10.7 Gbps, 3.3 V, Low Noise,
TIA with Average Power Monitor
ADN2820
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 © 2003 Analog Devices, Inc. All rights reserved.
FEATURES
Technology: high performance SiGe
Bandwidth: 9 GHz
Input noise current density: 1.0 µA
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 Ω/side
Output offset adjustment range: 240 mV
Average input power monitor: 1 V/mA
Die size: 0.87 mm × 1.06 mm
APPLICATIONS
10.7 Gbps optical modules
SONET/SDH OC-192/STM-64 and 10 GbE
receivers, transceivers, and transponders
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.
FUNCTIONAL BLOCK DIAGRAM
R
F
3.3V
C
F
C
B
R
F
= 500Ω
VCC (1,2,3)
IN (13)'
GND (10, 11) GND (4,7)
0.85V 20mA
A
V
= 20dB
50Ω50Ω
CLF
CLF (9)
POWMON (8)
OUT (5)
OUTB (6)
OFFSET (14)
hυ
03194-0-001
Figure 1. Functional Block Diagram/Typical Operating Circuit
ADN2820
Rev. 0 | Page 2 of 12
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
ADN2820
Rev. 0 | Page 3 of 12
SPECIFICATIONS
Table 1. Electrical Specifications
Parameter Conditions1Min Typ Max Unit
DYNAMIC PERFORMANCE
Bandwidth1, 2–3 dB 7.5 9 GHz
Total Input RMS Noise1, 2 DC to 10 GHz 1.0 µA
Small Signal Transimpedance 100 MHz 4000 5000 6000 V/A
Transimpedance Ripple2 100 MHz to 3 GHz ±0.5 dB
Group Delay Variation2 100 MHz to 3 GHz ±10 ps
100 MHz to 9 GHz ±30 ps
Total Peak-to-Peak Jitter 2, 3IIN,P-P = 2.5 mA 17 ps
Low Frequency Cutoff CLF = 0.1 µF 12 kHz
S22 DC – 10 GHz, differential –10 dB
Linear Input Range Peak-to-peak, <1 dB compression 0.15 mA
Input Overload Current1, 2 ER = 10 dB 1.4 2.8 mA p-p
ER = 4 dB 1.0 1.9 mA p-p
Maximum Output Swing Differential, IIN P-P = 2.0 mA 0.88 1.1 V p-p
DC PERFORMANCE
Power Dissipation 147 200 264 mW
Input Voltage 0.75 0.85 0.93 V
Output Common-Mode Voltage DC terminated to VCC VCC – 0.3 V
Output Offset IIN, AVE < 0.1 mA –20 ±3 +20 mV
Offset Adjust Sensitivity See Figure 3 120 mV/V
Offset Adjust Range See Figure 3 240 mV
POWMON Sensitivity IIN, AVE = 10 µA to 1 mA 0.76 1 1.2 V/mA
POWMON Offset IIN, AVE = 0 µA 20 mV
1 Min/Max VCC = 3.3 V ± 0.3 V, TAMBIENT = –15°C to +85°C; Typ VCC = 3.3 V, TAMBIENT = 25°C.
2 Photodiode capacitance CD = 0.22 pF ± 0.04 pF; photodiode resistance = 20 Ω; CB = CF = 100 pF; RF = 100 Ω; 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 Ω (each output, dc- or ac-coupled).
3 10–12 BER, 8 dB extinction ratio, 0.85 A/W PIN responsivity.
ADN2820
Rev. 0 | Page 4 of 12
ABSOLUTE MAXIMUM RATINGS
Table 2. ADN2820 Absolute Maximum Ratings
Parameter Rating
Supply Voltage (VCC to GND) 5.2 V
Internal Power Dissipation
Output Short Circuit Duration Indefinite
Maximum Input Current 5 mA
Storage Temperature Range –65°C to +125°C
Operating Ambient Temperature Range –15°C to +85°C
Maximum Junction Temperature 165°C
Die Attach Temperature (<60 seconds) 450°C
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.
