Analog Technologies ATLS500MA103 User manual

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nalog Technologies ATLS500MA103
Low Noise Constant Current Laser Controller
Figure 1. Physical Photo of ATLS500MA103S
FEATURES
Ultra Low Noise: <5μA*
High Current without Heat Sink: 500mA
High Absolute Accuracy: <0.1%
High Stability: <100ppm/°C
Dual Modulation Ports: High and Low Speed
Complete Shielding
Compact Size
100 % Lead (Pb)-free and RoHS Compliant
DIP and SMT Packages Available
*Total RMS between 0.1Hz to 0.5MHz.
APPLICATIONS
Driving laser diodes with low noise, including DPSSL,
EDFA, SOA, fiber laser, direct diode lasers, etc.
DESCRIPTION
The is an electronic module designed for driving diode
lasers with up to 500mA low noise current. Figure 1 shows
physical photo of .The output voltage is 1.5V to 4V when
powered by a 5V power supply.
When the maximum power consumed by the controller is
maintained to <1W, it does not require a heat sink to operate.
The controller has temperature compensation network so that
the output current maintains the same even as the controller
temperature rises.
In case the controller temperature exceeds a preset limit, 120°C,
the controller will be shut down by itself to prevent the
controller from being damaged by the over heat.
The output current of the can be set by an input voltage
linearly or modulated by an external signal of up to 2MHz in
bandwidth, resulting in a minimum 1μS rise and fall times at
the output current.
A highly stable low noise 2.5V reference voltage is provided
internally for setting the output current. This reference can also
be used as the voltage reference for external ADCs (Analog to
Digital Converters) and/or DACs (Digital to Analog
Converters) which are utilized for converting the analog signals,
such as LIO which represents the output current, into digital
signals, and/or converting the digital signals into analog ones
for setting the analog voltages, such as LIS which sets the
output current.
The is packaged in a 6 sided metal enclosure, which blocks
EMIs (Electro-Magnetic Interferences) to prevent the controller
and other electronics from interfering each other.
There are 2 packaging versions available: DIP through hole
package and surface mount type.
Warning: Both the surface mount and the through hole
types of modules can only be soldered manually
on the board by a solder iron of < 310ºC (590ºF),
not go through a reflow oven process.
Figure 2. Pin Names and Locations
Figure 2 is the actual size top view of the , which shows the pin
names and locations. Its thickness is 5mm. Table 1 shows the
pin function descriptions.
Table 1. Pin Function Descriptions
Pin # Pin Name Pin Type Description
1 SDN Digital input
For ATLS500mA103: Shut down control. Negative logic.
For ATLS500mA103-PD: Shut down control. Positive logic. There is a pull-down
resistor of 100K to the ground.
2 GND Signal ground Signal ground pin. Connect ADC and DAC grounds to here.
20
VPS
PGND
LDC
LDA
TMPO
LPGD
GND
2.5V
R
LILM
LIS
LIO
SDN 1
3
4
5
6
2
12
10
9
8
7
11
14.5

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nalog Technologies ATLS500MA103
Low Noise Constant Current Laser Controller
3 2.5VR Analog output
2.5V reference voltage. It is used by the internal DACs as the reference voltage. It can
source 3mA max, with 5μVp-p noise @ 0.1 to 10 Hz and 25ppm/°C stability max.
4 LILM Analog input Laser current limit set. 0V to 2.5V sets the laser current limit from 0 to 550mA linearly.
5 LIS Analog input Laser current set. 0V to 2.5V sets the laser current from 0 to 500mA linearly.
6 LIO Analog output
Laser current output indication. 0V to 2.5V indicates the laser current of from 0A to
500mA linearly.
7 LPGD Digital output
Loop good indication. When the controller is working properly, this pin is pulled high.
Otherwise, it is pulled low.
8 TMPO Analog output The driver internal temperature indication output. Operating internally temperature.
9 LDA Analog output
Laser diode anode. Connect it to the anode of the laser diode. This pin is used to drive a
laser of which the cathode is connected to the case and the case is connected to the
ground. See below Figure 4.1, 4.2 or Figure 5.
10 LDC Analog output
Laser diode cathode. Only connect to the cathode of the laser diode. See below Figure
4.1, 4.2 or Figure 5.
