ANALOG DEVICES ADN2872 Service Manual
3.3 V Dual-Loop, 50 Mbps to 3.3 Gbps
V
FEATURES
SFP/SFF and SFF-8472 MSA compliant
SFP reference design available
Any rate from 50 Mbps to 3.3 Gbps operation
Dual-loop control of average power and extinction ratio
Typical rise/fall time: 60 ps
Bias current range: 2 mA to 100 mA
Modulation current range: 5 mA to 90 mA
Laser FAIL alarm and automatic laser shutdown (ALS)
Bias and modulation current monitoring
3.3 V operation
4 mm × 4 mm LFCSP
Voltage setpoint control
Resistor setpoint control
APPLICATIONS
Multirate OC3 to OC48-FEC SFP/SFF modules
1×/2×/4× Fibre Channel SFP/SFF modules
LX-4 modules
DWDM/CWDM SFP modules
1GE SFP/SFF transceiver modules
Laser Diode Driver
ADN2872
GENERAL DESCRIPTION
Like the ADN2870, the ADN28721 laser diode driver is designed
for advanced SFP and SFF modules, using SFF-8472 digital
diagnostics. The device features dual-loop control of the average
power and extinction ratio, which automatically compensates
for variations in laser characteristics over temperature and aging.
The laser needs only be calibrated at 25°C, eliminating the need
for expensive and time consuming temperature calibration. The
ADN2872 supports single-rate operation from 50 Mbps to
3.3 Gbps, or multirate operation from 155 Mbps to 3.3 Gbps.
With a new alarm scheme, this device avoids the shutdown issue
caused by the system transient generated from various lasers.
The average power and extinction ratio can be set with a
voltage provided by a microcontroller DAC or by a trimmable
resistor. The part provides both bias and modulation current
monitoring, as well as fail alarms and automatic laser shutdown.
The ADN2872, a SFF-/SFP-compliant laser diode driver, can
work with the Analog Devices, Inc., ADuC7019/ADuC702x
MicroConverter® family and the ADN289x limiting amplifier
family, to form a complete SFP/SFF transceiver solution. The
ADN2872 is available in a space-saving 4 mm × 4 mm LFCSP
specified over the −40°C to +85°C temperature range.
Figure 1 shows an application diagram with a microcontroller
interface.
1
Protected by U.S. Patent 6,414,974.
APPLICATIONS DIAGRAM
Tx_FAULT
Tx_FAIL
ANALOG DEVICES
MICROCONTROLLER
DAC
ADC
DAC
Rev. 0
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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1kΩ
1kΩ
V
GND
GND
CC
MPD
PAVSET
PAVREF
RPAV
ERREF
ERSET
VCC
CC
GND
GND GND
Figure 1.
V
ERCAP
CC
L
R
IMODP
IBIAS
CCBIAS
V
CC
LASER
DATAP
DATAN
V
CC
R
Z
08013-001
ALSFAIL
I
CONTROL
IBMON IMMON
I
470Ω1kΩ
MOD
BIAS
V
CC
IMODN
ADN2872
PAVCAP
GND
100Ω
GND
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 ©2009 Analog Devices, Inc. All rights reserved.
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