1
Characteristics subject to change without notice
2053 3.0 10/03/01
SML2108
SUMMIT
MICROELECTRONICS, Inc.
SUMMIT MICROELECTRONICS, Inc., 2001
300 Orchard City Dr., Suite 131
Campbell, CA 95008
Phone 408-378-6461
FAX 408-378-6586
www.summitmicro.com
PRELIMINARY
!
!
!
!
! Dual Closed-loop Control of Laser Diode Mean
Power and Extinction Ratio
!
!
!
!
! Automatic Power Control (APC) with Integrated
10-Bit Programmable Offset
"
""
"
" Automatic Initial Bias Optimization
!
!
!
!
! Integrated Bias Current Monitor
"
""
"
" Monitors & Measures Laser Temperature
Directly
"
""
"
" Eliminates Need for External Thermistor &
Thermal Coupling Issues
"
""
"
" Alarm Output on Over-temperature Condition
!
!
!
!
! Adaptive Modulation Control (AMC)
"
""
"
" Adjusts Modulation Current as a Function of
the Laser Temperature
"
""
"
" 256 Independent Compensation Values
"
""
"
" Integrated 8-Bit Modulation Control DAC
!
!
!
!
! Current Available: 0 to 100mA Sink or Source
!
!
!
!
! Electronic Calibration Through 2-wire Interface
!
!
!
!
! 3V or 5V Operation
!
!
!
!
! Typical Applications: 2.5GHz Transceivers;
200 pin/300 pin 10GIG Sonet MSA Compliant;
10GbE XENPAK-compliant Transponders
Dual Loop Laser Diode Adaptive Power Controller
with Look Up Table
SIMPLIFIED APPLICATION DIAGRAM
FEATURES
The SML2108 is an adaptive power controller for laser
diodes. It is the industry's first integrated device that can
directly monitor and measure a laser diode's temperature,
and provide a variable modulation current. The
SML2108's integrated active feedback loop is used to
calibrate and control the mean and modulation power of
high speed, high power laser diodes.
Inherent manufacturing tolerances introduce variations
of performance in laser diodes. These variations, com-
bined with parametric changes over the laser's extreme
temperature range and laser aging, call for an efficient
temperature compensation scheme. Using an internal
digital control loop and a programmable nonvolatile com-
pensation lookup table, the SML2108 provides the most
optimum adaptive power control with a minimum number
of external components.
The SML2108 removes the need for any manual calibra-
tion of the laser control circuit, which is currently the
industry standard practice. All calibration values are
programmed through the 2-wire communication interface,
which can be controlled by most production ATE equip-
ment.
Programming of configuration, control and calibration
values by the user can be simplified with the interface
adapter and Windows GUI software obtainable from Sum-
mit Microelectronics.
DESCRIPTION
DETECT
SDA
SCL
BIASN
MODN
AUTOMON
VSS
LASER
MODULATION
DRIVER
VDD
2053 SAD
MODSET
IN+
IMOD
SML2108
LASER
DIODE
MONITOR
DIODE
Interface
VDD
VDD
IN
2
SML2108
2053 3.0 10/03/01
SUMMIT MICROELECTRONICS, Inc.
PRELIMINARY
FUNCTIONAL BLOCK DIAGRAM
SCL
CE#
SDA
A0
A1
A2
VSS
VDD
+
1
2
3
4
5
48
6
AUTOMON
DETECT
12
10-Bit
DAC
10-Bit
NV Reg
10-Bit
DAC Reg
Config
8-Bit
NV Reg
8-Bit
ADC
NV Look-up
Table
NV Scaling
& Offset
ADC Read &
Alarm Reg
8-Bit
DAC Reg
8-Bit
DAC
MOD P
MOD N
BIAS P
BIAS N
RDY
VSS A
ALERT#
CAP1
CAP2
11
10
13
7
8
2053 BD 2.2
EXT TEMP
5
VSS D
14
VCC
(All Rs 100k
)
3
2053 3.0 10/03/01
SML2108
SUMMIT MICROELECTRONICS, Inc.
PRELIMINARY
PIN CONFIGURATION
PIN DESCRIPTIONS
DETECT (12)
This is the analog input from the laser monitor photodiode
for the integrator circuit. There is an on-board resistance
of 2M
between the DETECT input and CAP1 pin.
CAP1 and CAP2 (11 & 10)
Capacitor inputs for an external capacitor in the feedback
loop of the Mean Power Control Integrator. There is an on-
board capacitance of 500pF.
AUTOMON (6)
Active high input used to enable the internal auto-monitor
function, which provides automatic adjustments to the
modulation output currents (MODP and MODN) based on
the internal A/D output and the values stored in the
nonvolatile lookup table. This pin has an internal 100k
pull-up.
ALERT# (8)
Active low, open-drain output. This pin is driven low
whenever the bias current increases beyond a predefined
nonvolatile threshold. This can be used to predict laser
failure.
SDA, SCL (4 & 5)
Data and Clock lines, respectively, whose function and
use are based on the industry standard I
2
C interface.
Lookup table values, configuration data, and D/A and A/D
registers may all be accessed via these two pins of the
SML2108. These pins have internal 100k
pull-ups.
A0, A1, A2 (1, 2, & 3)
Address Pins for the interface provided to allow multiple
devices on a single bus. These pins have internal 100k
pull-ups.
