Analog Technologies ATLS1A102 User manual

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
Copyrights 2000-2021, Analog Technologies, Inc. All Rights Reserved. Updated on 3/11/2021 Email: [email protected]/[email protected]m 1
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nalog Technologies ATLS1A102
Low Noise Constant Current Laser Driver
FEATURES
Ultra Low Noise: <10µAP-P @0.1Hz to 10Hz
High Current without Heat Sink: 1A
High Absolute Accuracy: <0.1%
High Stability: 10ppm/°C
Dual Modulation Ports: High/Low Speed
Low Drop Out Voltage: 1V
Complete Shielding
Compact Size
100 % lead (Pb)-free and RoHS compliant
DIP and SMT Package Available
APPLICATIONS
Driving diode lasers with low noise, including DPSSLs,
EDFAs, fiber lasers, diode laser modules, etc.
DESCRIPTION
The ATLS1A102 is an electronic module designed for
driving diode lasers with up to 1A low noise current. The
output voltage is 1.5V to 4V when powered by a 5V power
supply.
The ATLS1A102 has two input ports for modulating the
output current: one for low speed of up to 0.08Hz bandwidth
and the other high speed modulation of up to 300kHz. The
former is for CW (Continuous Wave) operation and the
latter is for modulated operation.
A high stability low noise 2.5V reference voltage is
provided internally for setting the output current. This
reference can also be as the voltage reference for external
ADCs (Analog to Digital Converters) and DACs (Digital to
Analog Converters), which might be used for monitoring
and/or setting the laser current.
The shut down pin can turn the controller electronically
without disconnecting the power supply.
There is an output port, LIO (pin 11), dedicated for
monitoring the laser current. It can be connected to an ADC
or a voltmeter.
The control loop is monitored in real time by an internal
circuit, to make sure that it works properly. The monitoring
result is sent to the LPGD node (pin 12). When this pin is
pulled up internally, it indicates that the loops works fine.
By default, the maximum output current is set to 1A. This
value can be altered by external circuit which is shown in
the application section.
The ATLS1A102 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.
Figure 1. Pin Names and Locations
The controller has 2 types of mounting packages: through hole
and surface mount. The latter saves PCB space the controller
takes. Figure 1 is the actual size top view of the ATLS1A102D,
which shows the pin names and locations. Its thickness is 5mm.
SPECIFICATIONS
Parameter Value Unit/Note
Maximum output current 1 A
Output current noise
(0.1Hz to 10Hz) <10 µAP-P
Low speed current set voltage
(on LISL pin) 0~2.5 V
High speed current set voltage
(on LISL pin) 0~2.5 V
Low speed modulation cut-off
frequency 0.08 Hz
High speed modulation cut-off
frequency 300 kHz
Power supply voltage range 4.5~5.5 V
Thermal resistance
60 (free
air)
30 (PCB
mount)
°C/W
Operating case temperature −25~85 °C
Rise times of small signal 1.5 µS
Fall times of small signal 1 µS
Rise times of large signal 1.5 µS
Fall times of large signal 1 µS
OPERATION PRINCIPLE
Figure 2 is the block diagram of the controller.
Figure 2. Block Diagram
19.4
LPGD
LIO
VPS
PGND
LDA
LDC
GND
2P5V
LISL
P5V
LISH
SDN 1
3
4
5
6
212
10
9
8
7
11
14.5
LDC
Laser
Diode
7
8
6
LDA
LISH
Linear
Mode
Driver
Low
Pass
Filter
Control
Unit
10
5
4
2
1
P5V
LISL
GND
SDN
100nF 100KΩ
VPS
Current
Sense
9PGND