ADN2820
Rev. 0 | Page 5 of 12
PAD LAYOUT AND FUNCTIONAL DESCRIPTIONS
PAD LAYOUT DIE INFORMATION
123
4
5
6
7
8
9
10
11
12
13
14
VCC VCC VCC
GND
GND
GND
GND
OUT
OUTB
TEST
IN
OFFSET
CLF POWMON
0,0'
03194-0-002
Figure 2. ADN2820 Pad Layout
Die Size
0.875 mm × 1.060 mm
Die Thickness
12 mils = 0.3 mm
Passivation Openings
0.08 mm × 0.08 mm
0.12 mm × 0.08 mm
0.08 mm × 0.12 mm
Passivation Composition
5000 Å Si3N4 (Top)
+5000 Å SiO2 (Bottom)
Pad Composition
Al/1% Cu
Backside Contact
P-Type Handle (Oxide Isolated from Active Circuitry)
PAD DESCRIPTIONS
Table 3. Pad Descriptions
Pin No. Pad Function
1–3 VCC Positive Supply. Bypass to GND with a 100 pF or greater single-layer capacitor.
4, 7, 10, 11 GND Ground.
5 OUT Positive Output. Drives 50 Ω termination (ac or dc termination).
6 OUTB Negative Output. Drives 50 Ω termination (ac or dc termination).
8 POWMON
Input Average Power Monitor. Analog signal proportional to average optical input power. Leave open if
unused.
9 CLF Low Frequency Cutoff Setpoint. Connect with a 0.1 μF capacitor to GND for 20 kHz.
12 TEST Test Pad. Leave Floating.
13 IN Current Input. Bond directly to reverse biased PIN or APD anode. Filter PIN or APD anode with 100 pF × 100 Ω
or greater.
14 OFFSET
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. PAD X (mm) Y (mm)
1 VCC –0.20 0.45
2 VCC 0.00 0.45
3 VCC 0.20 0.45
4 GND 0.35 0.30
5 OUT 0.35 0.10
6 OUTB 0.35 –0.10
7 GND 0.35 –0.30
Pin
No. PAD X (mm) Y (mm)
8 POWMON 0.20 –0.45
9 CLF 0.00 –0.45
10 GND –0.20 –0.45
11 GND –0.35 –0.30
12 TEST –0.35 –0.10
13 IN –0.35 0.10
14 OFFSET –0.35 0.30
ADN2820
Rev. 0 | Page 6 of 12
TYPICAL PERFORMANCE CHARACTERISTICS
–0.25
–0.20
–0.15
–0.10
–0.05
0
0.05
0.10
0.15
0.20
0.25
V
OUT
DIFFERENTIAL (V)
OFFSET CONTROL INPUT (V)
0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.3
03194-0-008
Figure 3. VOUT Differential vs. OFFSET Adjust
V
POWMON
(V)
0.001
1
0.1
10
I
IN
(µA)
101 100 1k 10k
03194-0-009
Figure 4. VPOWMON vs. IIN
START .050 000 000GHz STOP 20.000 000 000GHz
CH1 S21 LOG 5dB/REF 0dB 2:11.571dB 8.156 326 057GHz
03194-0-010
CH1 MARKERS
1:14.563 dB
100.000 MHz
12
Figure 5. ADN2820 S21
–50
–45
–40
–35
–30
–25
|s22| (dB)
–20
–15
–10
FREQUENCY (GHz)
0.01 0.1 1
03194-0-011
Figure 6. Differential S22 vs. Frequency
0
200
400
600
800
1000
1200
DIFFERENTIAL OUTPUT VOLTAGE (mV p-p)
1.0 1.50 0.5 2.0 2.5 3.0
INPUT CURRENT (mA p-p)
03194-0-012
Figure 7. Output Voltage vs. Input Current
50
55
60
65
70
75
80
T
Z
GAIN (dB Ω)
1.0 1.50 0.5 2.0 2.5 3.0
INPUT CURRENT (mA p-p)
03194-0-013
Figure 8. Transimpedance Gain vs. Input Current
ADN2820
Rev. 0 | Page 7 of 12
0
5
10
15
20
25
30
35
40
