THORLABS MLDEVAL User manual
Miniature Laser Driver
Evaluation Board
MLDEVAL
User Manual
2021
Version:
Date: 1.2
19-Feb-2021
Copyright © 2021 Thorlabs
Foreword
Contents
1 General Information 1
11.1 Safety 21.2 Ordering Codes and Accessories 21.3 Parts List
2 Operating Elements 3
42.1 Power Supply Connection 42.2 Laser Current Limitation 42.3 Laser Current Monitoring 42.4 CP Feedback Loop Compensation
3 Preparation 5
4 Operating a MLD203PxE Module (CP) 6
74.1 External Power Control
5 Operating a MLD203CxxE Module (CC) 8
95.1 External Current Control
6 Appendix 10
106.1 Technical Data 116.2 Schematic Diagrams 146.3 Dimensions 196.4 Documentation Reference 206.5 Tutorial 216.6 Warranty 216.7 Copyright and Exclusion of Reliability 226.8 Thorlabs Worldwide Contacts
© 2021 Thorlabs
We aim to develop and produce the best solution for your application
in the field of optical measurement technique. To help us to live up to
your expectations and constantly improve our products we need
your ideas and suggestions. Therefore, please let us know about
possible criticism or ideas. We and our international partners are
looking forward to hearing from you.
Thorlabs GmbH
Warning
Sections marked by this symbol explain dangers that might result in
personal injury or death. Always read the associated information
carefully, before performing the indicated procedure.
Please read this advice carefully!
This manual also contains "NOTES" and "HINTS" written in this form.
Attention
Paragraphs preceded by this symbol explain hazards that could
damage the instrument and the connected equipment or may cause
loss of data.
Note
© 2021 Thorlabs
1 General Information
1
1 General Information
The MLDEVAL is designed for evaluation of a module of the MLD203 Miniature Laser Driver
Series to adapt the MLD203 Series external circuitry a selected by the user laser diode. In the
section Documentation Reference the links to the MLD203 Series Data Sheets and the com-
patibility to common laser diode pin configurations can be found.
The MLDEVAL board has a socket to accommodate an adapter PCB with mounted MLD203
laser diode controller. There are available four adapters (see section Ordering Codes and Ac-
cessories ) that need to be ordered separately.
The laser diode can be connected in different ways:
There is a screw terminal to connect the laser diode directly, using any individual wiring or a
Thorlabs SR9x Series ESD Protection and Strain Relief Cable.
A 9-pin DSUB connector allows the connection of the laser diode using a Thorlabs SR9x-DB9
Series cable with the appropriate DSUB plug.
The MLDEVAL is powered either via USB2.0 (USB charger) or from an external power supply.
A reverse voltage protection circuit observes both power inputs and enables the external power
supply if both are connected.
ESD Notice
The MLDEVAL is power input has an isolated ground potential. For this reason, the used power
supply must have a galvanic isolation between its GND output and the neutral / protective con-
ductor of the power line. Four rubber feet on the PCB's bottom provide an electrical isolation to
the work bench.
1.1 Safety
Attention
All statements regarding safety of operation and technical data in this user guide will
only apply when the unit is operated correctly as it was designed for.
Prior to apply power to the MLDEVAL, make sure that the switch SW1 (LASER ON/OFF)
(see section Operating Elements on page ) is switched off.
The MLDEVAL must not be operated in explosion endangered environments!
Only with written consent from Thorlabs may changes to single components be made or
components not supplied by Thorlabs be used.
Follow the common recommendations for handling of ESD sensitive devices when in-
stalling a MLD203x Miniature Laser Driver and the appropriate laser diode to the
MLDEVAL.
Warning
Laser emission is dangerous to human eye. Do not stare into the emitting aperture, wear
protective glasses and observe the safety instructions supplied with the laser diode.
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3
© 2021 Thorlabs2
MLDEVAL
1.2 Ordering Codes and Accessories
Ordering Code
Description
MLDEVAL
Evaluation Board for MLD203 Miniatur Laser Driver Series
Optional Accessories
·MLD203P1E Adapter PCB with MLD203P1
·MLD203P2E Adapter PCB with MLD203P2
·MLD203CHBE Adapter PCB with MLD203CHB
·MLD203CLNE Adapter PCB with MLD203CLN
·USB-AB-72 USB A to Mini B Cable, length 72" (1.83 m)
·SR9x ESD Protection and Strain Relief Cables
·SR9x-DB9 ESD Protection and Strain Relief Cables with DB9 connector
Note
Adapter PCBs are not included with the MLDEVAL. They need to be ordered separately!
Please visit https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2710 for closer in-
formation about SR9x and SR9x-DB9 cables with respect to laser diode pin codes.
