ADN2873

3.3 V, 50 Mbps to 4.25 Gbps, Single-Loop, Laser Diode Driver ADN2873 FEATURES SFP/SFF and SFF-8472 MSA compliant SFP reference design available 50 Mbps to 4.25 Gbps operation Automatic average power control Typical 60 ps output rise/fall time VCSEL, DFB, and FP laser support Bias current range: from 2 mA to 100 mA Modulation current range: from 5 mA to 90 mA Laser fail alarm and automatic laser shutdown (ALS) Bias and modulation current monitoring Voltage setpoint control Resistor setpoint control 3.3 V supply 24-lead 4 mm × 4 mm LFCSP Pin compatible with ADN2870 GENERAL DESCRIPTION Like the ADN2870, the ADN2873 laser diode driver (LDD) is designed for advanced SFP and SFF modules, using SFF-8472 digital diagnostics. The ADN2873 supports NRZ data transmission operation from 50 Mbps up to 4.25 Gbps. With a new alarm scheme, this device avoids the shutdown issue caused by the system transient generated from various lasers. The ADN2873 monitors the laser bias and modulation currents and it provides fail alarms and ALS. Using setup voltages of a microcontroller DAC or a trimmable resistor voltage divider, the ADN2873 can set up a laser optical average output power and extinction ratio. The optical average power control loop consists of an optical feedback from a photodiode, the comparator, and a status holder. The ADN2873 works easily with the Analog Devices, Inc., ADuC7019/ADuC702x family of MicroConverter® devices and with the ADN289x family of limiting amplifiers to make a complete SFP/SFF transceiver chipset solution. The ADN2873 is pin compatible with the ADN2870 dual-loop LDD, allowing the same design to work with either device. For dual-loop control applications, refer to the ADN2870 data sheet. The product is available in a space-saving 24-lead, 4 mm × 4 mm LFCSP specified over the −40°C to +85°C temperature range. Figure 1 shows an application diagram of the voltage setpoint control with single-ended laser interface. Figure 36 shows a differential laser interface. APPLICATIONS 1×/2×/4× Fibre Channel SFP/SFF modules Multirate OC3 to OC48-FEC SFP/SFF modules LX-4 modules DWDM/CWDM laser transmitters HDTV (SMPTE family) laser transmitters APPLICATIONS DIAGRAM VCC Tx_DISABLE Tx_FAULT VCC MPD ANALOG DEVICES MICROCONTROLLER DAC ADC 1kΩ GND DAC ERREF ERSET 1kΩ GND VCC GND 1kΩ GND 470Ω GND 07493-001 VCC VCC L VCC LASER FAIL ALS IMODN R IMODP DATAP DATAN VCC IBIAS ×100 IMOD CCBIAS RZ PAVSET PAVREF RPAV CONTROL 100Ω ADN2873 IBMON IMMON PAVCAP GND NC Figure 1. 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: 781.461.3113 ©2008 Analog Devices, Inc. All rights reserved. ADN2873 TABLE OF CONTENTS Features .............................................................................................. 1  Applications ....................................................................................... 1  General Description ......................................................................... 1  Applications Diagram ...................................................................... 1  Revision History ............................................................................... 2  Specifications..................................................................................... 3  SFP Timing Specifications........................................................... 5  Absolute Maximum Ratings............................................................ 6  ESD Caution .................................................................................. 6  Pin Configuration and Function Descriptions ............................. 7  Typical Performance Characteristics ............................................. 8  Single-Ended Output ................................................................... 8  Differential Output ....................................................................... 9  Performance Characteristics ..................................................... 10  Optical Waveforms ......................................................................... 12  Theory of Operation ...................................................................... 