© 2020
13
PLDXK-CH SERIES LASER DIODE DRIVER
CALCULATE THE MONITOR VOLTAGES
Refer to the datasheet for your laser to determine the
maximum forward current, and calculate the current limit
monitor voltage (V
) using this equation and the transfer
function found in
:
V
LMON
= I
LIMIT
/ Transfer Function
If you are using the PLDxK-CH in Constant Current mode,
calculate the monitor voltage for the drive current setpoint.
Refer to the datasheet for your laser to determine the
nominal forward current, and calculate the IMON voltage
using the transfer function found in
:
V
IMON
= I
LD
/ Transfer Function
If you are using the PLDxK-CH in Constant Power mode,
calculate the photodiode current monitor voltage, PMON.
Refer to the laser diode datasheet to determine the nominal
photodiode current at the desired operating point. Calculate
the PMON voltage using the transfer function found in
V
PMON
= I
PD
/ Transfer Function
SET THE CURRENT LIMIT
Connect the positive lead of the digital multimeter to the
LMON pin (J2:2), and the negative lead to the COMMON
terminal.
for control locations on the PLDxK-CH:
•
Ensure the external Enable switch is OPEN.
• Switch on the 5 volt power supply to the PLDxK-CH.
• Set the
OUT ADJUST
trimpot to zero by turning at least
12 turns counter-clockwise.
•
Set the current limit by turning the LIM I ADJUST trimpot
until the voltage displayed on the multimeter matches
the value calculated above.
Switch off the power supply.
The PLDxK-CH controllers trip the current limit circuit below
the expected limit level, by 0.2 V on the monitor. To trip the
current limit at exactly the desired current level, refer to
Set the Current Limit More Accurately on page 15
fine-tune the current limit.
ONBOARD ADJUSTMENTS AND CONTROLS
Onboard controls are on the top of the PLDxK-CH and
must be set according to the operation mode. The controls
* DO NOT change switch positions while the output
is enabled; Doing so may damage the laser diode.
!
H1
J1
PDC
PDA
PLD K-CH
LIM I
ADJ - I DISABLED
OUT
ADJ - OUT ENABLED
LASER DIODE DRIVER
CP/CC
PD - Lo/Hi
LDC
LDA
+5V
GND
Setpoint Adjust (12-turn)
Operating Mode *
PD Range *
L = 15 – 500 µA
H = 50 – 5000 µA
CP = Constant Power
CC = Constant Current
J1
J3
J2
Limit Adjust (12-turn)
Current Limit LED
Output Enabled LED
H1
PIN 1: COMMON
Photodiode Output (PD OUT - type C lasers only)
Enabled Status (LD STATUS)
Output Enable (LD ENABLE)
Modulation Input (ANALOG IN)
Photodiode Voltage (PDV - type C lasers only)
PIN 1: COMMON
Limit Current Monitor (LMON)
Photodiode Current Monitor (PMON)
Current Monitor (IMON)
Figure 12. PLD Driver Adjustments and Controls
SET THE CONTROL MODE
Set the MODE switch to CP (left) for Constant Power mode
operation, or to CC (right) for Constant Current mode.
Constant Power mode operation requires a photodiode
feedback loop from the laser diode.
!
Do not switch the control mode while the
output is enabled and driving a laser
diode. The laser diode may be damaged or
destroyed.
SET THE PHOTODIODE RANGE
Two photodiode feedback current ranges are available on
the PLDxK-CH drivers. Reference the datasheet for your
laser diode to find the nominal photodiode current, and set
the PD RANGE switch as follows:
•
Lo (left) = Low Range, PD current 15 – 500 µA
•
Hi (right) = High range; PD current 50 – 5000 µA
!
Do not switch the PD Range while the
output is enabled and driving a laser
diode. The laser diode may be damaged or
destroyed.
