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10.7 Gbps, 3.3 V, Low Noise, TIA with Average Power Monitor ADN2820
FEATURES
Technology: high performance SiGe Bandwidth: 9 GHz Input noise current density: 1.0 A Optical sensitivity: -19.3 dBm Differential transimpedance: 5000 V/A Power dissipation: 200 mW Input current overload: 2.8 mA p-p Linear input range: 0.15 mA p-p Output resistance: 50 /side Output offset adjustment range: 240 mV Average input power monitor: 1 V/mA Die size: 0.87 mm x 1.06 mm
PRODUCT DESCRIPTION
The ADN2820 is a compact, high performance, 3.3 V power supply SiGe transimpedance amplifier (TIA) optimized for 10 Gbps Metro-Access and Ethernet systems. It is a single chip solution for detecting photodiode current with a differential output voltage. The ADN2820 features low input referred noise current and high output transimpedance gain, capable of driving a typical CDR or transceiver directly. A POWMON output is provided for input average power monitoring and alarm generation. Low nominal output offset enables dc output coupling to 3.3 V circuits. The OFFSET control input enables output slice level adjustment for asymmetric input signals. The ADN2820 operates with a 3.3 V power supply and is available in die form.
APPLICATIONS
10.7 Gbps optical modules SONET/SDH OC-192/STM-64 and 10 GbE receivers, transceivers, and transponders
FUNCTIONAL BLOCK DIAGRAM
3.3V RF 50 RF = 500 OUT (5) OUTB (6) h OFFSET (14) IN (13)' CB 0.85V CF POWMON (8) 20mA AV = 20dB 50 VCC (1,2,3)
GND (10, 11)
GND (4,7)
CLF (9)
CLF
03194-0-001
Figure 1. Functional Block Diagram/Typical Operating Circuit
Rev. 0
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2003 Analog Devices, Inc. All rights reserved.
ADN2820 TABLE OF CONTENTS
Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 ESD Caution.................................................................................. 4 Pad Layout and Functional Descriptions ...................................... 5 Pad Layout ..................................................................................... 5 Die Information............................................................................ 5 Pad Descriptions........................................................................... 5 Pad Coordinates ........................................................................... 5 Typical Performance Characteristics ............................................. 6 Applications........................................................................................8 Optical Sensitivity .........................................................................8 Optical Power Monitor.................................................................8 Output Offset Adjust Input ..........................................................9 Low Frequency Transimpedance Cutoff Capacitor Selection.9 Bandwidth versus Input Bond Wire Inductance.................... 10 Bandwidth versus Output Bond Wire Inductance................. 10 Butterfly Package Assembly ...................................................... 11 Outline Dimensions ....................................................................... 12 Ordering Guide .......................................................................... 12
REVISION HISTORY
Revision 0: Initial Version
Rev. 0 | Page 2 of 12
ADN2820 SPECIFICATIONS
Table 1. Electrical Specifications
Parameter DYNAMIC PERFORMANCE Bandwidth1, 2 Total Input RMS Noise1, 2 Small Signal Transimpedance Transimpedance Ripple Group Delay Variation
2 2
Conditions1 -3 dB DC to 10 GHz 100 MHz 100 MHz to 3 GHz 100 MHz to 3 GHz 100 MHz to 9 GHz IIN,P-P = 2.5 mA CLF = 0.1 F DC - 10 GHz, differential Peak-to-peak, <1 dB compression ER = 10 dB ER = 4 dB Differential, IIN P-P = 2.0 mA
Min 7.5 4000
Typ 9 1.0 5000 0.5 10 30 17 12 -10 0.15 2.8 1.9 1.1 200 0.85 VCC - 0.3 3 120 240 1 20
Max
Unit GHz A V/A dB ps ps ps kHz dB mA mA p-p mA p-p V p-p mW V V mV mV/V mV V/mA mV
6000
Total Peak-to-Peak Jitter 2, 3 Low Frequency Cutoff S22 Linear Input Range Input Overload Current1, 2 Maximum Output Swing DC PERFORMANCE Power Dissipation Input Voltage Output Common-Mode Voltage Output Offset Offset Adjust Sensitivity Offset Adjust Range POWMON Sensitivity POWMON Offset
1.4 1.0 0.88 147 0.75
264 0.93 +20
DC terminated to VCC IIN, AVE < 0.1 mA See Figure 3 See Figure 3 IIN, AVE = 10 A to 1 mA IIN, AVE = 0 A
-20
0.76
1.2
Min/Max VCC = 3.3 V 0.3 V, TAMBIENT = -15C to +85C; Typ VCC = 3.3 V, TAMBIENT = 25C. Photodiode capacitance CD = 0.22 pF 0.04 pF; photodiode resistance = 20 ; CB = CF = 100 pF; RF = 100 ; input wire bond inductance LIN = 0.5 nH 0.15 nH; output bond wire inductance LOUT, OUTB = 0.85 nH 0.15 nH; load impedance = 50 (each output, dc- or ac-coupled). 3 10-12 BER, 8 dB extinction ratio, 0.85 A/W PIN responsivity.
