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SML2120 Programmable Adaptive Laser Power Controller with Dual Lookup Tables

Preliminary Information

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(See Last Page)

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FEATURES AND APPLICATIONS INTRODUCTION Features: The SML2120 is an advanced, programmable laser diodepower controller ideal for optical networking applications. The integrated automatic power control (APC) circuit adaptsto variations in the laser’s power output as detected by aphoto diode.The SML2120 drives two low current outputs derived fromvalues stored in independent 256x8 Lookup Tables. The low current outputs are suitable for controlling the MODSETinput of typical laser driver IC’s. The input stimulus for eachLookup Table can be configured as the laser temperature,the bias current, or an external signal. Characteristics of thelaser’s performance over time and temperature are stored in the lookup tables, allowing the outputs to adapt to systemconditions and optimize overall performance.Programming of configuration and control values by theuser are simplified with the I

•Integrated Automatic Power Control (APC) circuit•100 mA bias current sink capability•Dual low-current outputs (up to 2.5 mA) based on two independent 256x8 Lookup Table values•Bias current and/or temperature monitoring capability•Dual high/low alert registers•Advanced lookup algorithm eliminates unnecessary output changes•Flexible voltage operation; 0 to 5V, 0 to 3.3V, or -5.2V to +3.3V•I

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C 2-wire serial bus interface for programming configuration, control values, monitoring, and operational status - 100KHz and 400KHz•Small 5X5 28-Pin QFN Package

Applications :

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•Laser power management for Telecom/Datacom motherboards•Direct modulation and electro-absorptive modulation applications

C interface adapter(SMX3200) and Windows Programming software available from Summit Microelectronics.

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SIMPLIFIED APPLICATION DRAWING

TypicalLaser Driver

V
DD (+3.3V) DATA–DATA+
No Connects MODSETBIASMAXAPCSETCAPCV OUT–OUT+
DD 25VDDVHI+3.3V 13 24 15 12VBRIDGENTCLDMPD VDD 11 2 3
Address = 0

SML2120

20 4 EXT_TEMP 23 5A1A2SDASCL ILU1 THERMISTOR 14 18BIASMPD 6 16 7AM#ALERT# C
INT Typical LaserDiode withPhoto Diodeand Thermistor ILU0 C1C2 17
VSSVSS VAPC ENA# VSS R
INT 1 8VLOW 9 22 10 21

Figure 1. Typical SML2120 Connections to a Laser Driver and Laser Diode

Note: This is an applications example only. Some pins, components and values are not shown.

© SUMMIT Microelectronics, Inc. 2004 • 1717 Fox Drive • San Jose CA 95131-2312 • Phone 408 436-9890 • Fax 408 436-9897 • www.summitmicro.com 2066 6.3 1/22/041