3.3 V, 3.2 Gbps,
Limiting Amplifier
ADN2891
FEATURES
Input sensitivity: 4 mV p-p
80 ps rise/fall times
CML outputs: 700 mV p-p differential
Programmable LOS detector: 3.5 mV to 35 mV
Rx signal strength indicator (RSSI)
SFF-8472-compliant average power measurement
Single-supply operation: 3.3 V
Low power dissipation: 145 mW
Available in space-saving 3 mm × 3 mm, 16-lead LFCSP
Extended temperature range: −40°C to +95°C
SFP reference design available
GENERAL DESCRIPTION
The ADN2891 is a 3.2 Gbps limiting amplifier with integrated
loss-of-signal (LOS) detection circuitry and a received signal
strength indicator (RSSI). This part is optimized for SONET,
Gigabit Ethernet (GbE), and Fibre Channel optoelectronic
conversion applications. The ADN2891 has a differential input
sensitivity of 4 mV p-p and accepts up to a 2.0 V p-p differential
input overload voltage. The ADN2891 supports current mode
logic (CML) outputs with controlled rise and fall times.
By monitoring the bias current through a photodiode, the on-
chip RSSI detector measures the average power received with
2% typical linearity over the entire valid input range of the
photodiode. The on-chip RSSI detector facilitates SFF-8472-
compliant optical transceivers by eliminating the need for
external RSSI detector circuitry.
Additional features include a programmable loss-of-signal
(LOS) detector and output squelch.
The ADN2891 is available in a 3 mm × 3 mm, 16-lead LFCSP.
APPLICATIONS
SFP/SFF/GBIC optical transceivers
OC-3/OC-12/OC-48, GbE, Fibre Channel (FC) receivers
10GBASE-LX4 transceivers
WDM transponders
FUNCTIONAL BLOCK DIAGRAM
AVCC
AVEE
DRVCC
DRVCC
DRVEE
ADN2891
50Ω
PIN
50Ω
OUTP
OUTN
50Ω
50Ω
3kΩ
PD_VCC
PD_CATHODE
05244-001
ADN2880
NIN
+V
V
REF
LOS
RSSI/LOS
DETECTOR
10k
Ω
RSSI_OUT
ADuC7020
CAZ1
0.01
μ
F
CAZ2
THRADJ SQUELCH
Figure 1.
Rev. A
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: 781.461.3113
©2005 Analog Devices, Inc. All rights reserved.
ADN2891
TABLE OF CONTENTS
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
Thermal Resistance ...................................................................... 5
ESD Caution.................................................................................. 5
Pin Configuration and Function Descriptions............................. 6
Typical Performance Characteristics ............................................. 7
Theory of Operation ...................................................................... 10
Limiting Amplifier ..................................................................... 10
Loss of Signal (LOS) Detector .................................................. 10
Received Signal Strength Indicator (RSSI) ............................. 10
Squelch Mode ............................................................................. 10
Applications..................................................................................... 11
PCB Design Guidelines ............................................................. 11
Outline Dimensions ....................................................................... 13
Ordering Guide .......................................................................... 13
REVISION HISTORY
7/05—Rev. 0 to Rev. A
Changes to Table 1............................................................................ 3
Changes to Ordering Guide .......................................................... 13
3/05—Revision 0: Initial Version
Rev. A | Page 2 of 16
ADN2891
SPECIFICATIONS
Test Conditions: VCC = 2.9 V to 3.6 V, VEE = 0 V, T
A
= −40°C to +95°C, unless otherwise noted.
Table 1.