1 2
Rev. 0 | Page 3 of 12
ADN2820 ABSOLUTE MAXIMUM RATINGS
Table 2. ADN2820 Absolute Maximum Ratings
Parameter Supply Voltage (VCC to GND) Internal Power Dissipation Output Short Circuit Duration Maximum Input Current Storage Temperature Range Operating Ambient Temperature Range Maximum Junction Temperature Die Attach Temperature (<60 seconds) Rating 5.2 V Indefinite 5 mA -65C to +125C -15C to +85C 165C 450C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
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. 0 | Page 4 of 12
ADN2820 PAD LAYOUT AND FUNCTIONAL DESCRIPTIONS
PAD LAYOUT
1 VCC 14 OFFSET 2 VCC 3 VCC GND 4
DIE INFORMATION
Die Size
0.875 mm x 1.060 mm
Die Thickness
12 mils = 0.3 mm
Passivation Openings
13 IN 0,0' OUT 5
0.08 mm x 0.08 mm 0.12 mm x 0.08 mm
12
TEST
OUTB
6
0.08 mm x 0.12 mm
11 GND GND 10 CLF 9 GND POWMON 8
03194-0-002
7
Passivation Composition
5000 A Si3N4 (Top) +5000 A SiO2 (Bottom)
Pad Composition
Al/1% Cu
Figure 2. ADN2820 Pad Layout
Backside Contact
P-Type Handle (Oxide Isolated from Active Circuitry)
PAD DESCRIPTIONS
Table 3. Pad Descriptions
Pin No. 1-3 4, 7, 10, 11 5 6 8 9 12 13 14 Pad VCC GND OUT OUTB POWMON CLF TEST IN OFFSET Function Positive Supply. Bypass to GND with a 100 pF or greater single-layer capacitor. Ground. Positive Output. Drives 50 termination (ac or dc termination). Negative Output. Drives 50 termination (ac or dc termination). Input Average Power Monitor. Analog signal proportional to average optical input power. Leave open if unused. Low Frequency Cutoff Setpoint. Connect with a 0.1 F capacitor to GND for 20 kHz. Test Pad. Leave Floating. Current Input. Bond directly to reverse biased PIN or APD anode. Filter PIN or APD anode with 100 pF x 100 or greater. Output Offset Adjust Input. Leave open if not being used and the input slice threshold will automatically be set to the eye center.
