© 2018
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LDTC2/2 LASER DIODE DRIVER AND TEMPERATURE CONTROLLER
RECOMMENDED THERMOELECTRIC TEST
LOAD
For the temperature controller, recommended simulated
thermoelectric and thermistor circuits are shown in
and
. Configuring the temperature controller using
test loads is recommended for setting the thermoelectric
controller limits or to check the temperature controller
operation.
R
LOAD
TEC+
(Pin J3-6)
TEC-
(Pin J3-7)
R
LOAD
= 1 Ω, Rated >10 W
TEC Test Load
I
METER
Figure 5. Simulated Thermoelectric Test Load
R1
R1 = 10 kΩ, ¼ W resistor
SEN-
(Pin J3-9)
SEN+
(Pin J3-8)
Simulated Thermistor
Figure 6. Simulated Thermistor
This circuit simulates a 10 kΩ thermistor operating at 25°C.
Use the 100 µA bias current setting to create a 1 V sensor
signal. Other resistor values can be used depending on
the sensor voltage you wish to simulate. To drive cooling
current, set T SET to 1.35 V and to drive heating current, set
T SET to 0.85 V.
NOTE:
To stay within the Safe Operating Area while using
the test load, V
S
must not exceed 5 V.
RECOMMENDED LASER DRIVER TEST LOAD
For the laser diode driver, recommended simulated laser
and
.
1N4001
1N4001
LDC
(Pin J3-1)
LDA
(Pin J3-4)
1 Ω, 2 W
Constant Current Mode
Figure 3. Constant Current Mode Test Load
In Constant Power Mode, the setpoint correlates to the
photodiode feedback current, which represents a fraction
of the light power emitted by the laser diode. Photodiode
current is measured by monitoring LD P MON.
24 Ω
1N4001
1N4001
2N3906
0.33 µF
PDA
(Pin J3-2)
LDA
(Pin J3-4)
LDC
(Pin J3-1)
Constant Power Mode
The 24 Ω resistor typically
produces approximately 30 mA
laser driver current. Vary the
resistor value to change the
output current.
1 Ω, 2 W
Figure 4. Constant Power Mode Test Load
NOTE:
To determine the actual drive current, measure
the voltage drop across the 1 Ω resistor. Do not insert an
ammeter in series with the output circuit; doing so may
cause instability in the control loop. To stay within the Safe
Operating Area while using the test load, V
S
must not exceed
5 V.