13  Laser Control .............................................................................. 13  Control Methods ........................................................................ 13  Voltage Setpoint Calibration ..................................................... 13  Resistor Setpoint Calibration .................................................... 15  IMPD Monitoring .......................................................................... 15  Loop Bandwidth Selection ........................................................ 16  Power Consumption .................................................................. 16  Automatic Laser Shutdown (TX_Disable) .............................. 16  Bias and Modulation Monitor Currents.................................. 16  IBIAS Pin ..................................................................................... 16  Data Inputs .................................................................................. 17  Laser Diode Interfacing ............................................................. 17  Alarms.......................................................................................... 18  Outline Dimensions ....................................................................... 19  Ordering Guide .......................................................................... 19  REVISION HISTORY 6/08—Revision 0: Initial Version Rev. 0 | Page 2 of 20 ADN2873 SPECIFICATIONS VCC = 3.0 V to 3.6 V. All specifications TMIN to TMAX1, unless otherwise noted. Typical values are specified at 25°C. Table 1. Parameter LASER BIAS CURRENT (IBIAS) Output Current IBIAS Compliance Voltage IBIAS when ALS Is High MODULATION CURRENT (IMODP, IMODN)2 Output Current IMOD Compliance Voltage IMOD when ALS Is High Rise Time Single-Ended Output2, 3 Fall Time Single-Ended Output2, 3 Random Jitter Single-Ended Output2, 3 Deterministic Jitter Single-Ended Output3, 4 Pulse Width Distortion2, 3 Single-Ended Output Rise Time Differential Output3, 5 Fall Time Differential Output3, 5 Random Jitter Differential Output3, 5 Deterministic Jitter Differential Output3, 6 Pulse Width Distortion Differential Output3, 5 Rise Time Differential Output3, 5 Fall Time Differential Output3, 5 Random Jitter Differential Output3, 5 Deterministic Jitter Differential Output3, 7 Pulse Width Distortion Differential Output3, 5 AVERAGE POWER SET (PAVSET) Pin Capacitance Voltage Photodiode Monitor Current (Average Current) EXTINCTION RATIO SET INPUT (ERSET) Resistance Range AVERAGE POWER REFERENCE VOLTAGE INPUT (PAVREF) Voltage Range Photodiode Monitor Current (Average Current) EXTINCTION RATIO REFERENCE VOLTAGE INPUT (ERREF) Voltage Range ERREF Voltage to IMOD Gain DATA INPUTS (DATAP, DATAN)8 Input Voltage Swing (Differential) Input Impedance (Single-Ended) LOGIC INPUTS (ALS) VIH VIL ALARM OUTPUT (FAIL)9 VOFF VON Min 2 1.2 Typ Max 100 VCC 0.1 90 VCC 0.1 104 96 1.1 35 30 Unit mA V mA mA V mA ps ps ps (rms) ps ps ps ps ps (rms) ps ps ps ps ps (rms) ps ps pF V μA kΩ kΩ V μA V mA/V V p-p Ω V V V V Voltage required at FAIL for IBIAS and IMOD to turn off when FAIL asserted Voltage required at FAIL for IBIAS and IMOD to stay on when FAIL asserted Conditions/Comments 5 1.5 60 60 0.8 19 21 47.1 46 0.64 12 2.1 56 55 0.61 17 1.6 5 mA < IMOD < 90 mA 5 mA < IMOD < 90 mA 5 mA < IMOD < 90 mA 5 mA < IMOD < 90 mA 20 mA < IMOD < 90 mA 20 mA < IMOD < 90 mA 5 mA < IMOD < 30 mA 5 mA < IMOD < 30 mA 5 mA < IMOD < 30 mA 5 mA < IMOD < 30 mA 5 mA < IMOD < 30 mA 5 mA < IMOD < 90 mA 5 mA < IMOD < 90 mA 5 mA < IMOD < 90 mA 5 mA < IMOD < 90 mA 5 mA < IMOD < 90 mA 1.1 50 1.5 0.99 0.07 70 0.05 1.2 80 1.3 1200 25 1.01 1 1000 0.9 Resistor setpoint mode Resistor setpoint mode Voltage setpoint mode Voltage setpoint mode (RPAV fixed at 1 kΩ) Voltage setpoint mode (RPAV fixed at 1 kΩ) Voltage setpoint mode (RERSET fixed at 1 kΩ) 1 100 0.4 50 2 0.8 >1.8 1.2 V typical (±10% tolerance) Alarm if >2.0 V Alarm if shorted to VCC (the alarm is valid for voltage setting mode only) Ignore Undervoltage or Short to GND Condition Ignore Alarm if