PAD COORDINATES
Table 4. Pad Coordinates
Pin No. 1 2 3 4 5 6 7 PAD VCC VCC VCC GND OUT OUTB GND X (mm) -0.20 0.00 0.20 0.35 0.35 0.35 0.35 Y (mm) 0.45 0.45 0.45 0.30 0.10 -0.10 -0.30 Pin No. 8 9 10 11 12 13 14 PAD POWMON CLF GND GND TEST IN OFFSET X (mm) 0.20 0.00 -0.20 -0.35 -0.35 -0.35 -0.35 Y (mm) -0.45 -0.45 -0.45 -0.30 -0.10 0.10 0.30
Rev. 0 | Page 5 of 12
ADN2820 TYPICAL PERFORMANCE CHARACTERISTICS
0.25 0.20 0.15
VOUT DIFFERENTIAL (V)
-10 -15 -20
0.10
|s22| (dB)
0.05 0
-25 -30 -35 -40 -45
-0.05 -0.10 -0.15 -0.20
03194-0-008
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3.0
3.3
0.1 FREQUENCY (GHz)
1
OFFSET CONTROL INPUT (V)
Figure 3. VOUT Differential vs. OFFSET Adjust
Figure 6. Differential S22 vs. Frequency
10
1200
DIFFERENTIAL OUTPUT VOLTAGE (mV p-p)
1000
1
800
VPOWMON (V)
600
0.1
400
200
03194-0-009
1
10
100 IIN (A)
1k
10k
0
0.5
1.0
1.5
2.0
2.5
3.0
INPUT CURRENT (mA p-p)
Figure 4. VPOWMON vs. IIN
Figure 7. Output Voltage vs. Input Current
CH1
S21
LOG
5dB/REF 0dB
2:11.571dB
8.156 326 057GHz
80
CH1 MARKERS 1:14.563 dB 100.000 MHz
75
1
TZ GAIN (dB )
2
70
65
60
55
03194-0-010
START .050 000 000GHz
STOP 20.000 000 000GHz
0
0.5
1.0
1.5
2.0
2.5
3.0
INPUT CURRENT (mA p-p)
Figure 5. ADN2820 S21
Figure 8. Transimpedance Gain vs. Input Current
Rev. 0 | Page 6 of 12
03194-0-013
50
03194-0-012
0.001
0
03194-0-011
-0.25
-50 0.01
ADN2820
40 35 30 25 20 15 10 5
03194-0-014
TOTAL JITTER p-p (ps)
0 0 0.5 1.0 1.5 2.0 2.5 3.0 AVERAGE CURRENT (mA)
Figure 9. Total Jitter Peak-to-Peak vs. Average Input Current (IIN = 2 mA p-p)
Figure 11. Electrical Eye Diagram at 10 Gbps, PRBS 2 31 with IIN = 100 A p-p
60
50
TOTAL JITTER p-p (ps)
40
30
20
10
0
0.5
1.0
1.5
2.0
2.5
3.0
INPUT AMPLITUDE p-p (mA)
03194-0-015
Figure 10. Total Jitter Peak-to-Peak vs. Input Amplitude (ER = 10 dB)
Figure 12. Electrical Eye Diagram at 10 Gbps, PRBS 2 31 with IIN = 2.5 mA p-p
Rev. 0 | Page 7 of 12
03194-0-017
0
03194-0-016
ADN2820 APPLICATIONS
OPTICAL SENSITIVITY
Sensitivity(dBm) = 10 log 10 (IRMS x + VS / ZT ) x (ER + 1) x (1000mW /W ) 2( ER - 1)
From a POWMON measurement, the average input power can be estimated by calculating the optical power monitor (OPM): OPM (W) = (POWMON (V) - POWMONOFFSET (V))/( (A/W) x POWMONGAIN (V/A)) OPM calculation from typical ADN2820 POWMON versus IIN,AVE measurement data: (POWMONOFFSET = 20 mV, POWMONGAIN = 1 V/mA, =1 A/W)
0
where: = photodiode responsivity (A/W), 0.85 A/W typical IRMS = TIA input referred noise (A), typically 1.05 A for the ADN2820 = BER factor, = 14.1 for 10-12 BER ER = extinction ratio, 8 dB typical VS = PA/CDR input sensitivity (V), 5 mV to 100 mV ZT = TIA transimpedance (V/A), 5 k for ADN2820 Table 5. Optical Sensitivity
Optical Input Sensitivity (dBm) PA/CDR 100 mV Input 50 mV Sensitivity (VS) 25 mV 10 mV 5 mV Transimpedance (ZT) 2 k 5 k Infinite -13.1 -15.7 -19.3 -15.1 -17.1 -19.3 -16.7 -18.1 -19.3 -18.1 -18.8 -19.3 -18.7 -19.0 -19.3
-5
-10
OPM (dBm)
-15
-20
-25
OPTICAL POWER MONITOR
Average optical power monitor (OPM) measurement is a recommended diagnostic feature in module multisource specification agreements (MSAs) such as the 300-pin 10 Gb transponder (MSA300) and 10 Gb form factor pluggable module (XFP) specifications.