11 PGND Power ground Power ground pin. Connect it directly to power supply return rail.
12 VPS Power input Power supply. The driver works from 3.0V to 5.5V.
SPECIFICATIONS
Table 2. Characteristics (Tambient = 25°C)
Parameter Value Unit/Note
Maximum output current 500 mA
Output current noise
(0.1Hz to 0.5MHz RMS) <5 μA
Current set voltage range 0 ~ 2.5 V
Current limit set voltage range 0 ~ 2.5 V
Modulation response bandwidth 2 MHz
Minimum drop out voltage 0.3 +
5×Iout V
Power supply voltage range 3.0 ~ 5.5 V
Operating case temperature −40 ~ 125 °C
Rise and fall times 300 nS
OPERATION PRINCIPLE
The block diagram of the controller is shown in Figure 3.
The shut down control circuit is activated under one of these
3 circumstances: external shut down, output current exceeds
the current limit, and the internal temperature exceeds
120°C.
When the controller is shut down by the external shutdown
signal, it will restart upon detecting the releasing of the
shutdown signal.
When it is shut down by the over current limit, the controller
shuts down itself and restarts again by going through the
soft-start process immediately. Therefore, the output current
has a saw-tooth waveform: quick shut down, slow and ramp
up.
When the controller is shut down by the over temperature, it
will wait till the temperature goes below the temperature limit,
120°C. Usually it takes a few or tens of seconds for the
controller to cool down before it restarts itself, depending on
the thermal mass of the controller and its surrounding
mechanical parts attached thermally, such as the PCB and its
traces, the heat-sinks if any, etc.
When controller is shut down, the voltage reference is also shut
down.
TMPO
Laser
Diode
8
10
5
LDC
LIS
Shut-
down
& soft-
start
circuit
Current
sensor &
low noise
driver
Voltage
reference
12
3
2
1
LISL
GND
SDN
10pF
100KΩVPS
11
PGND
4
6
LIO
LILM
LPGD
7
Temp.
sensor
9
LDA
Current
limiter
Figure 3. Block Diagram
APPLICATIONS
Figure 4.1 and 4.2 shows a typical application circuit. W1 and
W2 set the output current limit and output current respectively.
Resistor R1 and capacitor C1 form a low pass filter, to lower
the noise from the voltage reference.
2.5V
R

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nalog Technologies Low Noise Constant Current Laser Controller
ATLS500MA103
Laser diode D1 is connected between LDA and PGND. It is
worth mentioning that the power supply return terminal
should be connected to the pin 11 PGND and the cathode of
the laser diode should be connected to the pin 10 PGND. These
2 nodes should not be connected together externally and they
are connected together internally already by the controller.
Power Supply 0V
(Clock-wise)
Power Supply 5V
S1 SPST
D1
Laser Diode
Shut Down
Loop Good Indication
Current Limit Set
LIO
6
VPS 12
PGND 10
LPGD 7
LDA 9
GND
2
LIS
5
PGND 11
TMPO 8
2.5VR
3
LILM
4
SDN
1
Laser Controller
1 2
C1
1uF to 10uF
Current Set
To ADC
To ADC
(Clock-wise)
3
2
1
W1
20K
3
2
1
W2
20K
1 2
R1 1M 2 1
D2 LED
Figure 4.1 Typical Stand-alone CW Operation Schematic for
Power Supply 0V
(Clock-wise)
Power Supply 5V
S1 SPST
D1
Laser Diode
Shut Down
Loop Good Indication
Current Limit Set
LIO
6
VPS 12
PGND 10
LPGD 7
LDA 9
GND
2
LIS
5
PGND 11
TMPO 8
2.5VR
3
LILM
4
SDN
1
Laser Controller
1 2
C1
1uF to 10uF
Current Set
To ADC
To ADC
(Clock-wise)
3
2
1
W1
20K
3
2
1
W2
20K
1 2
R1 1M 2 1
D2 LED
Figure 4.2. Typical Stand-alone CW Operation Schematic for ATLS500MA103-PD
Turning the Controller On and Off
The controller can be turned on and off by setting the SDN
pin high and lower respectively. It is recommended to turn
the controller on by this sequence:
To turn on: For ATLS500MA103, turn on the power by
providing the power supply voltage to the controller, turn on
the controller by releasing the SDN pin. For
ATLS500MA103-PD, turn on the power by providing the
power supply voltage to the controller, turn on the controller
by connecting the SDN pin to VPS.
