Programmable Adaptive Laser Power Controller with Dual Lookup Tables

© 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 1/22/04

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SML2120

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FEATURES AND APPLICATIONS

Features:

• 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

configuration, control values, monitoring, and

operational status - 100KHz and 400KHz

• Small 5X5 28-Pin QFN Package

Applications:

• Laser power management for Telecom/Datacom

motherboards

• Direct modulation and electro-absorptive modulation

applications

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INTRODUCTION

The SML2120 is an advanced, programmable laser diode

power controller ideal for optical networking applications.

The integrated automatic power control (APC) circuit adapts

to variations in the laser’s power output as detected by a

photo diode.

The SML2120 drives two low current outputs derived from

values stored in independent 256x8 Lookup Tables. The low

current outputs are suitable for controlling the MODSET

input of typical laser driver IC’s. The input stimulus for each

Lookup Table can be configured as the laser temperature,

the bias current, or an external signal. Characteristics of the

laser’s performance over time and temperature are stored

in the lookup tables, allowing the outputs to adapt to system

conditions and optimize overall performance.

Programming of configuration and control values by the

(SMX3200) and Windows Programming software available

from Summit Microelectronics.

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SIMPLIFIED APPLICATION DRAWING

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

SML2120

V

ILU1

THERMISTOR

14

11

20

18

BIAS

MPD

16

17

C1

C2

13

15

24

25

VDD

VHI

+3.3V

2

3

4

5

A1

A2

SDA

SCL

6

7

AM#

ALERT#

DATA–

DATA+

MODSET

BIASMAX

APCSET

CAPC

V

DD

OUT–

OUT+

Typical

Laser Driver

Typical Laser

Diode with

Photo Diode

and Thermistor

ILU0

C

INT

R

INT

12

VBRIDGE

NTC

LD

MPD

VDD

EXT_TEMP

23

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