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
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
user are simplified with the I
2
C interface adapter
(SMX3200) and Windows Programming software available
from Summit Microelectronics.
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
2
C 2-wire serial bus interface for programming
• I
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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SIMPLIFIED APPLICATION DRAWING
DATA+
DATA–
+3.3V
MODSET
25
24
15
VHI
ILU0
13
OUT+
Typical
Laser Driver
CAPC
APCSET
BIASMAX
OUT–
V
DD
No Connects
V
DD
(+3.3V)
VDD
VDD
Address = 0
VBRIDGE
12
NTC
2
3
4
5
6
7
A1
A2
THERMISTOR
11
LD
SML2120
BIAS
EXT_TEMP
ILU1
MPD
C2
20
23
14
18
16
C
INT
Typical Laser
Diode with
Photo Diode
and Thermistor
MPD
SDA
SCL
AM#
ALERT#
VLO W
ENA#
VAPC
VSS
VSS
VSS
C1
17
R
INT
10
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 1/22/04
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SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
