© 2018
5
LDTC2/2 LASER DIODE DRIVER AND TEMPERATURE CONTROLLER
Table 2. Monitor & Setpoint Transfer Functions
FUNCTION
EQUATION
DESCRIPTION
Monitor Transfer Functions
Laser Diode Forward Current
Measurement
I
LD
=
V
LD I M
2·R
SENSE
Converts voltage output of Laser Diode Current Monitor (Pin 8,
Connector J2) to forward current through Laser Diode.
Default R
SENSE
is 0.4 Ω.
Monitor Photodiode
Current Measurement
(Constant Power Mode)
I
PD
=
V
LD P M
2·R
PD
Converts voltage output of Laser Diode Power Monitor (Pin 7,
Connector J2) to forward current through Photodiode.
[2]
R
PD
= 499 Ω for 2.0 mA range
R
PD
= 4.99 kΩ for 200 μA range
Monitor Photodiode
Current Measurement
(Constant Current Mode)
I
PD
=
V
PD MON
R
PD
Converts voltage output of Photodiode Monitor (Pin 2, Connector J2) to
forward current through Photodiode.
[2]
R
PD
= 499 Ω for 2.0 mA range
R
PD
= 4.99 kΩ for 200 μA range
NOTE: Available on Rev. B and later.
Actual Temperature
1 V / V
Monitors the actual temperature.
Setpoint Transfer Functions
Laser Diode Current
I
LD
=
V
R LD SET
2·R
SENSE
Converts Setpoint Voltage to Laser Diode current.
Default R
SENSE
is 0.4 Ω.
Photodiode Current
(Constant Power Mode)
I
PD
=
V
R LD SET
2·R
PD
Converts Setpoint Voltage to Photodiode current.
[2]
R
PD
= 499 Ω for 2.0 mA range
R
PD
= 4.99 kΩ for 200 μA range
Temperature Setpoint
1 V / V
Monitors the temperature setpoint.
[2]
R
PD
is set with the onboard PDset jumper. See
for details on configuring this jumper.
Determining Revision:
The product revision is indicated within the serial number. Find the serial number labeled on the
PCB. Revision is the third character. Example: 00
B
1730002 would be Revision B of the LDTC2/2.
