Analog Technologies ALDD28V5A401 User manual

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
Figure 1. Physical Photo of ALDD28V5A401
FEATURES
Digital display for parameter setting and monitoring
Wide input voltage range: 10V ∼27V
Wide output voltage range: 0.1VVPS to 0.8VVPS (VVPS is
input voltage)
High current capability: 5A
High efficiency: ≥90%
(IOUT=5A @ VLDA=20V&VVPS=27V)
Wide modulation bandwidth: DC ∼10kHz
Compact size: 68.5×61.0×16.6 (mm)
Dual independent current set ports: LISH and LISL
Direct digital modulation control: PCN
Three control states: Operation, Standby and Shutdown
Low output current noise: < 15µAP-P@0.1Hz~10Hz
High current stability: < ±600µA@5A &‒20°C~80°C
Low output ripple voltage: < 15mVP-P@500kHz
Fully shielded
100 % Lead (Pb)-free and RoHS compliant
APPLICATIONS
Drive one or multiple laser diodes for DPSSL, EDFA, and
fiber lasers with low noise and high efficiency.
DESCRIPTION
This laser driver, ALDD28V5A401, is an electronic module
that has all the valuable and important features, but are often
difficult to achieve simultaneously such as: wide input and
output voltage range, high output current capability, high
efficiency, low output noise (but it has an output 6mVp-p
ripple voltage at 500kHz), wide modulation bandwidth, and
small size. The wide output voltage range, 0.1VVPS ~
0.8VVPS, allows driving one or multiple serial laser diodes at
the same time, for up to 5A of well controlled current at high
efficiency. The extremely low noise between DC ~ 10kHz
and low DC current drift make it ideal for driving diode
pumped single mode laser diodes to achieve mode-hop-free
and narrow optical wavelength drift, thus, long coherent
length.
Because of the high efficiency, the laser driver generates a
small amount of heat, thus, no heat sink is necessary for
normal operation. The fully shielded case blocks all the
incoming and outgoing EMIs (Electro-Magnet
Interferences). Therefore, this laser will not interfere other
surrounding electronics, nor will other electronics interfere
with it. The small package saves valuable PCB space in laser
systems. Figure 1 shows the photo of the ALDD28V5A401.
The actual laser current and laser driver temperature are
monitored by dedicated ports. In case the laser driver
temperature exceeds the limit of 80°C, the laser driver will
shut down the output stage by itself and force the laser drive
into Standby Mode. There is a loop good indication output
to tell if the laser driver is working properly.
The laser driver has three states: Operation, Standby and
Shutdown. Under Standby mode, all the laser driver
components works except the output stage, see Figure 4.
Under Shutdown mode, all the components of the laser
driver stops working and the power supply current is
reduced to < 3µA.
This laser driver generates a high accuracy high stability low
noise, 15mVP-P, < 2.5mVRMS, < 8ppm/°C, 4.096V<±2mV,
voltage reference output which can be used for setting the
output current and also be used as the reference voltage for
the ADCs (Analog to Digital Converters)and/or DACs
(Digital to Analog Converters).
The ALDD28V5A401 uses a constant frequency high
efficiency PWM output stage.
Warning: Both the surface mount and the through
hole types of packages can only be soldered manually on
the board by a solder iron of < 310°C (590°F), do not use
a reflow oven to solder this laser driver.
For noise sensitive applications, please be aware that this
laser driver has very low noise between DC to 10kHz, but a
little high ripple output voltage, sine-wave, 15mVP-P, at the
switching frequency, 500kHz.