1.3 Parts List
Inspect the shipping container for damage.
If the shipping container seems to be damaged, keep it until you have inspected the contents
and you have inspected the MLDEVAL mechanically and electrically.
Verify that you have received the following items within the package:
1. MLDEVAL Evaluation Board
2. Insert with important product information
© 2021 Thorlabs
2 Operating Elements
3
2 Operating Elements
1
USB power supply terminal 5 V DC
2
External power supply terminal 5 V DC ± 5 %
3
J8 and J9 - Sockets for adapter PCB. The white triangle marks pin 1 of the adapter
4
SW4.1 to SW4.4 mode switches
5
Constant Power Gain Monitor. Accessible only when no adapter is installed
6
SW2 and SW3 Laser diode pin code selection for DB9 output connector
7
DB9 output connector
8
Screw terminal for laser diode connection
9
SW1 LASER ON/OFF: Power on/off
10
P2 Pset / Iset Potentiometer to set power (MLD203P1 / MLD203P2) or current
(MLD203CHB / MLD203CLN)
11
Mod. In SMA connector for external control voltage input
12
P1 TIA Gain Potentiometer to set the TIA gain (monitor current limit) - only
MLD203P1 / MLD203P2
13
J6 Mon. Current Connector to monitor the laser diode current.
Conversion coefficient 1 V/A
© 2021 Thorlabs4
MLDEVAL
2.1 Power Supply Connection
The MLDEVAL comprises an integrated active circuit that automatically switches between the
two available power sources. In the case that both the USB and the external power supply is
connected to the MLDEVAL, it will automatically use the external power supply. The protection
circuit features also a reverse voltage protection and a reverse current blocking.
2.2 Laser Current Limitation
In some specific applications it might be useful to to limit the laser injection current, for ex-
ample, for very low power laser diodes, particularly when they will be operated in CC mode.
This limitation is achieved by inserting a resistor R1 next to the jumper JP1 into the output cur-
rent path. Its resistance is calculated to
with UC- compliance voltage of the used MLD203xxxE module. The compliance voltage
ranges from 3 V to 4 V, depending on the operation point. The minimum operating current
should be measured for each application separately.
ULD - forward voltage of the laser diode at its maximum allowed injection current ILD,MAX
Solder an SMD resistor of the calculated value, with 1206 or 0805 footprint to the position R1.
Remove the connected in parallel jumper JP1 to enable the current limitation.
2.3 Laser Current Monitoring
The laser diode current can be monitored at the J6 Mon. Current Connector (13) by measuring
the voltage at this connector. The conversion coefficient is 1 V/A, so the current is calculated by
2.4 CP Feedback Loop Compensation
Note
Only for MLD203P1E and MLD203P2E !
The control loop of the MLD203P1 and MLD203P2 are optimized for standard TO Can laser di-
odes. When using different lasers with different photodiodes it might become necessary to
compensate the parasitic capacitance of the used photodiode. The parasitic resistance and
parallel capacitance of the used photodiode results in a time constant. To compensate the con-
trol loop we recommend to match the time constants of the photodiode with the time constant
of the used module.
This can be done by adding a SMD capacitor ( Footprint 0603 or 0805) to position C4 located
on the MLDEVAL PCB between J7 and J9.
© 2021 Thorlabs
3 Preparation
5
3 Preparation
Prior to start evaluation:
·Compare the pinning of your laser diode, that can be found on its data sheet, with the stand-
ard pin codes (see page ) and find the matching pin code.
·Choose the desired operating mode - Constant Power (CP) or Constant Current (CC)
Note If you want to operate your laser in CP mode, it must have a built-in monitor diode.
Thus, the pin codes E, G and H are not supported by CP modules as these laser diodes
have no monitor diode.
·Select the evaluation adapter PCB:
oFor CP mode, the selection of the appropriate adapter PCB depends on the pin code of
your laser - MLD203P1E (pin codes A, B or F) or MLD203P2E (pin codes C or D). then
continue with Operating a MLD203PxE Module (CP) on page .
oFor CC mode, select the appropriate adapter PCB depending on your preferences regard-
ing low noise (MLD203CLNE) or high modulation bandwidth (MLD203CHBE). All pin
codes are supported. Then continue with Operating a MLD203CxxE Module (CC) on
page .
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© 2021 Thorlabs6
MLDEVAL
4 Operating a MLD203PxE Module (CP)
1. Define from the data sheet of your laser the monitor current IPD,MAX, that is equivalent to the
maximum optical output power.