To turn off: turn off the controller by lowering the voltage
of SDN pin, turn off the power by stopping the voltage
supply on the VPS pin.
When not controlling by the SDN pin: leave it unconnected
and turn on and off the controller by the power supply.
In Figure 4.1 and 4.2, S1 is the shut down switch. For
ATLS500MA103, the internal equivalent input circuit of
SDN pin is a pull-up resistor of 100K being connected to
VPS in parallel with a 10pF capacitor to the ground. For
ATLS500MA103-PD, the internal equivalent input circuit of
SDN pin is a pull-down resistor of 100K being connected to
the ground in parallel with a 10pF capacitor to the ground. The
switch S1 can also be an electronic switch, such as an I/O pin
of a micro-controller, with an either open drain or push/pull
output. If not using a switch (S1) to control the laser, leave the
SDN pin unconnected. D2 is an LED, indicating when the
control loop works properly, that is: the output current equals
to the input set value. This pin has an internal pull up resistor
of 5K to the power supply pin, VPS, pin 10. The pull down
resistance is 200Ω. This 5K resistor can drive a high efficiency
LED directly. When higher pull up current is needed for
driving such as a higher current LED, an external resistor can
be placed between the VPS and the LPGD pins. Make sure
that the resistor is not too small that the pull down resistor will
not be able to pull the pin low enough when the controller loop
is not good. When choosing not to use an LED for indicating
the working status, leave the LPGD pin unconnected.
The LPGD pin can also be connected to a digital input pin of a
micro-controller, when software/firmware is utilized in the
system.
LDC
LDC

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nalog Technologies Low Noise Constant Current Laser Controller
ATLS500MA103
Setting the Output Current
The output current limit is set by adjusting W1, which sets
input voltages of LILM, pin 4. The output current will be:
I_output = 550 ×LILM (V)/2.5V (mA).
LILM should never be left float. Otherwise, the output
current limit may be set to too high a value that the laser
might be damaged.
The output current is set by adjusting W2, which sets input
voltages of LIS, pin 5. The output current will be:
I_output = 500 ×LIS (V)/2.5V (mA).
When no modulation is needed, it is suggested to use an RC
low-pass-filter, the R1 and C1 in Figure 4.1, to lower the
AC noise from the voltage reference source. The time
constant of this filter can be between a few to 10’s of
seconds. The bigger the time cost, the lower the output noise,
but the longer time will be needed to wait the output current
to go up.
Both of LILM and LIS, only LIS, can be configured by
using a DAC, to replace the W1 and W2 in Figure 4.1. Make
sure that the DAC has output low noise, or, if no modulation
is needed, an RC low pass filtered by be inserted between the
DAC and the LIS pin, similar as shown in Figure 4.1.
The LIS allows modulating the output current by a signal of up
to 350 KHz in bandwidth. That is, when using a sinewave
signal to modulate the LIS pin, the output current response
curve will be attenuated by 3dB, or 0.71 times the full response
magnitude in current. When using an ideal square-wave to
modulate the output current at the LIS pin, the rise and fall
time of the output current will be about 1μS.
When the modulation signal is a square-wave and low output
noise is require, the low-pass-filter can still be used for
lowering the output noise. Figure 5 shows such a circuit. The
resistor R1 can be 10K to 1M, depending on the error voltage
caused by the switch leakage current. The LILM pin can be set
by a POT as shown in Figure 4 or connect to 2.5VR.
It is recommended not to set the LIS pin to 0V, but keep
it >0.05V at all the time. The reason is that the laser diode
usually has a junction voltage of 2.5V, when setting the LIS
pin voltage to 0V, the output voltage will warble between 0V
and 2.5V, cause some oscillation slightly.
Power Supply 0V
Power Supply 5V
D1
Laser Diode
Loop Good Indication
Current Limit Set
LIO
6
VPS 12
PGND 10
LPGD 7
LDA 9
GND
2
LIS
5
PGND 11
TMPO 8
2.5VR
3
LILM
4
SDN
1
Laser Controller
1 2
C1
1uF to 10uF
Current Set
To ADC
To ADC
3
2
1
W1
20K
3
2
1
W2
20K
1 2
R1 100K
Digital Modulation Signal Input
S1 SPDT
To Microcontroller
2 1
D2 LED
(Clock-wise)
(Clock-wise)
Figure 5. Low Noise Digital Modulation Circuit
The LIO can still be used to monitor the output current when
the LIS is modulated. The bandwidth of the LIO signal
is >10MHz, more than enough for monitoring output current
modulated by the LIS signal.
