2817/ADN2818ACP-RL ADN2817/ADN2818ACP-RL7 Temperature Range -40C to 85C -40C to 85C -40C to 85C Package Description 32-LFCSP 32-LFCSP, tape-reel, 2500 pcs 32-LFCSP, tape-reel, 1500 pcs Package Option CP-32 CP-32 CP-32
Rev.Pr A | Page 33 of 35
ADN2817/ADN2818 NOTES
Preliminary Technical Data
Rev. PrA | Page 34 of 35
Preliminary Technical Data NOTES
ADN2817/ADN2818
Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
(c) 2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. PR06001-0-3/06(PrA)
Rev.Pr A | Page 35 of 35

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