2. Calculate the resistance RCOMP:
For MLD203P1E PCB adapter
For MLD203P2E PCB adapter
3. Set the mode switches SW4.1 to 4.2 (4):
SW4.1
Pset / Iset
ON
SW4.2
Mod. In
OFF
SW4.3
Comp
ON
SW4.4
Comp
ON
4. Connect an ohmmeter to the constant power monitor connector pins J7 (5) and adjust the
potentiometer P1 (12) to the calculated above value RCOMP. Disconnect the ohmmeter from
J7.
5. Set the potentiometer P2 (10) to the left stop by turning it counter-clockwise. This position
refers to the minimum output power.
6. Insert the MLD203P1E (MLD203P2E) into the sockets J8/J9 (3). Make sure that the white
triangle matches with pin 1 of the adapter PCB.
7. Connect the laser diode
·Free wiring: Connect the laser diode to the screw terminal (8) to Anode and Cathode,
accordingly. Connect the monitor diode lead to PD.
·Strain relief cable of SR9x Series: Use the cable version that matches the pin code of
your laser:
SR9A - pin codes A and E
SR9B - pin codes B and H
SR9C - pin code C
SR9D - pin code D
SR9F - pin codes F and G
Connect the red, blue and white wires to Anode, Cathode and PD of the screw terminal
(8) in accordance with the delivered with the SR9x cable documentation.
·Strain relief cable of the SR9x-DB9 Series: Use the cable version that matches the pin
code of your laser:
SR9A-DB9 - pin codes A and E
SR9B-DB9 - pin codes B and H
SR9C-DB9 - pin code C
SR9D-DB9 - pin code D
SR9F-DB9 - pin codes F and G
Set the pin code selector switches SW2 and SW3 (6) to match the pin code of your laser.
Connect the DSUB plug to the DB9 output connector (7).
8. Make sure that SW1 (9) is set to off.
9. Connect the power supply (external 5 V DC via or a USB power) to the MLDEVAL.
© 2021 Thorlabs
4 Operating a MLD203PxE Module (CP)
7
10. Set SW1 (9) to ON. The green LED1 next to SW1 lights up.
11. Turn the potentiometer P2 clockwise in order to increase optical output power. This way,
the control voltage at the PSET input of the MLD203PxE module can be changed between 0
and the internal reference voltage VREF (2.5 V DC). At the right stop of P2, the laser output
power will be equal to the maximum that you have defined (see topic 1 of this section).
4.1 External Power Control
As described in the previous section, the potentiometer P2 is used for adjusting the optical out-
put power of the MLD203P1E or MLD203P2E module. Using P2, the control voltage at the PSET
input of the MLD203PxE module can be changed between 0 and the internal reference voltage
VREF (2.5 V DC).
The same can be achieved from an external voltage source.
Attention
The external voltage must not exceed the range from 0 to +2.5 V DC in order to avoid damage
to the MLDEVAL and the MLD203PxE!
1. Prepare the MLDEVAL as described on page in steps 1 and 2.
2. Set the mode switches SW4.1 to 4.2 (4):
SW4.1
Pset / Iset
OFF
SW4.2
Mod. In
ON
SW4.3
Comp
ON
SW4.4
Comp
ON
3. Connect an ohmmeter to the constant power monitor connector pins J7 (5) and adjust the
potentiometer P1 (12) to the calculated above value RCOMP. Disconnect the ohmmeter from
J7.
4. Connect the external voltage source via the Mod. In SMA connector (11). Set the output
voltage of the external source to 0.
5. Insert the MLD203P1E (MLD203P2E) into the sockets J8/J9 (3). Make sure that the white
triangle matches with pin 1 of the adapter PCB.
6. Connect the laser diode as described in topic 7 on page .
7. Make sure that SW1 (9) is set to off.
8. Connect the power supply (external 5 V DC via or a USB power) to the MLDEVAL.
9. Set SW1 (9) to ON. The green LED1 next to SW1 lights up.
10. Now, the external control voltage can be changed within the range from 0 to +2.5 V.
Note
The external control voltage can be used for modulation. However, the modulation frequency is
limited by the feedback loop of the monitor current control. For a laser current modulation, the
constant current MLD203Cxx Miniature Driver Series is better suited.
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© 2021 Thorlabs8
MLDEVAL
5 Operating a MLD203CxxE Module (CC)
1. Set the mode switches SW4.1 to 4.2 (4):
SW4.1
Pset / Iset
ON
SW4.2
Mod. In
OFF
SW4.3
Comp
OFF
SW4.4
Comp
OFF
2. Set the potentiometer P2 (10) to the left stop by turning it counter-clockwise. This position
refers to the minimum laser current.
3. Insert the MLD203CHBE (MLD203CLNE) into the sockets J8/J9 (3). Make sure that the
white triangle matches with pin 1 of the adapter PCB.