OPM MEASUREMENT ERROR (dB)
-25
-20
-15
-10
-5
0
AVERAGE INPUT POWER (dBm)
Figure 13. POWMON Transfer Function
1.0
The ADN2820 enables the simple calculation of OPM using the POWMON output, which is linearly proportional to the average input current. When monitoring the POWMON output, connect to a high impedance input; typical POWMON output impedance is 1 k. To disable the POWMON feature, leave the pad floating (not bonded). Assuming linear diode responsivity , average input current is linearly proportional to average input power: IIN,AVE (A) = (A/W) x PIN,AVE (W) Ideally, POWMON (V) = (A/W) x PIN,AVE (W) x POWMONGAIN (V/A) + POWMONOFFSET (V)
0.6
0.2
-0.2
-0.6
-25
-20
-15
-10
-5
0
AVERAGE INPUT POWER (dBm)
Figure 14. POWMON Accuracy
Rev. 0 | Page 8 of 12
03194-0-002
-1.0 -30
03194-0-001
-30 -30
ADN2820
OUTPUT OFFSET ADJUST INPUT
Long reach optical links may suffer from unbalanced 1 and 0 signal shaping due to dispersion and/or optical or avalanche amplification noise. The ADN2820 enables the user to adjust the input-referred slice level by adjusting the output offset with the ADN2820's outputs dc-coupled. With the OFFSET pad open (not bonded), the average output voltage offset [OUT - OUTB] is internally balanced to be less than 5 mV. When externally driven by a voltage source, the ADN2820 average output voltage offset [OUT - OUTB] is linearly proportional to an applied OFFSET input voltage:
Applied Offset (V) = (OFFSET (V) - ~1.6 V) x OFFSETGAIN (mV/V)
LOW FREQUENCY TRANSIMPEDANCE CUTOFF CAPACITOR SELECTION
Digital encoding methods may generate long strings of 1s or 0s, requiring the transimpedance amplifier pass band to extend to 1 MHz or below. To accommodate this requirement, the ADN2820 has -3 dB low frequency transimpedance cutoff set by external capacitor CLF. For CLF, values greater than 1000 pF, the typical -3 dB low frequency transimpedance cutoff can be estimated by the equation f-3dB ~ 2 kHz x (1 F/CLF) Because CLF is not part of the 10 Gbps signal chain, it is not required to be a high frequency capacitor type. A ceramic capacitor is recommended.
100M
TZ -3dB LOW FREQUENCY CUTOFF (Hz)
where: OFFSET = voltage applied to the OFFSET pad OFFSETGAIN = 120 mV/V With transimpedance, TZ, the input referred slice adjust can be calculated from the following equation:
Input Slice Adjust = 1/TZ x (OFFSET (V) - ~1.6 V) x OFFSETGAIN (mV/V))
50
INPUT REFERRED SLICE ADJUST (A)
10M
1M
100k
40 30 20 10 0 -10 -20 -30 -40
03194-0-003
10k
10pF
0.1nF
1nF
10nF
0.1F
1F
EXTERNAL CLF CAPACITANCE VALUE
Figure 16. Low Frequency Transimpedance Cutoff vs. CLF Capacitance Using Typical Data with a 0.1 F Ceramic Capacitor and Simulation Results with 1 pF to 1 F Capacitance
-50 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 OFFSET CONTROL INPUT (V)
Figure 15. Input Slice Adjust vs. OFFSET Calculation Using Typical [OUT,OUTB] vs. OFFSET Measurement Data
Rev. 0 | Page 9 of 12
03194-0-004
1k 1pF
ADN2820
BANDWIDTH VERSUS INPUT BOND WIRE INDUCTANCE
The ADN2820's -3 dB bandwidth (BW) is a strong function of input (IN) bond wire inductance (LIN). The maximum BW peaks near and falls rapidly after the resonant frequency of the input bond wire inductance and photodiode capacitance (CD) ~ 1/(2 x (LIN x CD)).
