3.3 V Dual-Loop, 50 Mbps to 3.3 Gbps
Laser Diode Driver
ADN2872
Rev. 0
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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
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
ANALOG DEV I CES
MICROCONTROLLER
Tx_FAULT
Tx_FAIL
CONTROL
PAVREF
PAVSET
ADN2872
RPAV
GND
DAC
DAC
V
CC
MPD
ERREF
ERSET
GND
I
MOD
DATAP
IMODP
DATAN
I
BIAS
IMODN
IBMON IMMON
ALSFAIL
IBIAS
100Ω
CCBIAS
V
CC
LASER
L
R
V
CC
V
CC
VCC
GND GND
PAVCAP
470Ω1kΩ
GND
GND
ERCAP
GND
1kΩ
1kΩ
ADC
CC
V
CC
R
Z
08013-001
Figure 1.