4. Connect the laser diode
·Free wiring: Connect the laser diode to the screw terminal (8) to Anode and Cathode,
accordingly.
·Strain relief cable of SR9x Series - you can use any of the cables:
SR9A
SR9B
SR9C
SR9D
SR9F
Connect the blue and white wires to Anode and Cathode of the screw terminal (8) in
accordance with the delivered with the SR9x cable documentation.
·Strain relief cable of the SR9x-DB9 Series - you can use any of the cables:
SR9A-DB9 - pin codes A and E
SR9B-DB9 - pin codes B and H
SR9C-DB9 - pin code C
SR9D-DB9 - pin code D
SR9F-DB9 - pin codes F and G
Set the pin code selector switches SW2 and SW3 (6) to match the pin code of your laser.
Connect the DSUB plug to the DB9 output connector (7)
5. Make sure that SW1 (9) is set to off.
6. Connect the power supply (external 5 V DC via or a USB power) to the MLDEVAL.
7. The laser diode current can be monitored at the J6 Mon. Current Connector (13) by meas-
uring the voltage at this connector. The conversion coefficient is 1 V/A, so the current is cal-
culated by
8. Set SW1 (9) to ON. The green LED1 next to SW1 lights up.
9. Turn the potentiometer P2 clockwise in order to increase the laser current. This way, the
control voltage at the ISET input of the MLD203CxxE module can be changed between 0
and the internal reference voltage VREF (2.5 V DC).
Warning
Make sure you observe the laser current while turning the potentiometer P2! At its right stop the
laser current will reach the maximum value of 200 mA! In the case you need to limit the laser
© 2021 Thorlabs
5 Operating a MLD203CxxE Module (CC)
9
current to lower value, please see the recommendations given in section Laser Current Limita-
tion !
5.1 External Current Control
As described in the previous section, the potentiometer P2 is used for adjusting the laser cur-
rent of the MLD203CHBE or MLD203CLNE module. Using P2, the control voltage at the ISET in-
put of the MLD203CxxE module can be changed between 0 and the internal reference voltage
VREF (2.5 V DC).
The same can be achieved from an external voltage source.
Attention
The external voltage must not exceed the range from 0 to +2.5 V DC in order to avoid damage
to the MLDEVAL and the MLD203PxE!
1. Set the mode switches SW4.1 to 4.2 (4):
SW4.1
Pset / Iset
OFF
SW4.2
Mod. In
ON
SW4.3
Comp
OFF
SW4.4
Comp
OFF
2. Connect the external voltage source via the Mod. In SMA connector (11). Set the output
voltage of the external source to 0.
3. Insert the MLD203CHBE or MLD203CLNE into the sockets J8/J9 (3). Make sure that the
white triangle matches with pin 1 of the adapter PCB.
4. Connect the laser diode as described in topic 4 on page .
5. Make sure that SW1 (9) is set to off.
6. Connect the power supply (external 5 V DC via or a USB power) to the MLDEVAL.
7. The laser diode current can be monitored at the J6 Mon. Current Connector (13) by meas-
uring the voltage at this connector. The conversion coefficient is 1 V/A, so the current is cal-
culated by
8. Set SW1 (9) to ON. The green LED1 next to SW1 lights up.
9. Now, the external control voltage can be changed within the range from 0 to +2.5 V.
Warning
Make sure you observe the laser current while applying a modulation signal! At an input voltage
of 2.5 V (= offset voltage plus amplitude), the laser current will reach the maximum value of 200
mA! In the case you need to limit the laser current to lower value, please see the recommenda-
tions given in section Laser Current Limitation !
4
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4
© 2021 Thorlabs10
MLDEVAL
6 Appendix
6.1 Technical Data
Supply Voltage
5 V DC ±5 %
Operating Temperature Range 1)
0 - 40 °C
Storage Temperature Range
-40 to 70 °C
Dimensions (W x H x D)
105.8 mm × 56.0 mm × 14.1 mm
Weight
0.04 kg
1) non-condensing
All technical data are valid at 23 ± 5°C and 45 ± 15% rel. humidity (non condensing)
© 2021 Thorlabs
6 Appendix
11
6.2 Schematic Diagrams
For better readability in this manual, the schematic diagram is split in functional blocks.
MLD203xxxE interface (see Operating Elements on page , items 3, 4, 5, 10, 11, 12 and 13)
Screw terminal for laser diode connection (see Operating Elements on page , item 8)
3
3
© 2021 Thorlabs14
MLDEVAL
6.3 Dimensions
Dimensions MLDEVAL Board
© 2021 Thorlabs
6 Appendix
15
Dimensions MLD203P1E Module
© 2021 Thorlabs16
MLDEVAL
Dimensions MLD203P2E Module
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