© 2018
14
LDTC2/2 LASER DIODE DRIVER AND TEMPERATURE CONTROLLER
ADDITIONAL TECHNICAL
INFORMATION
This section includes useful technical information on the
following topics:
•
Steps For Replacing The WTC/WLD
•
Proportional Gain & Integrator Time Constant – PI
•
Configuration For Alternate Temperature Sensors
•
Changing The Laser Diode Output Current Range
•
•
Temperature Controller Block Diagram
•
Safe Operating Area Calculation
STEPS FOR REPLACING THE WTC/WLD
Disassemble the LDTC2/2:
1. Remove cables from the unit.
2. Remove screw from top of unit holding the cover down.
3. Lift straight up on the cover to remove it from the base.
4. Remove PCB from the base plate by carefully pulling it
straight up off the corner posts. Be sure not to bend the
pins on the WTC/WLD, which will not come off with the
PCB.
5. Remove the eight screws on the bottom of the baseplate
that attach the WLD and WTC to the baseplate.
6. Use a small screwdriver to separate the WLD and WTC
from the baseplate.
Reassemble the LDTC2/2:
1. Plug the new part(s) into the PCB before attaching it to
the base to ensure that the pins do not get bent.
2. Make sure that the thermal sil pad or thermal paste is in
good shape in order to tightly couple the WLD/WTC heat
spreader to the mounting plate or heat sinking surface.
Replace a questionable sil pad or spread a new thin coat
of thermal paste.
3. Seat the holes on the PCB onto the corner posts and
press PCB into seated position. Install the eight screws
in the WLD and WTC.
4. Install the cover and cables.
PROPORTIONAL GAIN & INTEGRATOR TIME
CONSTANT – PI TERMS
The LDTC2/2 is configured to the mid-range positions
appropriate for most laser diode loads. To adjust these
parameters to optimize the temperature control system time
to temperature or stability, contact Wavelength.
CONFIGURATION FOR ALTERNATE
TEMPERATURE SENSORS
LM335
To use a National Semiconductor LM335 temperature sensor
with the LDTC2/2, attach the LM335 cathode to
and the LM335 anode to SENSOR-. R
BIAS
, shown in
should be changed to 2 kΩ for a bias current of
1mA through the sensor.
The voltage output of the LM335 is 10 mV/K.
NOTE: The ExtTset must be used for setting the temperature
when using the LM335.
AD590
To use an Analog Devices AD590 temperature sensor with
the LDTC2/2, first remove R
BIAS
.
Connect the positive lead of the AD590 to a VDD voltage
supply ≥8 V and the negative lead to the pin
on the LDTC2/2. The AD590 produces a current of 1 μA/K,
giving a transfer function of 10 mV/K with a 10 kΩ resistor
connected between and ground (Pins 8 & 9 on
J3).
RTD
To use an RTD, the bias current resistor R
BIAS
)
must be changed to yield either 1 mA (R
BIAS
= 2 kΩ) or 10 mA
(R
BIAS
= 200 Ω) bias current depending on the temperature
range required. Additionally, reverse the connections to
TEC+ and TEC-.
1
1
1
CC
CP
+
ON
OFF
Tset
LIMA
LIMB
ILIM
ISET
+
+
J1
J2
J3
ExtTset Vset PDset
3
2
1
10
9
8
7
6
5
4
3
2
1
12
11
10
9
8
7
6
5
4
3
2
1
R
BIAS
R
35
+
+
+
+
+
Figure 11. Location of Sensor Bias Resistor (R
BIAS
).