BANDWIDTH VERSUS OUTPUT BOND WIRE INDUCTANCE
The ADN2820 -3 dB bandwidth (BW) depends strongly on the output (OUT, OUTB) inductance values (LOUT, LOUTB). With output inductance greater than 2 nH, the BW is dominated by the output LOUT, LOUTB/(RO + RL) settling time constant, where RO = RL = 50 are the nominal single-ended output resistance and load impedance. Table 7. Simulated ADN2820 -3 dB BW vs LOUT, LOUTB
LOUT, LOUTB (nH) 0 1 2 3
76
Table 6. Simulated ADN2820 -3 dB BW vs. LIN
LIN (nH) 0 1 2 3
76 75 74
-3 dB Bandwidth (GHz) 7.4 9.0 7.8 7.0
3nH
-3 dB Bandwidth (GHz) 9.1 9.0 7.5 5.9
2nH
75 1nH 74
1nH
0nH
SIMULATED DIFFERENTIAL TRANSIMPEDANCE (dB )
73 0nH 72 71 70 69 68 67
03194-0-005
SIMULATED DIFFERENTIAL TRANSIMPEDANCE (dB )
73 72 71 70 69 68 67
03194-0-006
3nH
2nH
66 0.1
1
10 FREQUENCY (GHz)
100
66 0.1
1
10 FREQUENCY (GHz)
100
Figure 17. Simulated Differential Transimpedance (dB) vs. Frequency (Hz) with 0 nH, 1 nH, 2 nH, and 3 nH LIN Inductance
Figure 18. Simulated Differential Transimpedance (dB) vs. Frequency (Hz) with 0 nH, 1 nH, 2 nH, and 3 nH LOUT, LOUTB inductance
Note: LOUT, LOUTB = 1 nH, CD = 0.22 pF. Recommendation: LIN x CD = 1 nH x 0.22 pF.
Note: LIN = 1 nH, CD = 0.22 pF. Recommendation: LOUT, LOUTB 1 nH
Rev. 0 | Page 10 of 12
ADN2820
BUTTERFLY PACKAGE ASSEMBLY
OFFSET VCC
7.5mm Rf Cb Cf PD Clf 0mm
03194-0-007
5mm OUT OUTB 2.5mm
POWMON
Figure 19. Butterfly Package
Table 8. Bill of Materials
PD TIA CB CLF CF RF Qty. 1 1 2 1 1 1 Description VENDOR SPECIFIC (0.5 mm x 0.5 mm) ADN2820 (0.87 mm x 1.06 mm) GM250X7R10216 (0.5 mm x 0.5 mm) GM260Y5V104Z10 (0.8 mm x 0.8 mm) D20BV201J5PX (0.5 mm x 0.5 mm) WMIF0021000AJ (0.4 mm x 0.5 mm) Source 10 Gbps Photodiode Analog Devices SiGe 10 Gbps Transimpedance Amplifier Murata 1000 pF Ceramic Single Layer Capacitor Murata 0.1 F Ceramic Single Layer Capacitor DiLabs 100 pF RF Single Layer Capacitor Vishay 100 Thin Film Microwave Resistor
Rev. 0 | Page 11 of 12
ADN2820 OUTLINE DIMENSIONS
1 2 3 14 4
13
ADN2820
SINGLE PAD SIZE: 0.080 mm x 0.080 mm (pads 1, 2, 3, 5, 6, 8, 9, 12, 13, 14)
5
1.060 mm
12
DOUBLE PAD SIZE: 0.120 mm x 0.080 mm (pads 4, 7, 10, 11)
6
11
7
10
9
0.875 mm
8
0.30 mm
Figure 20. 14-Pad Bare Die Dimensions shown in millimeters
ORDERING GUIDE
Model ADN2820ACHIPS Temperature Range -25C to +85C Package Description Die Form
(c) 2003 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C03194-0-10/03(0)
Rev. 0 | Page 12 of 12

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