A0
A1
A2
SDA
SCL
AUTOMON
RDY#
ALERT#
EXT TEMP
CAP2
CAP1
DETECT
MODN
MODN
BIASN
BIASN
V
SS
V
SS
V
SS
V
SS
BIASN
BIASN
MODN
MODN
48-Pin TQFP
2053 PCon 2.1
V
SS
A
V
SS
D
V
DD
V
DD
BIASP
BIASP
MODP
MODP
V
DD
V
DD
V
SS
V
SS
CE#
V
DD
V
DD
V
DD
BIASP
BIASP
MODP
MODP
V
DD
V
DD
V
SS
V
SS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
36
35
34
33
32
31
30
29
28
27
26
25
48
47
46
45
44
43
42
41
40
39
38
37
4
SML2108
2053 3.0 10/03/01
SUMMIT MICROELECTRONICS, Inc.
PRELIMINARY
RDY# (7)
Active low, open-drain output. This pin is driven low
whenever the internal A/D is performing a conversion, or
while the on-board EEPROM is being programmed.
EXT TEMP (9)
Temperature input (or no connection). This pin can be
programmed as an input to the ADC and can interface a
temperature sensor. The EXT TEMP pin is multiplexed
with the bias current to provide a means of configuring the
input to the ADC. When EXT TEMP is programmed as the
input to the ADC using bit 5 of Register 1, the converted
value of the current entering this pin is used as the
address of the EEPROM lookup table. In this configura-
tion the modulation current can be controlled by tempera-
ture rather than the bias current. Refer to the application
example on using the EXT TEMP pin. If this option is not
used the pin should be left floating.
V
SS
A, V
SS
D (13 & 14)
Analog and digital low-side supplies for on-board cir-
cuitry. Must be at same potential as all other VSS pins.
V
DD
(15, 16, 21, 22, 39, 40, 45, 46, & 47)
High-side supply for the Bias and Modulation currents and
power supply input for the chip.
V
SS
(23, 24, 29, 30, 31, 32, 37, & 38)
Power supply return.
CE# (48)
The chip enable input is active low and provides an
additional method of enabling the serial interface. The
state of this pin has no effect on the auto-monitor function.
This pin has an internal 100k
pull-up.
BIASP (17, 18, 43, & 44)
High-side mean bias control current. Current source
output range is programmable, with the optional ranges of
0 to 100mA or 0 to 10mA.
BIASN (27, 28, 33, & 34)
Low-side mean bias control current. Current sink input
range is 0 to 100mA.
MODP (19, 20, 41, &42)
High-side modulation control current. Current source
output range is programmable, with optional ranges of 0 to
100mA or 0 to 10mA.
MODN (25, 26, 35, &36)
Low-side modulation control current. Current sink input
range is 0 to 100mA.
5
2053 3.0 10/03/01
SML2108
SUMMIT MICROELECTRONICS, Inc.
PRELIMINARY
*COMMENT
Stresses listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions
outside those listed in the operational sections of this specification is not
implied. Exposure to any absolute maximum rating for extended
periods may affect device performance and reliability.
Temperature Under Bias ...................... 55C to 125C
Storage Temperature ........................... 65C to 150C
Lead Solder Temperature (10 secs) ................... 300 C
ELECTRICAL TABLES
ABSOLUTE MAXIMUM RATINGS*
(Over Recommended Operating Conditions; Voltages are relative to GND)
l
o
b
m
y
S
r
e
t
e
m
a
r
a
P
s
n
o
i
t
i
d
n
o
C
.
n
i
M
.
p
y
T
.
x
a
M
s
t
i
n
U
e
c
n
a
m
r
o
f
r
e
P
C
D
A
l
a
c
i
p
y
T
N
/
S
o
i
t
a
r
e
s
i
o
N
o
t
l
a
n
g
i
S
T
A
C
5
2
=
0
7
B
d
D
H
T
n
o
i
t
r
o
t
s
i
d
c
i
n
o
m
r
a
h
l
a
t
o
T
0
8
B
d
n
o
i
t
a
l
u
d
o
m
r
e
t
n
i
c
i
n
o
m
r
a
h
k
a
e
P
n
o
i
t
r
o
t
s
i
d
r
e
d
r
O
d
n
2
0
8
B
d
r
e
d
r
O
d
r
3
0
8
B
d
y
c
a
r
u
c
c
A
C
D
n
o
i
t
u
l
o
s
e
R
8
s
t
i
B
g
n
i
s
s
i
m
o
n
h
c
i
h
w
r
o
f
n
o
i
t
u
l
o
e
R
d
e
e
t
n
a
r
a
u
g
e
r
a
s
e
d
o
c
8
s
t
i
B
y
c
a
r
u
c
c
a
e
v
i
t
a
l
e
R
B
S
L
L
N
D
1
B
S
L
r
o
r
r
e
e
l
a
c
s
ll
u
f
e
v
i
t
i
s
o
P
2
B
S
L
r
o
r
r
e
t
e
s
f
f
o
r
a
l
o
p
i
n
U
V
S
S
V
5
=
2
B
S
L
V
S
S
o
t
V
7
.
2
=
V
6
.
3
2
B
S
L
2053 Elect Table A
RECOMMENDED OPERATING CONDITIONS
Temperature
40
C to 85C.
Voltage
3.0V to 5.5V
PDF 
ZIP