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
Figure 2. Pin Names and Locations
Figure 2 is the top view of the ALDD28V15A401, which
also shows the pin names and locations. Its thickness is
17mm. The pin functions and specifications are described in
Table 1 below. Note that the metal case is internally
connected to ground.
Table 1.Pin Function Descriptions
Pin
# Name Type Description
1 LIO Analog Output
Laser Current Output indication. 0.1V to 4.096V indicates the laser current being from 0 to
5A linearly.
2 LIS Analog Input
Laser current low value setting voltage. There is a 10MΩinput resistor tied to GND. Setting
it from 0.1V to 4.096V will set the laser lower current from 0 to 5A linearly. The laser driver
will output the current set by this pin. The input bias current of this pin is < 0.1μA.
3 4VR Analog Output
Voltage Reference 4.096V output. It can source and sink up to 10mA output current, with a
very low 5μVP-P noise between 0.1 to 10Hz and < 6ppm/°C stability. Under Standby Mode,
this pin is still working.
4 GND Signal Ground
Signal Ground pin. Connect ADC and DAC grounds to here. When using POTs
(potentiometer) to set the output currents, connect the ground terminal of the POTs to here.
5 EN
Analog/Digital
Input
Standby and Shutdown Control. This pin has three states: between 0V ∼0.3V, it shuts down
the entire laser driver; between 0.5V ∼1.2V, it sets the laser driver to standby mode; between
1.5V ∼28V, it sets the laser driver to operation mode. The input current on this pin is < 2µA.
6 LPGD Digital Output
Loop Good indication. When the laser driver's output current equals the set-point current
value, and there is no short nor open circuit at the output, this pin is pulled up high by an
internal 3kΩresistor to an internal 5V power supply as shown in Figure 3; when the output
current is not equal to the set-point current, such as there is an open circuit at the output, or
the load has too high a resistance that even the output voltage reaches the power supply
voltage, the output current is still lower than the set-point value, this pin is pulled low by an
open drain MOSFET of which Rdson < 500Ω. When outputting the low value, the sinking
capability is < 0.5V at 1mA.
7 LDA Analog Output
Laser Diode Anode. Connect it to the laser diode anode terminal. The maximum current of
this pin can go up to 5A. When doing layout, do not use a thin and long PCB track, otherwise,
the inductance might be too high, and oscillation may occur.
8 LDC Analog Output
Laser Diode Cathode. Connect it to the laser diode cathode terminal. The current on this pin
can go up to 5A. Use thick and short PCB track for this pin to minimize the inductance to
avoid oscillation or ringing. This pin has a low voltage potential, when the output current is
5A, the potential is 30mV above PGND.
9 PGND Power Ground
Power ground pin. Connect this pin directly to power supply return path line, 0V. The
maximum current on this pin can go up to 5A.
10 VPS Power Input
Power supply voltage. The driver works from VVPS = 12V ~27V. The maximum current can
go up to 5A.

1161 Ringwood Ct, #110, San Jose, CA 95131, U. S. A. Tel.: [phone], Fax: [phone] www.analogtechnologies.com
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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
SPECIFICATIONS
Table 3. Characteristics (TAMBIENT= 25°C)
Parameter Value Unit
Power efficiency
IOUT =5A, VLDA =20V & VVPS = 27V. 90 %
Maximum output current 5 A
Low frequency output current noise,
peak-to-peak value, 0.1Hz to 10Hz, <15 µAP-P
Stability @ 5A &−20°C ∼80°C <±0.01 %
<±650 µA
Laser current control signal at LIS 0.1~4.096 V
LIS control accuracy ±0.1 %
Laser current indication signal at LIO 0.1~4.096 V
LIO indication accuracy ±0.2 %
Reference output voltage 4.096±0.008 V
Output voltage range at LDA 0.1VVPS to 0.8VVPS V
Output voltage at LDC 0 V
Power supply voltage range 10 ~27 V
Maximum power supply voltage 28 V
Start-up time upon releasing the SBDN pin above 2.6V 20 ms
Shutdown time upon pulling the SBDN pin down 20 µs
Standby current 8 mA
Shutdown current <2 µA
Operating case temperature −40 ~ 110 °C
Operating ambient temperature −40 ~ 85 °C

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 4
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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
Figure 3. Internal Block Diagram of ALDD28V5A401
OPERATION PRINCIPLE
The block diagram of the driver is shown in Figure 3.The
signal from pin 2, EN, is sent to a level detector circuit. As
shown in Figure 4, upon detecting signal level between 0V to
0.3V, the shutdown output is activated. It shuts down the
whole laser driver and drives the laser driver into shutdown
Mode. Upon detecting the level to be between 0.5 and 1.2V,
the standby signal is activated, it puts the controller into
Standby Mode. When the signal is between 1.5V and above,
the controller is driven into Operation Mode.
Figure 4. Input Control
There is a temperature protection circuit, upon detecting the
temperature to be >80°C, it will force the laser driver into
Standby Mode. The laser driver reinitiates the power up
sequence when the junction temperature drops below 80°C.
The voltage reference circuit provides internal voltage reference

