PICOLAS LDP-CWL 06-20 User manual

User Manual
LDP-CWL 06-20
LDP-CWL 12-20
- Preliminary Manual -
PicoLAS GmbH
Burgstr. 2
52146 Würselen
Germany
Phone: [phone]
Fax: [phone]
E-mail: [email protected]
Web:
www.picolas.de
Rev.2102

2
Table of Contents
Product overview...................................................................................................................... 3
How to use this manual........................................................................................................ 3
Dos and don’ts..........................................................................................................................4
Required laser diode pin out..............................................................................................8
Laser driver block diagram ..................................................................................................9
Description of the connectors of the LDP-CWL 06-20 / LDP-CWL 12-20.... 9
Modes and power dissipation..........................................................................................13
Frequency response..............................................................................................................17
Trigger delay............................................................................................................................18
Test load ....................................................................................................................................19
Power supply............................................................................................................................19
Crowbar......................................................................................................................................19
Current limiter .........................................................................................................................19
Mechanical dimensions .......................................................................................................20
Absolute maximum ratings (limits that can destroy the unit) ...........................20

3

4
How to use this Manual
Remark: The LDP-CWL 06-20 and LDP-CWL 12-20 described in this manual
are base plate cooled laser diode drivers. Improper cooling may cause an
internal overtemperature shutdown (max. 80 °C).
Base plate cooling: Depending on the final application and operation mode, this
unit may stay non-cooled or must be assembled onto a heat sink. Please refer to
section “Working Areas and Power Dissipation” for more details about the thermal
power losses during operation.
Before powering on your unit, read this manual thoroughly and make sure you
understood everything!
Please pay attention to all safety warnings.
If you have any doubt or suggestion, please do not hesitate to contact us!
Dos and Don’ts
Keep the cable connection between power supply and laser diode driver
and the connection between driver and laser diode as short as possible to
minimize the stray inductance.
Please set the laser diode driver only in the scheduled working area and only while
the power supply is turned off. Therefore please have a look at the section
“Description of the Connectors of the LDP-CWL 06-20 / LDP-CWL 12-20”.
Never disconnect or connect the load while the driver is operational, as it destroys
the driver and/or the connected load. Make sure that the control ground is
connected to the supply ground. Any unexpected current flow through the control
board may damage the driver.
Mount the driver on an appropriate heat sink.
Please be aware that there might be hot surfaces, be careful not to touch
them!

5
How to get started
Picture 1: LDP-CWL driver with connectors, jumper and measurement points
The basic settings such as output current limit setting for the crowbar
can be adjusted by the Potentiometer 1. The actual adjusted maximum
output current limit can be measured at MP1 (measurement point 1).
An additional waveform generator might be needed which has to be
connected to the input terminal. There is no AWG (arbitrary waveform
generator) included within the driver!
GND and LD- are internally directly connected!

6
Step What to do Check
1 Connect a dummy diode between
LD+ and LD-. Alternatively make a
short circuit there.
Refer to section “Test Load”.
Range of compliance voltage
0 V .. 20 V.
2 Set the working point of the LDP-
CWL to modulation mode (Mod.).*
There are three different working
points: CW mode, modulation
mode and manual mode.*
Refer to the section “Description
of the Connectors of the LDP-
CWL 06-20 / LDP-CWL 12-20”
3 Connect GND, Vcc on power
connector (power source yet
disabled).
Range of Vcc 15 V .. 48 V.
Minimum 10 V above compliance
voltage. Required max. current is
about 7 A - 13 A.
4 Connect waveform generator on
input terminal (no pulse before
power supply enabled, 0 V at current
set pin (10. pin of the pin header).
Refer to all sections referencing
input (connector #2).
5 Enable the power source. Crowbar LED is on (red)
6 Adjust max. current scaling of the
crow-bar.
Use the Set_Imax potentiometer 1
(refer to the picture 1 above) for
scaling of the crowbar. Scale:
3 A/V (example: 4 V at MP1 would
limit the output current to 12 A).
7 Disable (reset) the crowbar by
toggling the 7. pin of the pin header
(set low and then high 7. pin;
“Disable / reset crowbar”).
Crowbar LED is off (no light)
8 Feed a signal on the input terminal
(current set pin (10. pin). For
example 1 kHz sine wave with 1 V
amplitude and 0.5 V DC offset while
Make sure not to overload the
laser diode or the driver.
Range of input signal 0 V .. 4.8 V.
(0.4 V/A)