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
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nalog Technologies ATLS1A102
Low Noise Constant Current Laser Driver
APPLICATIONS
Figure 3 shows a stand-alone application circuit.
power supply 0V
D2 LED
31
2
W1
100K
(Clock-wise) Power Supply 5V
S1 SPST
D1
Laser Diode
Shut Down Loop Good Indication
(Optional)
LISH
6
LPGD 12
VPS 10
LDC 7
PGND 9
GND
2
P5V
5
SYNC 11
LDA 8
2P5V
3
LISL
4
SDN
1ATLS1A102
Sync. Signal
Current Setting
Figure 3. A Typical Stand-alone Application Schematic
Output Noise
Since the controller uses a switch mode driver, there will be
some ripple noise at the switching frequency, 1MHz. The
voltage magnitude is about 30mV at this frequency.
For applications which cannot tolerate this noise, users can
choosing the same controller with the switch mode driver
disabled. The part number becomes ADLS1A102-D-L or
ADLS1A102-S-L.
The disadvantage to turn off the switch mode driver is that
the efficiency of the controller will be lowered, thus, the
controller’s temperature may rise to too high a value. The
power consumption of the controller will be calculated in
this way:
PDRIVER = IOUT × (VVPS – VLDA),
where IOUT is the output current;
VVPS is the power supply voltage;
VDRIVER is the voltage across the laser diode.
If the PDRIVER is >2W, heat sink might be needed.
When prefer not to use the heat sink, this is option: lowering
the controller power consumption by reducing the power
supply voltage VPS. Please make sure:
VVPS ≥VDRIVERMAX + 1.2V,
where VDRIVERMAX is the maximum possible laser diode
voltage.
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: turn on the power by providing the power supply
voltage to the controller, turn on the controller by releasing
the SDN pin.
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 3, S1 is the shut down switch. The internal equivalent
input circuit of SDN pin is a pull-up resistor of 100k being
connected to VPS. If not using a switch (S1) to control the
laser, leave the SDN pin unconnected. D1 is the laser diode,
which is float from the ground and the VPS, with its anode
connected to the LDA, pin 8, and cathode connected to the
LDC, pin 7. 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. When higher pull up current is needed for such as
driving an 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.
Setting the Output Current
The LPGD pin can also be connected to a digital input pin of a
micro-controller, when software/firmware is utilized in the
system.
The output current is set by adjusting W1, which sets input
voltages of LISL, pin 4. The output current will be:
IOUT (A) = VLISL(V)/2.5 (V).
LISL should never be left float. Otherwise, the output current
will go too high a value that the laser might be damaged.
The LISL pin allows modulating the output current at a speed
of up to 0.08Hz. This low speed port filters out high frequency
noise, if any, in the input signal applied to this pin.
In addition to using the LPGD pin for monitoring the working
status of the controller, the output current can be monitored
directly by measuring the voltage of LIS pin when LPGD (loop
good) pin is high,. The equation is:
IOUT (A) = VLIS (V)/2.5 (V)
For example, when seeing LIS = 2.5V, the output current is
2.5V/2.5V = 1A.
Figure 4 shows an application where ATLS1A102 is interfaced
with a micro-controller.
LIO ADC
10
K

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
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nalog Technologies ATLS1A102
Low Noise Constant Current Laser Driver
power supply 0V
Power Supply 5V
D1
Laser Diode
(Optional)
LISH
6
LPGD 12
VPS 10
LDC 7
PGND 9
GND
2
P5V
5
SYNC 11
LDA 8
2P5V
3
LISL
4
SDN
1
Sync. Signal
DAC
MC MC
Figure 4. A Typical Micro-processor-based Application
In this circuit, the input current can be set by a DAC (Digital
to Analog Converter). By sensing the logic level of LPGD,
pin 12, the working status of the controller can be monitored
by a micro-controller (MC), when it is logic “1”, the loop is
good; “0”, the loop is at fault, which includes open circuit at
the laser diode connections, or short circuit from LDA to
ground, but excludes short circuit at the laser diode and
short circuit from LDC to ground. Shut down pin can also
be controlled by the micro-controller, setting it to logic “1”
turns on the controller, “0” turns it off. Please notice that
this pin comes with an internal pull up resistor of 100k, it
can be ORed (logic OR) by multiple digital ports of several
micro-controllers, with each of the port having an open-
drain output. The internal voltage reference output, 2P5V,
pin 3, can be used as the reference voltage for the ADCs and
the DACs.
The output current is set by adjusting W1, which sets input
voltages of LISL (Laser I (current) Set Low-speed), pin 4.
The output current will be:
IOUT (A) = VLISL (V)/2.5 (V).
LISL should never be left float. Otherwise, the output
current will go too high a value that the laser might be
damaged.
The LISL pin allows modulating the output current at a
speed of up to 0.08Hz. This low speed port filters out high
frequency noise, if any, in the input signal applied to this pin.
In addition to using the LPGD pin for monitoring the
working status of the controller, the output current can be
monitored directly by measuring the voltage of LIS pin. The
equation is:
IOUT = VLIS (V)/2.5 (V).
For example, when seeing LIS = 2.5V, the output current is
2.5V/2.5V = 1A.
MODULATING OUTPUT CURRENT
When low speed current modulation is needed, connect
LISL pin to the modulation signal. As LISL changes from 0
to 2.5V, the output current changes from 0 to 1A linearly.
The rise and fall time achieved by modulating LISL is about
4 seconds and the equivalent bandwidth is about 0.1Hz. The
advantage of using LISL as the modulation signal input port is
that the output current noise will not increase. The
disadvantage is that the speed is not high.
The LISL pin can be set by a POT, DAC, or a PWM signal
directly from a micro-controller. Please notice that when using
a PWM signal for setting the current voltage LISL, a low pass
filter will not be needed, since there is an internal low pass
filter.
It is recommended not to set the LISL 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 LISL
pin voltage to 0V, the output voltage will warble between 0V
and 2.5V, cause some oscillation slightly.
When high speed current modulation is needed, feed the
modulation signal to LISH (no need to connect LISH to P5V
pin). As LISH change from 0 to 0.5V, the output current
changes from 0 to 1A linearly. The fall and rise time is about
1μS, and the full power bandwidth is about 300kHz. Using
LISH pin as the modulation signal input port results in high
speed modulation, however, the noise from the modulation
signal source will be converted into output current noise.
The switch can be any analog switch, but having low leakage
current.
OUTPUT CURRENT MONITORING
The output current can be monitored in real time by measuring
the voltage on the LIS pin. When LPGD (loop good) pin is
high,
IOUT = VLIS (V)/2.5 (V).
For example, when seeing the LIS pin has a voltage of 2.5V,
the output current = 2.5V/2.5V = 1A.
Use a high input impedance voltage meter or DAC to monitor
the output current, such as >5k. Otherwise, some error will be
introduced at the output current. When the impedance is 5k, the
current error caused at the output is about 0.01%.
Please be aware that adding capacitor on this pin will increase
the high frequency noise current. Therefore, when monitoring
the output current on this pin continuously, insert a resistor of
about >5k in series with the voltage meter or ADC. In this way,
there is no big capacitance added on the LDC pin.
Under no-fault operation conditions, the output voltage of LDC
is always the same as that of LISH.
POWER UP PROCEDURE
Laser diode is a vulnerable device. Special cautions must be
taken for turning on the controller. These are the
recommendations:
1. Hold the SDN pin to ground by a mechanical switch or an
electronic logic device when turning on the power on the
VPS pin and release the SDN pin to logic high after the
LIO ADC