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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
for the driver, its output is taken out after a noise removal
circuit at 4VR port, pin 4.
LIS pin set the output current without any offset voltage. The
relationship between the voltage and the output current is:
IOUT (A) = VLIS (V)/4.096 (V)×5 (A);
VLIS (V) = IOUT (A)/5 (A)×4.096 (V),
Where IOUT is the output current of the laser driver, VLIS
represents the voltage on the LIS, in volt.
The LIO port, pin 6, outputs an analog voltage that is
proportional to the actual output current. When the output
current is 0A, the LIO voltage is 0V; when output current is
5A, the LIO voltage is 4.096V. The relationship is:
VLIO (V) = IOUT (A)/5(A)×4.096 (V);
IOUT (A) = VLISL (V) /4.096(V)×5 (A);
VLIO is the voltage on the LIO pin.
The output stage is designed to achieve low noise, high
efficiency, and relatively high modulation speed. It has an over
current protection circuit. There is a soft start circuit which
increases the output current slowly at the start up time and shuts
down the current quickly.
The LPGD pin indicates the control loop status. When this pin
goes high, >2V, the control loop is working properly, i.e., the
output current equals to the desired value, VLIS = VLIO; when this
pin goes low, <0.3V, the laser driver is not working properly,
there might be a short or open circuit at the output, or the laser
driver is protected by the over temperature protection circuit.
APPLICATION INFORMATION
Figure 5. Stand-Alone Application Schematic

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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
Figure 6. Micro-Controller Based Application Schematic
Figure 6 shows a micro-controller based application
schematic.
Table 4 shows the relationship between Digital D1, D2, and
laser driver state. Refer to Figure 6.
Table 4.
Digital
Output
D1
Digital
Output
D2
Laser
Driver
State
0 0 Shutdown
0 1 Standby
1 0 Note
1 1 Operation
Note: For the input state D1=1 and D2=0, the controller's
state is depending on the output voltage at EN pin:
Where, VDis the logic1 output voltage for D1 & D2 signals.
Digital signal V1 and V2 controls the laser driver into
Shutdown, Standby or Operation mode. The starting up time
delay is about 20mS and the shut down time is about 20µS.
It is worth mentioning that to achieve high speed and low
distortion digital modulation, one can use the LIS pin to set a
current that is a little lower than the threshold current of the laser
diode to turn off the laser beam, such as half of its value. Use the
LIS pin to set the laser current when the laser diode is turned on.
In this way, the laser beam is turned on and off, while the driver
control loop is always kept on, so that the output stage is always
under control, no distortion is caused by turning on/off the
output stage.
When LPGD pin is high, > 2V, the laser diode control loop is
working properly. When LPGD pin is low, <0.3V, the laser
diode control loop is not working properly, there might be a
short or open circuit at the laser diode, or the laser driver is put
into Standby or Shutdown mode.
The LPGD pin can also be connected to a digital input pin of a
micro-driver, when software/firmware is utilized in the system.
The equivalent circuit of this pin is a 3kΩresistor pulling it up
to 5V rail and an open drain FET, 500Ω, pulling it down to the
ground. The pull-up current can be increased by connecting an
external pull-up resistor between LPGD and VPS. Tie this added
additional pull up resistor to a 3.3V or 5V power supply if they
are available. Make sure that the pull up current is not too high,
otherwise, the internal open drain FET cannot pull-down the
LPGD pin low enough to turn off the LED.
The laser diodes are connected between LDA and LDC pins. It
is worth mentioning that the power supply return terminal

