© 2018
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LDTC0520 / LDTC1020 LASER DIODE AND TEMPERATURE CONTROLLER
WIRE THE TEMPERATURE CONTROLLER
POWER SUPPLIES AND TEST LOADS
to wire the temperature controller power
supplies.
The following voltages need to be verified using the SOA
Calculator with your specific laser and TEC or other loads
before operation.
VDD_FL
3–12 V
Current draw for electronics = 10 mA + laser
VDD_WTC
4.5–12 V
Current draw for electronics = 100 mA + TEC
if VDD_WTC and VS are tied
VS
4.5–30 V
Current draw based on TEC
if VDD_WTC and VS are separate
NOTE: In some cases a single power supply can be used
if the SOA requirements are met and the required power is
obtained to operate your laser and temperature controller.
VDD_FL
VDD_WTC
VS
GND
SP1
SP2
LD SHD (Enable LD current)
COM
EXT LD SETpoint
COM
LD P Monitor
LD I Monitor
ACT T Monitor
SET T Monitor
EXT T SETpoint
COM
J1
J2
V
DD_WTC
V
S
1
1
4
12
Digital
Multi
Meter
Figure 9. Temperature Controller Power Supply and
Monitor Wiring
Next wire the temperature controller test loads, referencing
for details. With the test loads, to stay within the
Safe Operating Area, V
S
must not exceed 5 V.
LDC
PDA
Spare
LDA
COM
TEC+
TEC-
SEN+
SEN-
COM
J3
1
10
10 kΩ
R
LOAD
= 1 Ω, > 10 W
I
METER
Figure 10. Temperature Controller Test Load Wiring
!
Operating the LDTC without a temperature
sensor will drive maximum current through
the tec or heater, potentially damaging it.
SET THE TEMPERATURE CONTROLLER
CURRENT LIMITS
These instructions are for a TEC application with an NTC
thermistor temperature sensor; if you are using a resistive
heater and/or a PTC temperature sensor, refer to
for instructions.
Refer to the TEC datasheet to determine the maximum
allowable drive current (I
LIM
). As seen in
, an
ammeter directly measures the current through the TEC or
R
LOAD
.
Prior to applying power, ensure that all trimpots are turned
completely OFF by turning them a full twelve turns counter-
clockwise.
STEP 1:
Switch on the VDD_WTC and VS power supplies; the
WTC POWER ON LED will illuminate green. As soon as
power is applied, the temperature controller is active and will
drive current through R
LOAD
or the TEC. The SET T Monitor
should read approximately 1 V (default safe temperature
setting).
!
The temperature controller output is
enabled as soon as power is supplied to
V
DD_WTC
and V
S
. The WTC PWR ON LED
illuminates green when power is on to the
temperature controller.
STEP 2:
Attach a voltmeter to the SET T Monitor and increase
(turning clockwise) the T SET trimpot voltage to 0.85 V. This
will allow testing and/or setting of the heating current when
using NTC thermistors
1
.
Monitoring the current through the TEC, rotate LIM B trimpot
to the desired current limit.
STEP 3:
Increase (turning clockwise) the T SET trimpot voltage
to 1.35 V. This allows testing and/or setting of the cooling
current when using NTC thermistors
2
.
Monitoring the current through the TEC, rotate LIM A trimpot
to the desired current limit.
Switch off the power supplies.
1 T SET of 0.85 V corresponds to a temperature setpoint of
approximately 29°C with a 10 kΩ thermistor at the default 100 μA
bias current.
2 T SET of 1.35 V corresponds to a temperature setpoint of
approximately 18°C with a 10 kΩ thermistor at the default 100 μA
bias current.
