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3.3 V Dual-Loop, 50 Mbps to 3.3 Gbps 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.
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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
Protected by U.S. Patent 6,414,974.
APPLICATIONS DIAGRAM
VCC VCC Tx_FAULT Tx_FAIL VCC MPD FAIL ALS IMODN VCC VCC L R IMODP DATAP ANALOG DEVICES MICROCONTROLLER DAC ADC PAVSET IMOD PAVREF CONTROL RPAV 1kΩ GND ERREF IBIAS CCBIAS IBIAS 100Ω DATAN VCC RZ LASER
DAC
ADN2872
1kΩ GND VCC GND GND 1kΩ GND 470Ω GND GND
08013-001
ERSET IBMON IMMON PAVCAP ERCAP
Figure 1.
Rev. 0
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ADN2872
TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 General Description ......................................................................... 1 Applications Diagram ...................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 SFP Timing Specifications........................................................... 4 Absolute Maximum Ratings............................................................ 5 ESD Caution .................................................................................. 5 Pin Configuration and Function Descriptions ............................. 6 Typical Performance Characteristics ............................................. 7 Optical Waveforms ........................................................................... 9 Theory of Operation ...................................................................... 10 Dual-Loop Control..................................................................... 10 Control ......................................................................................... 11 Voltage Setpoint Calibration ..................................................... 11 Resistor Setpoint Calibration .................................................... 13 IMPD Monitoring .......................................................................... 13 Loop Bandwidth Selection ........................................................ 14 Power Consumption .................................................................