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11.3 Gbps, Active Back-Termination, Differential VCSEL Driver ADN2530
FEATURES
Up to 11.3 Gbps operation −40°C to +100°C operation Very low power: ISUPPLY = 65 mA Typical 26 ps rise/fall times Full back-termination of output transmission lines Crosspoint adjust function PECL-/CML-compatible data inputs Bias current range: 2 mA to 25 mA Differential modulation current range: 2.2 mA to 23 mA Automatic laser shutdown (ALS) 3.3 V operation Compact 3 mm × 3 mm LFCSP Voltage-input control for bias and modulation currents XFP-compliant bias current monitor
GENERAL DESCRIPTION
The ADN2530 laser diode driver is designed for direct modulation of packaged VCSELs with a differential resistance ranging from 35 Ω to 140 Ω. The active back-termination technique provides excellent matching with the output transmission lines while reducing the power dissipation in the output stage. The back-termination in the ADN2530 absorbs signal reflections from the TOSA end of the output transmission lines, enabling excellent optical eye quality to be achieved even when the TOSA end of the output transmission lines is significantly misterminated. The small package provides the optimum solution for compact modules where laser diodes are packaged in low pin count optical subassemblies. The modulation and bias currents are programmable via the MSET and BSET control pins. By driving these pins with control voltages, the user has the flexibility to implement various average power and extinction ratio control schemes, including closed-loop control and look-up tables. The eye crosspoint in the output eye diagram is adjustable via the crosspoint adjust (CPA) control voltage input. The automatic laser shutdown (ALS) feature allows the user to turn on/off the bias and modulation currents by driving the ALS pin with the proper logic levels. The product is available in a space-saving 3 mm × 3 mm LFCSP specified from −40°C to +100°C.
APPLICATIONS
10 Gb Ethernet optical transceivers 10G-BASE-LRM optical transceivers 8× and 10× Fibre Channel optical transceivers XFP/X2/XENPAK/MSA 300 optical modules SONET OC-192/SDH STM-64 optical transceivers
FUNCTIONAL BLOCK DIAGRAM
VCC VCC VCC CPA ALS
ADN2530
IMODP 100Ω IMOD IMODN VCC
50Ω
50Ω GND
DATAP DATAN
CROSS POINT ADJUST
IBMON IBIAS 800Ω 800Ω
200Ω
200Ω
200Ω
10Ω
05457-001
MSET
GND
BSET
Figure 1.
Rev. A
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ADN2530 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Package Thermal Specifications ................................................. 4 Absolute Maximum Ratings............................................................ 5 ESD Caution.................................................................................. 5 Pin Configuration and Function Descriptions............................. 6 Typical Performance Characteristics ............................................. 7 Theory of Operation ...................................................................... 10 Input Stage................................................................................... 10 Bias Current ................................................................................ 10 Automatic Laser Shutdown (ALS) ........................................... 11 Modulation Current................................................................... 11 Load Mistermination ................................................................. 13 Crosspoint Adjust....................................................................... 13 Power Consumption .................................................................. 13 Applications Information .............................................................. 15 Typical Application Circuit........................................