TOTAL JITTER p-p (ps)
1.0 1.50 0.5 2.0 2.5 3.0
AVERAGE CURRENT (mA)
03194-0-014
Figure 9. Total Jitter Peak-to-Peak vs. Average Input Current (IIN = 2 mA p-p)
0
10
20
30
40
50
60
TOTAL JITTER p-p (ps)
1.0 1.50 0.5 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)
03194-0-016
Figure 11. Electrical Eye Diagram at 10 Gbps, PRBS 2 31 with IIN = 100 µA p-p
03194-0-017
Figure 12. Electrical Eye Diagram at 10 Gbps, PRBS 2 31 with IIN = 2.5 mA p-p
ADN2820
Rev. 0 | Page 8 of 12
APPLICATIONS
OPTICAL SENSITIVITY
)1(2
)/1000()1()/(
log10)( 10 −ρ
×+×+α×
=ER
WmWERZVI
dBmySensitivit TSRMS
where:
ρ = photodiode responsivity (A/W), 0.85 A/W typical
IRMS = TIA input referred noise (A), typically 1.05 µA for the
ADN2820
α = BER factor, α = 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 kΩ for ADN2820
Table 5. Optical Sensitivity
Transimpedance (ZT)
Optical Input Sensitivity (dBm) 2 kΩ 5 kΩ Infinite
100 mV –13.1 –15.7 –19.3
50 mV –15.1 –17.1 –19.3
25 mV –16.7 –18.1 –19.3
10 mV –18.1 –18.8 –19.3
PA/CDR
Input
Sensitivity (VS)
5 mV –18.7 –19.0 –19.3
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.
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 kΩ. To disable the POWMON feature, leave the
pad floating (not bonded).
Assuming linear diode responsivity ρ, average input current is
linearly proportional to average input power:
IIN,AVE (A) = ρ (A/W) × PIN,AVE (W)
Ideally,
POWMON (V) = ρ (A/W) × PIN,AVE (W) ×
POWMONGAIN (V/A) + POWMONOFFSET (V)
From a POWMON measurement, the average input power can
be estimated by calculating the optical power monitor (OPM):
OPM (W) = (POWMON (V) – POWMONOFFSET (V))/(ρ (A/W)
× POWMONGAIN (V/A))
OPM calculation from typical ADN2820 POWMON versus
IIN,AVE measurement data:
(POWMONOFFSET = 20 mV, POWMONGAIN = 1 V/mA, ρ =1 A/W)
–30
–25
–20
–15
–10
–5
0
OPM (dBm)
–20 –15–30 –25 –10 –5 0
AVERAGE INPUT POWER (dBm)
03194-0-001
Figure 13. POWMON Transfer Function
–1.0
–0.6
–0.2
0.2
0.6
1.0
OPM MEASUREMENT ERROR (dB)
–20 –15–30 –25 –10 –5 0
AVERAGE INPUT POWER (dBm)
03194-0-002
Figure 14. POWMON Accuracy
ADN2820
Rev. 0 | Page 9 of 12
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) × OFFSETGAIN (mV/V)
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 × (OFFSET (V) – ~1.6 V) × OFFSETGAIN (mV/V))
–50
–40
–30
–20
–10
0
10
20
30
40
50
INPUT REFERRED SLICE ADJUST (µA)
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)
03194-0-003
Figure 15. Input Slice Adjust vs. OFFSET Calculation Using Typical
[OUT,OUTB] vs. OFFSET Measurement Data
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 × (1 µF/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.