Parameter
QUANTIZER DC CHARACTERISTICS
Input Voltage Range
Input Common Mode
Differential Input Range
Differential Input Sensitivity
Input Offset Voltage
Input RMS Noise
Input Resistance
Input Capacitance
QUANTIZER AC CHARACTERISTICS
Input Data Rate
Small Signal Gain
S11
S22
Random Jitter
Deterministic Jitter
Low Frequency Cutoff
Power Supply Rejection Ratio
LOSS OF SIGNAL DETECTOR (LOS)
LOS Assert Level
Electrical Hysteresis
LOS Assert Time
LOS De-Assert Time
RSSI
Input Current Range
RSSI Output Linearity
Gain
Offset
Compliance Voltage
POWER SUPPLIES
VCC
I
CC
OPERATING TEMPERATURE RANGE
CML OUTPUT CHARACTERISTICS
Output Impedance
Output Voltage Swing
Output Rise and Fall Time
Min
1.8
2.1
5.2
3.5
100
235
50
0.65
3200
50
−10
−10
4.0
9.0
30
1.0
45
Typ
Max
2.8
2.7
2.0
Unit
V p-p
V
V p-p
mV p-p
μV
μV rms
Ω
pF
Mb/s
dB
dB
dB
ps rms
ps p-p
kHz
kHz
dB
Test Conditions/Comments
At PIN or NIN, dc-coupled
DC-coupled
AC-coupled
3.2 Gbps, PRBS 2
23
− 1, BER ≤ 10
−10
Single-ended
155
6.4
34
Differential
Differential, f < 3.2 GHz
Differential, f < 3.2 GHz
Input ≥ 10 mV p-p, OC-48, PRBS 2
23
− 1
Input ≥ 10 mV p-p, OC-48, PRBS 2
23
− 1
CAZ = Open
CAZ = 0.0 1 μF
f < 10 MHz
1.9
19
2.4
2.75
3.5
35
5.0
5.0
950
62
5.6
53
mV p-p
mV p-p
dB
dB
ns
ns
μA
%
mA/mA
nA
V
R
THRADJ
= 100 kΩ
R
THRADJ
= 1 kΩ
OC-3, PRBS 2
23
− 1
OC-48, PRBS 2
23
− 1
DC-coupled
DC-coupled
5
2
1.0
145
VCC − 0.9
1000
VCC − 0.4
5 μA < I
IN
≤ 1000 μA
I
RSSI
/I
PD
Difference between measured RSSI output
and PD_CATHODE (input) current of 5 μA
Measured at PD_CATHODE, with I = 5 μA
or I = 1 mA
2.9
−40
3.3
45
+25
50
660
80
3.6
49
+95
V
mA
°C
Ω
mV p-p
ps
T
MIN
to T
MAX
Single-ended
Differential
20% to 80%
600
850
130
Rev. A | Page 3 of 16
ADN2891
Parameter
LOGIC INPUTS (SQUELCH)
V
IH
, Input High Voltage
V
IL
, Input Low Voltage
Input Current
LOGIC OUTPUTS (LOS)
V
OH
, Output High Voltage
V
OL
, Output Low Voltage
Min
2.0
0.8
40
6
2.4
0.4
Typ
Max
Unit
V
V
μA
μA
V
V
Test Conditions/Comments
I
INH
, V
IN
= 2.4 V, 100 kΩ pull-down resistor on-chip
I
INL
, V
IN
= 0.4 V, 100 kΩ pull-down resistor on-chip
Open drain output, 4.7 kΩ to 10 kΩ
pull-up resistor to VCC
Open drain output, 4.7 kΩ to 10 kΩ
pull-up resistor to VCC
Rev. A | Page 4 of 16
ADN2891
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Power Supply Voltage
Minimum Voltage
(All Inputs and Outputs)
Maximum Voltage
(All Inputs and Outputs)
Storage Temperature
Operating Temperature Range
Production Soldering Temperature
Junction Temperature
Rating
4.2 V
VEE − 0.4 V
VCC + 0.4 V
−65°C to +150°C
−40°C to +95°C
J-STD-20
125°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.
THERMAL RESISTANCE
θ
JA
is specified for 4-layer PCB with exposed paddle soldered
to GND.
Table 3.
Package Type
3 mm × 3 mm, 16-lead LFCSP
θ
JA
28
Unit
°C/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. A | Page 5 of 16
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