7
the LDP-CWL is in the “modulation
mode”.
9 Monitoring of the output current. On current monitor you can
measure a signal comparable
with the input signal. Use an
oscilloscope with a 1 MEG ohm
termination. Scale 3 A/V. (example:
4 V at current monitor read means 12 A
at the output)
10 Disable the input signal and turn off
the power source. Remove the test
diode or bypass and assemble the
final laser diode.
11 Turn the power supply for the Vcc
back on.
Range of Vcc 15 V .. 48 V.
Minimum
10 V above compliance voltage.
12 Feed a signal to the input terminal. Make sure not to overload the
laser diode!
*Important: Please refer to the position of the jumper as in the Picture 4, the
printing on the board may be different. However, it does not have any impact
on the functionality of the driver itself.
.
Required Laser Diode Pin Out
The LDP-CWL 06-20 / LDP-CWL 12-20 is designed for the direct connection of
almost any kind of laser diode with a maximum compliance voltage of 20 V.
The pitch of the LD- and LD+ connectors is 15.5 mm.

8
Laser Driver Block Diagram
Picture 2: Block diagram of the laser driver
Description of the Connectors of the LDP-CWL 06-20 /
LDP-CWL 12-20
Picture 3: Connectors of the laser driver

9
#1 and #2. Power Supply absolute maximum Ratings
Pin Allowed range Best
performance
Destroying limit
1 Vcc
(laser supply)
15 V .. 48 V 10 V above
compliance
49 V
2 (GND) GND GND
Connector Function Description
1 Power connector: Vcc Screw terminal M3
2 Power connector: GND for Vcc and
input signal
Screw terminal M3
3 Pin header See section “Connection
Pin header”
4 Jumper J1 Set the working area. See
section “Modes and
Power Dissipation”
5 Laser diode connector (anode) LD+
6 Laser diode connector (cathode) LD-

10
#3. Connection Pin header (for LDP-CWL 12-20)
Pin
number
Function
1 N.C.
2 +5 V
3 GND
4 V compliance
(output voltage)
5 GND
6 N.C.
7 Disable /
reset crowbar
(connect to GND to
disable/reset)
8 N.C.
9 Current monitor
output
(3 A/V, ± 5%))
(example: 4 V at current
monitor output
corresponds to 12 A at
the output)
10 Set output current
(0.4 V/A)
(example: 4.8 V
reference voltage
corresponds to 12 A at
the output)

11
Set Output Current:
The analog current setpoint signal is provided via pin #10. The output current
follows the input signal proportionally within the driver’s limitations (bandwidth,
max. current, rise time). The scaling of this pin is 0.4 V/A (example: 4.8 V reference
voltage corresponds to 12 A at the output).
Current Monitor Output:
The current monitor output has a scale of 3 A/V (± 5%) (example: 4 V at current
monitor output corresponds to 12 A at the output). To achieve the correct scaling
this pin has to be terminated with a high termination such as an oscilloscope and
1 MEG Ohm input impedance. Due to the scaling amplifier and the quiescent
current, current flows through the output from up to 150 mA, the current monitor
output has an offset of approximately 50 mV.
#4. Connection Jumper J1
Jumper connection Working area of the
LDP-CWL XX/20
Short circuit between
pin 5 and 6
Continuous wave mode
(CW)
Short circuit between
pin 3 and 4
Modulation mode
(Mod.)
Short circuit between
pin 2 and 1
Manual mode (Man.)
Security Advice: Please jumper only the scheduled pins and while the power supply is
turned off.

12
Picture 4: Jumper positions for different modes
With Jumper J1 it is possible to set the working area of the LDP-CWL. Please set
the working area while the power supply and the input signal of the LDP-CWL are
turned off. Furthermore, please only set the working area as represented in the
upper pictures.
Important: Please refer to the position of the jumper as in the Picture 4, the
printing on the board may be different. However, it does not have any impact on
the functionality of the driver itself.
#5 and #6. Laser Diode Connection
Many elements and parasitic “stray” components may affect the performance of
the LDP-CWL. The stray inductance of the load connected to the driver is very
important. “Load” means not only the diode itself but also the packaging (bond
wires!) and leads between the driver and the diode. However, PicoLAS has no
influence on these parts. Thus, all measurements have been performed into a short
instead of a laser diode.
Refer to the PicoLAS Application notes “Impedance of Diodes” and “LD-
Connections” to get more information about parasitic elements and their effect on
the pulse shape (https://picolas.de/downloads/).

13
Modes and Power Dissipation
Important: The names of the modes on the board may differ in earlier
versions of this curcuit. Please refer to this updated manual for the order and
the names of the modes.
To cover many different working areas of the LDP-CWL, the driver has the
possibility to change the internal working area for the most suitable operation.
The LDP-CWL can be set in three different working areas continuous wave mode
(CW), modulation mode (Mod.) and manual mode (Man.).
In every working area the driver achieves the best combination of a switching and
a linear regulator. This technique allows high energy consumption, great linearity
characteristics with a low output current ripple.
Mount the driver on an appropriate heat sink.
Please be aware that there might be hot surfaces, be careful not to
touch them!
Modes
In the continuous wave mode (CW) it is possible to set the LDP-CWL for
continuous signals with high efficiency. Independent of the load and according to
the output current, the driver has linear power consumption.
The following graph shows the typical power consumption of the LDP-CWL against
the output current.