Figure 6. Relationship between VPS and LDAMAX
Maximum LDA Output Voltage vs. Power Supply Voltage
The maximum LDA pin output voltage is depending on the
power supply input voltage, VPS. Their relationship is shown
in Figure 6. Therefore, it is recommended that:
VPS ≥V_LD_max + 1V,
Where V_LD_Max is the laser diode’s maximum possible
forward voltage at the operation current.
Monitoring the Output Current
The output current of the controller can be monitored by
measuring the voltage on the LIO pin. This feature is very
useful for micro-controller based system where the ADC is
available and monitoring the current in real time is required.
This pin provides a very low noise voltage signal which is
proportional to the output current:
LIO (V) = I_out ×5(V).
LDC
VPS(V)
LDAMAX
(V)
5.543.3
2.6
3.3
4.9

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nalog Technologies Low Noise Constant Current Laser Controller
ATLS500MA103
For example, when the output signal equals to 2.5V, the
output current is 500mA.
The output impedance of this pin is 10Ωand it can be used to
drive an ADC directly.
It can also be measured by a multimeter during debugging
process.
Figure 7 below shows the relations among LIS, LIMS and
IOUT
Figure 7. LIS & LIO
When LIS ≤LIMS, IOUT changes with LIS linearly; when LIS
＞ILMS, IOUT oscillates between 0 and LIMS.
Monitoring the Controller Internal Temperature
The controller internal temperature can be monitored by
measuring the TMPO pin voltage. The relationship between
the LMPO voltage and the temperature is:
)(
479.3
8015.1
4182.21004.1525 3C
TMPO
T°
−
++−= (1)
where TMPO is the voltage on the TMPO pin.
This formula can be approximated by a linear equation:
)(31.907.192 CTMPOT °×−= (2)
Within the most commonly used temperature range of
between 0°C to 100°C, the maximum error occurs at about
1.5V, at which the temperature error between the calculated
data by using the formula (1) and the approximated data
obtained by using the linear equation (2) is about 0.4°C, with
the linear data being a little lower. The curves of the 2 sets of
the data are plotted in Figure 13.
Please notice that the TMPO pin has a weak driving
capability: the maximum sourcing current is 1μA and the
maximum sinking current is 40μA.
The TMPO pin can also be used as an input control pin: when
forcing the TMPO voltage to below 0.4V, the laser controller
will be shut down.
Controller Power Consumption
The power consumption of the controller can be calculated by:
P_controller = I_output ×(VPS – VLDA),
where I_output is the output current;
VPS is the power supply voltage;
VLDA is the voltage across the laser diode.
When the P_controller exceeds 1W, a heat sink might be
needed. Under this situation, if prefer not to use the heat sink,
this is an option: lowering the controller power consumption
by reducing the power supply voltage VPS.
First Time Power Up
Laser is a high value and vulnerable device. Faults in
connections and damages done to the controller during
soldering process may damage the laser permanently.
To protect the laser, it is highly recommend to use 3 to 4
regular diodes of >200mA to form a “dummy laser” and insert
it in the place of the real laser diode, when powering up the
controller for the first time. Use an oscilloscope to monitor
the LDA voltage at times of power-up and power-down, make
sure that there is not over-shoot in voltage. At the same time,
use an ammeter in serious with the dummy laser, to make sure
that the output current is correct.
After thorough checking free of faults, disconnect the dummy
laser and connect the real laser in place.
The controller output voltage range for the laser is between
0.5 to 4V when powered by a 5V power supply.
Driving High Voltage Laser Diodes
Some laser diodes have high forward voltage, such as 7V,
while the laser driver ATLS1A103D has a maximum output
voltage of 4V. This section tells a way to drive such laser
diodes by using this laser driver.
The schematic is show as in Figure 8. Where Power Supply 1
is the power supply for the laser driver, Power Supply 2 is for
increasing the laser driver's maximum output voltage.
