© 2017
www.teamWavelength.com
10
FL591FL LASER DIODE DRIVER
Configure the setpoint jumpers per
Table 5
. Channels one
and two are configured independently.
Table 5. Setpoint Jumper Configuration
TRIMPOT
BNC
EFFECT
OFF
OFF
This setting results in no setpoint input
signal; Do not use this setting
ON
Reference only the BNC signal
ON
OFF
Reference only the onboard trimpot
ON
Add the BNC signal to the onboard
trimpot setpoint value
When the FL591FL is delivered it is configured to reference
only the onboard trimpot setpoint signals.
CONNECT THE CURRENT AND
POWER MONITORS
Connector J4, the screw terminal at the top of the board,
includes outputs for monitoring the drive current and
photodiode currents of both channels. Wire the DMM per
Figure 2 on page 2
to monitor these signals. The
transfer functions are listed in
Table 2 on page 5
.
ENABLE THE OUTPUT CURRENT
In order to enable the output current, two conditions must
be met simultaneously:
• The DIS pin on the power connector must be grounded.
• The output ENABLE switch must be set to ENABLE.
Channels one and two are enabled simultaneously, whether
the FL591FL is in separate- or parallel-output mode. When
the output is enabled, the LED next to the ENABLE switch
will illuminate.
The output is disabled by floating the DIS pin or applying
a 3 – 5 VDC signal, or by setting the ENABLE switch to
DISABLE.
ADJUST THE OUTPUT CURRENT SETPOINT IN
CONSTANT CURRENT MODE
Calculate the V
SET
voltage value using the equation below.
Use the proper CC-mode transfer function for dual- or
single-channel operation (see
Table 2
).
V
SET
= I
LD
/ Transfer Function
(V)
Connect the positive lead of the DMM to the V
SET1
testpoint,
and the negative lead to the GND testpoint and adjust the
V
SET1
trimpot until the voltage value on the DMM matches
the value calculated above. Turning the trimpot clockwise
increases the output current.
Repeat the process on the second channel if operating in
dual-channel mode.
ADJUST THE OUTPUT CURRENT SETPOINT IN
CONSTANT POWER MODE
In Constant Power mode, the drive current is not set directly.
Rather, the photodiode current setpoint is calculated and
set; the controller adjusts the output current in order to
maintain the required photodiode current.
Refer to the laser diode datasheet to find the photodiode
current at the desired optical output power level. Then
calculate the V
SET
voltage value using the equation below,
and the CP-mode transfer function listed in
Table 2
.
V
SET
= I
PD
/ Transfer Function
(V)
Connect the positive lead of the DMM to the V
SET1
testpoint,
and the negative lead to the GND testpoint and adjust the
V
SET1
trimpot until the voltage on the DMM matches the
V
SET
voltage. Turning the trimpot clockwise increases the
Constant Power setpoint current.
Repeat the process on the second channel if operating in
dual-channel mode.
RECONFIGURE FOR YOUR APPLICATION
Once you are familiar with the operation of the FL591FL,
switch off the output and power supplies, and remove
the test load. Wire your laser diode according to the wire
diagram shown in
Figure 2 on page 2
.