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
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nalog Technologies ATLS1A102
Low Noise Constant Current Laser Driver
VPS voltage is stabilized to turn on the laser.
2. If choose not to control the SDN pin for turning on the
laser, leave the SDN pin unconnected. There is an
internal capacitor holding SDN pin to logic low. Now,
the laser can be turned on and off by using the VPS pin.
Controller Power Consumption
The power consumption of the controller can be calculated
by:
PDRIVER = IOUT ×(VVPS – VLDA),
where IOUT is the output current;
VPS is the power supply voltage;
VLDA is the voltage across the laser diode.
When the PDRIVER exceeds 1W, a heat sink might be needed.
The best way for arranging the heat sinking for the driver is as
follows: transferring the heat by sandwiching a piece of
thermal conductive pad between the top metal surface of the
laser driver and the internal metal surface of the final product
as shown in Figure 5.1 and 5.2 below. The recommended
thickness of the thermal conductive pad in Figure 5.1 is
1~4mm, and in Figure 5.2 is 0.5mm. ATI also provides a series
of thermal conductive pads, click here for more information.
Figure 5.1 Transferring Heat with Metal Enclosure
Figure 5.2 Transferring Heat with Heat Sink

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
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nalog Technologies ATLS1A102
Low Noise Constant Current Laser Driver
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 regular
diodes of >1A 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.
MECHANICAL DIMENSIONS AND MOUNTING
The ATLS1A102 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: ATLS1A102−D, and the latter is often called SMT
(Surface Mount Technology) or SMD (Surface Mount
Device) package and has a part number: ATLS1A102−S.
19.4
1
3
4
5
6
2 12
10
9
8
7
11
14.5
R1.5×4
2
R1.5×2
Top View Side View
End View
5.0
12
Pin size: 0.5×0.5 4.0
R1.5×2
Figure 6. Dimensions of the DIP Package Controller
19.4
1.5 ×14
1.0 ×12 0.8 ×2
12
14.5
2 ×14
R1.5 ×4
PCB Copper
without solder pad
PCB Hole
Orientation Mark Outline
Figure 7. Top Side PCB Foot-print for the DIP Package
3.0 ×14
1.5 ×14
PCB Copper
with solder pad
Figure 8. Top View of the Bottom Side PCB Foot-print
Top View Side View
End View
5.6
16.8
Pin size: 0.5×0.5
R1.5×2
R1.5×4
19.4
14.5
1
3
4
5
6
212
10
9
8
7
11
1.15
2
R1.5×2
11.5
5.0
Figure 9. Dimensions of the SMT Package Controller
Figure 10 shows the foot print which is seen from the top side
of the PCB, therefore, it is a “see through” view.
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.

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
Copyrights 2000-2021, Analog Technologies, Inc. All Rights Reserved. Updated on 3/11/2021 Email: [email protected]/[email protected] 6
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nalog Technologies ATLS1A102
Low Noise Constant Current Laser Driver
NOTE: We don’t recommend this for new design.
ORDERING INFORMATION
Part # Description
ATLS1A102−D Controller in DIP package
ATLS1A102−S* Controller in SMT package*
Warning:The through hole 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.
PRICES
Quantity 1 −9 10 −49 50 −199 200 −499 ≥500
ATLS1A102−D
ATLS1A102−S $75 $71.3 $67.5 $63.8 $60.0
NOTICE
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being damaged by excessive abuse. Products found not meeting the specifications within one year from the date of sale can
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those pertaining to warranty, patent infringement, and limitation of liability. Testing and other quality control techniques are
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customers’ applications, adequate design and operating safeguards must be provided by the customers to minimize inherent
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