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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
should be connected to the pin 9, PGND.
Minimizing the Output Noise
The laser driver has extremely low output noise; care must
be taken in using this laser driver to achieve this lower noise
performance. One of the noise sources is the beating
frequency interference from other power mode electronics,
such as another laser driver, TEC (Thermo-Electric Cooler)
controller, or power supply. There are 2 ways to avoid the
frequency beating: set the switching frequencies of other
electronics to be far away from the switching frequency of
the laser driver, 500kHz.
The driver can be turned on and off by setting the SBDN pin
high and low respectively. It is recommended to turn the
driver on by this sequence:
To turn on: turn on the power by providing the power supply
voltage to the driver on VPS pin, turn on the driver by
releasing the SBDN pin.
To turn off: turn off the driver by lowering the voltage of
SDN pin, turn off the power by stopping the voltage supply
on the VPS pin.
When not controlled by the SBDN pin: leave it unconnected
and turn the driver on and off by the power supply.
Adjusting the Output Current
The output current is set by adjusting W1, which sets input
voltages of LISL and LISH, pin 6 and 7. See Figure 6. The
output current will be:
IOUT (A) = 1.221 ×VLIS
LIS can also be set by using a DAC to replace the W1 in
Figure 6. Make sure that the DAC has low output noise.
Monitoring the Output Current
The output current of the driver can be monitored by
measuring the voltage on the LIO pin. This feature is very
useful for a micro-driver based system where the ADC is
available and monitoring of the current in real time is
required. This pin provides a very low noise voltage signal
and is proportional to the output current:
IOUT (A) =1.221 ×VLIO (A).
For example, when the output signal is 4.096V, the output
current is 5A.
LIO can be used to drive an ADC directly, and also be
measured by a multi-meter.
First Time Power Up
Laser diode is a highly valuable asset yet, a delicate device.
Faults in connections and damages done to the driver during
soldering process may damage the laser diode permanently.
To protect the laser diode, it is highly recommend to use 3 to
18 regular diodes which is > 5A to form a “dummy laser”
and insert it in the place of the real laser diode, when
powering up the driver for the first time.
Use an oscilloscope to monitor the LDA voltage at times of
powering up and enabling the shutdown pin and powering
down the laser driver and turning off the shutdown pin, and
make sure that there is no over-shoot output voltage at the
LDA pin. At the same time, it uses an ammeter in series with
the dummy laser, to make sure that the output current is
correct. After thoroughly checking and making sure the
system is free of faults, disconnect the dummy laser diode
and connect the real laser diode in place. The driver output
voltage range for the laser is between 0 to VVPS (power
supply input voltage).

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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
WORKING PRINCIPLE
1. After the controller is powered on, turn the switch on the
lower right to “SB”, the display contents are as follows:
2. Press the “Set” button, enter the password, and then enter
the setup mode.
Press the “Set” button, the display contents are as follows:
Two digits stand for the password. When the last digit
flashes, use “↑” to change the number (0 ~ 9); press the “Set”
button to select which digit to be changed. When the first
digit flashes, use “↑” to change the number (0 ~ 9). The
default password is "99". Once you enter the correct
password, you can start setting up the controller.
3. After entering the correct password, press and hold the
“Set” button to enter the setup mode. The display contents
are as follows:
We can select internal control or external control by pressing
the “↑” button, then press the “Set” button to lock the
selection, or press and hold the “Set” button to enter the
internal control or external control current setting.
The current can be adjusted by pressing the “Set” button to
place the cursor. Use the "↑" button to adjust the current.
Or
After setting the current, press and hold the “Set” button to
save the setting and exit to the initial state.
Press “↑” button to switch between the connection state and
temperature state

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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
Or
After the setting is completed, turn the switch to “ON” and
the controller starts working.
Press and hold the “Help” button, the display contents are as
follows:
OUTLINE DIMENSIONS
Dimensions of the DIP package driver are shown in Figure 7.
Figure 7. Dimensions of the DIP Package Driver
It is highly recommended to lower the solder iron
temperature to 310°C (590°F) and solder the driver
manually, so that the internal contents of the driver would
not be affected.
After the soldering, it is also safe to check the laser driver’s
functionality by using the “dummy laser” before connecting
a real laser diode as mentioned previously on page 4.
NOTE: The power supplies may have over-shoot voltage
spikes when they are not connected well with the load or
when they recover from an over current protection state.
When that happens, it may exceed the maximum allowed
input voltage, 27V, of the controller and damage the
controller permanently. To avoid this from happening, do
the following:
1. Connect the controller 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.

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 10
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nalog Technologies ALDD28V5A401
Digital High Voltage Constant Current 5A Laser Driver
3. When using a bench top power supply, set the current
limit to >1.5 times higher than the maximum current the
controller requires.
Warning: Both the surface mount and the through
hole types of packages can only be soldered manually on
the board by a solder iron of < 310°C (590°F), do not use
a reflow oven to solder this laser driver.
ORDERING INFORMATION
Table 5. Part Number
Part Number Description
ALDD28V5A401D 5A constant current driver
Table 6. Unit Price
Quantity (pcs) 1 −4 5 −24 25 −99 ≥100
Unit Price $539 $519 $499 $479
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