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. 2001

2
Table of Contents
Product Overview..........................................................................................................3
How to use this Manual.................................................................................................4
Dos and Don’ts..............................................................................................................4
Required Laser Diode Pin Out.......................................................................................7
Laser Driver Block Diagram .........................................................................................7
Description of the Connectors of the LDP-CWL 06-20 / LDP-CWL 12-20................8
Working Areas and Power Dissipation .......................................................................11
Frequency Response....................................................................................................14
Trigger Delay...............................................................................................................15
Test Load.....................................................................................................................16
Power Supply...............................................................................................................16
Crowbar.......................................................................................................................16
Current Limiter............................................................................................................16
Mechanical Dimensions ..............................................................................................17
Absolute maximum Ratings (limits that can destroy the unit)....................................17

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.
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.
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
LDP-CWL driver with connectors, jumper and measurement points
The basic settings such as maximum current setting for the crow-bar can be
adjusted by the potentiometer. The actual adjusted maximum output current
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!

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. There are three different working
points: pulse mode, modulation mode
and cw 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 disabled). Range of Vcc 15 V .. 48 V. Minimum
10 V above compliance voltage.
Required max. current is about
6 A /12 A.
4 Connect waveform generator on input
terminal (no pulse before power supply
enabled).
Refer to all sections referencing input
(connector #2).
5 Enable the power source.
6 Adjust max. current scaling of the crow-
bar. Use the Set_Imax potentiometer 1 (refer to the picture above) for scaling
of the crowbar. Scale 0.3 V/A.
7 Feed a signal on the input terminal. For
example 1 kHz sine wave with 1 V
amplitude and 0.5 V DC offset while the
LDP-CWL is in the “pulse mode”.
Make sure not to overload the laser
diode or the driver.
Range of input signal 0 V .. 4.8 V.
8 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 0.3 V/A.
9 Disable the input signal and turn off the
power source. Remove the test diode or
bypass and assemble the final laser diode.
10 Turn the power supply for the Vcc back
on.
Range of Vcc 15 V .. 48 V. Minimum
10 V above compliance voltage.
11 Feed a signal to the input terminal. Make sure not to overload the laser
diode!

7
Required aser 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.
aser Driver Block Diagram
Block diagram of the laser driver

8
Description of the Connectors of the DP-CW 06-20 /
DP-CW 12-20
Connectors of the laser driver
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 “Working Areas and
Power Dissipation”
5 Laser diode connector (anode) LD+
6 Laser diode connector (cathode) LD-

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
#3. Connection Pin header
Pin
number Function
1 N.C.
2 +5 V
3 GND
4 V compliance
5 GND
6 N.C.
7 Disable /
reset crowbar
connect to GND
8 N.C.
9 Current monitor
10 Set output
current
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 .. 4.8 V/A.
Current Monitor Output:
The current monitor output has a scale of 0.33 V/A (± 5%). 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 100 mA, the current monitor output has an offset of
42 mV.

10
#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 Pulse mode (Pls.)
Short circuit between pin 2
and 1 Modulation mode (Mod.)
Security Advice: Please jumper only the scheduled pins and while the power supply is turned
off.
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.
#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 (bondwires!) 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 Appnotes “Impedance of Diodes” and “LD-Connections” to get
more information about parasitic elements and their effect on the pulse shape.

11
Working Areas and Power Dissipation
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 pulse mode (Puls.).
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!
In the continuous wave mode (cw mode) 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.
0
5
10
15
20
25
30
0 2 4 6 8 10 12
I / A
Pd / W

12
In the pulse mode the LDP-CWL can modulate any signals according to its specifications
e.g. bandwidth, linearity, output current. The LDP-CWL provides in this mode rise times
higher 9 µs at an output current of 12 A. To avoid distortion and achieve a higher slew rate
please use the Modulation Mode.
Blue: current monitor
Purple: output current set (pin #10 of pinheader #3)

13
The graph below represents the power dissipation against the output current while the
LDP-CWL is used with a continuous wave signal in the pulse mode.
4,5
5,5
6,5
7,5
8,5
9,5
10,5
11,5
12,5
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 modulation mode is appropriate for pulsed signals such as rectangles. In this mode,
LDP-CWL 12-20 can achieve rise times less than 9 µs at an output current of 12 A and
LDP-CWL 06-20 can achieve rise times less than 25 us 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.

14
DC link voltage has to be below 10 V the Vcc and more than 5.5 V
above the compliance voltage to achieve higher bandwidths.
Frequency Response
The following graph demonstrates the 3dB bandwidth for increasing output current values
of the LDP-CWL 06-20. The following measurement results are made on a dummy diode
with a compliance voltage of 10 V.
30,00
35,00
40,00
45,00
50,00
55,00
60,00
1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00
Iout [A]
f [kHz]
The following graph demonstrates the 3dB bandwidth for increasing output current values
of the LDP-CWL 12-20. The following measurement results are made on a dummy diode
with a compliance voltage of 10 V.
100,00
110,00
120,00
130,00
140,00
150,00
160,00
170,00
180,00
190,00
200,00
210,00
220,00
230,00
240,00
250,00
260,00
270,00
280,00
290,00
300,00
1,00 2,00 3,00 4,00 5,00 6,00 7,00 8,00 9,00 10,00 11,00 12,00
Iout [A]
f [kHz]

15
Trigger Delay
The delay between the triggering signal and the load-current is typically
td=2.2 µs.

16
Test oad
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
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 imiter
The LDP-CWL 12-20 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. The scaling of the current
limiter is 0.3 V/A and can be set by the potentiometer. If you want to disable the current
limiter then set the voltage to 4 V. Watch out because you might damage or destroy your
load.

17
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