Please notice that the power on sequence has to be in this
way: turn on Power Supply 1, turn on Power Supply 2, then
turn on the laser driver by driving SDN (Shutdown) pin to
logic high.
The sequence for turning off the laser circuit is: turn off the
SDN pin by pulling it down to the logic low, turn off Power
Supply 1, then, turn off power supply 2.
To make sure the circuit works ok: turn on the laser, measure
LDA voltage, it should be between 1V to 3V, at room
temperature, the ideal LDA voltage is around 2V.

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nalog Technologies Low Noise Constant Current Laser Controller
ATLS500MA103
Figure 8. Driving High Voltage Laser Diodes
MECHANICAL DIMENSIONS AND MOUNTING
The ATLS500MA103 comes in 2 packages: through hole
mount and surface mount. The former is often called DIP
(Dual Inline package) or D (short for DIP) package and has
a part number: ATLS500MA103D, and the latter is often
called SMT (Surface Mount Technology) or SMD (Surface
Mount Device) package and has a part number:
ATLS500MA103S. See below Figure 9 and 10.
20
1
3
4
5
6
2
12
10
9
8
7
11
14.5
R1.0×4
2
R1.0×2
Top View Side View
End View
5.0
12
Pin size: 0.5×0.5 4.0
R1.0×2
Unit: mm
Figure 9. Dimensions of the DIP Package Controller
Top View Side View
End View
5.6
16.8
Pin size: 0.5×0.5
R1.0×2
R1.0×4
20
14.5
1
3
4
5
6
2
12
10
9
8
7
11
1.15
2
R1.0×2
11.5
5.0
Unit: mm
Figure 10. Dimensions of the SMT Package Controller
Figure 11 shows the foot print which is seen from the top side
of the PCB, therefore, it is a “see through” view.
Figure 12 shows the view of the bottom side PCB foot-print.
“Tent” (i.e. cover the entire via by the solder mask layer) all
the vias under the controller, otherwise, the vias can be shorted
by the bottom plate of the controller which is internally
connected the ground.
Please notice that, in the recommended foot print for the DIP
package, the holes for pin 2 to 6, and 8 to 12 have larger holes
than needed for the pins. This arrangement will make it easier
for removing the controller from the PCB, in case there is a
rework needed. The two smaller holes, for pin 1 and 7, will
hold the controller in the right position.
It is also recommended to use large copper fills for VPS,
PGND, and the LDC pins, and other pins if possible, to
decrease the thermal resistance between the module and the
supporting PCB, to lower the module temperature.
Please be notice that the SMT version cannot be soldered by
reflow oven. It must be soldered manually.
20
1.5 ×14
1.0 ×12 0.8 ×2
12
14.5
2 ×14
R1.0 ×4
PCB Copper
without solder pad
PCB Hole
Orientation Mark Outline
Figure 11. Top Side PCB Foot-print for the DIP Package

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nalog Technologies Low Noise Constant Current Laser Controller
ATLS500MA103
3.0 ×14
1.5 ×14
PCB Copper
with solder pad
Figure 12. Top View of the Bottom Side PCB Foot-print
Figure 13. Controller Internal Temperature vs. TMPO Voltage

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nalog Technologies Low Noise Constant Current Laser Controller
ATLS500MA103
WARNING: Both the surface mount and the through hole types of modules can only be soldered manually on the board
by a solder iron of < 310ºC (590ºF), not go through a reflow oven process.
NOTE: The power supply may have overshoot, when happens, it may exceed the maximum allowed input voltage, 6V,
of the controller and damage the controller permanently. To avoid this from happening, do the following:
1. Connect the controller solid well with the power supply before turning on the power.
2. Make sure that the power supply has sufficient output current. It is suggested that the power supply can
supply 1.2 to 1.5 times the maximum current the controller requires.
3. When using a bench top power supply, set the current limit to >1.5 times higher than the maximum current
the controller requires.
ORDERING INFORMATION
Part # Description
ATLS500MA103D Controller in DIP package
ATLS500MA103S Controller in SMT package
ATLS500MA103-PD Controller with a pull-down resistor of 100K to the ground in SDN pin.
PRICES
Quantity 1 −9 10 −49 50 −199 200-499 ≥500
ATLS500MA103D
ATLS500MA103S
ATLS500MA103-PD
$75.0 $71.3 $67.5 $63.8 $60.0
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