14
0
5
10
15
20
25
30
0 2 4 6 8 10 12
I / A
Pd / W
In the modulation mode (Mod.) the LDP-CWL can modulate any periodic signals
(sine, triangular etc) according to its specifications e.g. bandwidth, linearity, output
current. The LDP-CWL provides a step response with rise times more than 10 µs at
an output current of 12 A in modulation mode. To achieve a higher bandwidth and
slew rate and to avoid distortion, please use the Manual Mode.
Picture 5: Blue: current monitor
Purple: output current set (pin #10 of pin header #3)

15
The graph below represents the power dissipation against the output current while
the LDP-CWL is used with a continuous wave signal in the modulation mode.
5
6
7
8
9
10
11
12
13
0 2 4 6 8 10 12 14 16 18 20
Vcompliance [V]
Power Dissipation [W/1A]
To estimate the power consumption of your system, you have to read the power
dissipation at the desired output current. Afterwards this value has to be multiplied
with the duty cycle.
Example:
Rectangle wave with a duty cycle of 20 %
 Desired output current = 5 A
 Desired compliance voltage = 10 V (Resulting Pd from the graph is 8 W/1A)
 Power dissipation = 8 W/1 A * 5 A *0.2 = 8 W
The manual mode (Man.) is appropriate for pulsed signals such square wave. In
this mode, LDP-CWL 12-20 can achieve rise times less than 4.8 µs at an output

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current of 12 A and LDP-CWL 06-20 can achieve rise times less than 4.8 µs at an
output current of 6 A.
With the potentiometer 2 (adjust Vdc_link, measurement point 2; refer to section
“How to get started”), the DC link voltage can be adjusted (refer to section “Laser
Driver Block Diagram”) to increase the collector emitter voltage of the transistor of
the linear regulator, to achieve higher bandwidths for waveforms such as pulsed or
rectangle waves.
DC link voltage has to be less than Vcc-10 V and more than 5.5 V
+ Vcompliance to achieve higher bandwidths.
Frequency Response
The following graph demonstrates the 3dB bandwidth for increasing output current
values of the LDP-CWL 12-20 in manual modus. The following measurement
results are made on a dummy diode with a compliance voltage of 12 V.
0,00
2,00
4,00
6,00
8,00
10,00
12,00
1,00 10,00 100,00 1000,00
f [kHz]
Iout [A]

17
Trigger Delay
The delay between the triggering signal and the load-current is typically
td=2.2 µs.
Picture 6: Trigger delay

18
Test Load
For the first test, an appropriate test load may be assembled instead of the laser
diode. This test load can either be a short circuit or a dummy diode load. Please
connect the test load only between anode and cathode (LD+ and LD-) and prevent
contacts to any other parts of the circuit.
Power Supply
The power supply must be able to cover the output power plus the internal power
losses (please see next section).
Crowbar
After supplying the LDP-CWL XX-20 with appropriate voltage source, the red LED
of the crowbar will be on, indicating that the crowbar is active. At this point there
can be no output current flowing. To activate the output current so that it can the
output current set pin (10. pin of the pin header) crowbar has to be toggled (set
low and then high) (7. pin of the pin header).
For inherent protection, the LDP-CWL automatically shuts down itself if an error
occurs. Firstly if temperature rises above 80 °C, secondly if no load is connected
and thirdly if the output current is higher than the set current. This condition is
latched. To re-enable the LDP-CW the ENABLE pin must be toggled (set low and
then high).
Current Limiter
The LDP-CWL XX-20 is equipped with a current limiter. This can be used to
configure a maximum valid current set point which cannot be overstepped. To
configure the maximum output current use the measuring point 1 (MP1) on the
PCB (See Picture 1). The scaling of the current limiter is 3 A/V and can be set by
the potentiometer. If you want to disable the current limiter then set the voltage
to 3 V. Watch out because you might damage or destroy your load.

19
Mechanical Dimensions
Picture 7: Mechanical dimensions
Absolute maximum Ratings (limits that can destroy the unit)
 Vcc limit: The input voltage is in the range of 15 V .. 48 V but at least 10 V
above compliance voltage
 Output current: 6.0 A (LDP-CWL 06-20) / 12.0 A (LDP-CWL 12-20)
 Operating temperature range: 0 °C .. +55 °C
 Operating temperature range for best performance: +10 °C .. +35 °C
storage temperature range: -20 °C .. +70 °C