1k
10k
100k
1M
10M
100M
T
Z
–3dB LOW FREQUENCY CUTOFF (Hz)
0.1nF 1nF1pF 10pF 10nF 0.1
µ
F1
µ
F
EXTERNAL C
LF
CAPACITANCE VALUE
03194-0-004
Figure 16. Low Frequency Transimpedance Cutoff vs. CLF Capacitance Using
Typical Data with a 0.1 µF Ceramic Capacitor and Simulation Results with
1 pF to 1 µF Capacitance
ADN2820
Rev. 0 | Page 10 of 12
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/(2π × √(LIN × CD)).
Table 6. Simulated ADN2820 –3 dB BW vs. LIN
LIN (nH) –3 dB Bandwidth (GHz)
0 7.4
1 9.0
2 7.8
3 7.0
66
67
68
69
70
71
72
73
74
75
76
SIMULATED DIFFERENTIAL
TRANSIMPEDANCE (dB Ω)
FREQUENCY (GHz)
10.1 10 100
03194-0-005
0nH
1nH
2nH
3nH
Figure 17. Simulated Differential Transimpedance (dB) vs. Frequency (Hz)
with 0 nH, 1 nH, 2 nH, and 3 nH LIN Inductance
Note: LOUT, LOUTB = 1 nH, CD = 0.22 pF.
Recommendation: LIN × CD = 1 nH × 0.22 pF.
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 Ω are the nominal single-ended output resistance
and load impedance.
Table 7. Simulated ADN2820 –3 dB BW vs LOUT, LOUTB
LOUT, LOUTB (nH) –3 dB Bandwidth (GHz)
0 9.1
1 9.0
2 7.5
3 5.9
66
67
68
69
70
71
72
73
74
75
76
SIMULATED DIFFERENTIAL
TRANSIMPEDANCE (dB Ω)
FREQUENCY (GHz)
10.1 10 100
03194-0-006
3nH
0nH
1nH
2nH
Figure 18. Simulated Differential Transimpedance (dB) vs. Frequency (Hz)
with 0 nH, 1 nH, 2 nH, and 3 nH LOUT, LOUTB inductance
Note: LIN = 1 nH, CD = 0.22 pF.
Recommendation: LOUT, LOUTB ≤ 1 nH
ADN2820
Rev. 0 | Page 11 of 12
BUTTERFLY PACKAGE ASSEMBLY
03194-0-007
Cb
PD
V
CC
OFFSET
POWMON
OUT
OUTB
7.5mm
5mm
2.5mm
0mm
C
lf
Rf
Cf
Figure 19. Butterfly Package
Table 8. Bill of Materials
Qty. Description Source
PD 1 VENDOR SPECIFIC (0.5 mm × 0.5 mm) 10 Gbps Photodiode
TIA 1 ADN2820 (0.87 mm × 1.06 mm) Analog Devices SiGe 10 Gbps Transimpedance Amplifier
CB2 GM250X7R10216 (0.5 mm × 0.5 mm) Murata 1000 pF Ceramic Single Layer Capacitor
CLF 1 GM260Y5V104Z10 (0.8 mm × 0.8 mm) Murata 0.1 µF Ceramic Single Layer Capacitor
CF1 D20BV201J5PX (0.5 mm × 0.5 mm) DiLabs 100 pF RF Single Layer Capacitor
RF 1 WMIF0021000AJ (0.4 mm × 0.5 mm) Vishay 100 Ω Thin Film Microwave Resistor
ADN2820
Rev. 0 | Page 12 of 12
OUTLINE DIMENSIONS
0.875 mm
1.060 mm
123
4
5
6
7
8
9
10
11
12
13
14
SINGLE PAD SIZE: 0.080 mm x 0.080 mm
(pads 1, 2, 3, 5, 6, 8, 9, 12, 13, 14)
DOUBLE PAD SIZE: 0.120 mm x 0.080 mm
(pads 4, 7, 10, 11)
ADN2820
0.30 mm
Figure 20. 14-Pad Bare Die
Dimensions shown in millimeters
ORDERING GUIDE
Model Temperature Range Package Description
ADN2820ACHIPS –25°C to +85°C Die Form
© 2003 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
C03194–0–10/03(0)
