Wavelength Electronics FL591FL User manual

ORDERING INFORMATION
PART NO DESCRIPTION
FL591FL Evaluation board with FL500
EASY SETUP SAVES YOU TIME
The FL591FL allows you to quickly and easily prototype your
laser diode driver system using our popular FL500 laser
diode driver chip.
The FL591FL can be congured to drive a single 500 mA
output, or two 250 mA independent outputs by setting
onboard jumpers. The drivers operate in Constant Current
or Constant Power modes.
Onboard current setpoint and limit trimpots mean no external
electronics are required to operate the drivers. Simply
connect the power supply and laser diodes, and you’re ready
to go.
ACCURATELY PROTOTYPE YOUR
LASER CONTROL SYSTEM
The FL591FL features low-noise electronics and low
quiescent current, and the feedback and monitor signals
allow you to accurately characterize your laser controller.
You can transfer the FL500 prototype conguration directly
to your custom laser control system with no surprises.
The FL500 is commonly used in hand-held, portable, and
space constrained applications. The small size and light
weight makes the FL500 ideal for airborne applications,
and the dual-channel output is perfect for sighting-and-
detection applications.
FEATURES AND BENEFITS
• Accurately and efciently characterize the FL500
in your application environment
• Includes FL500 Laser Driver chip already installed
• Utilizes all the safety features of the FL500
»Adjustable current limits
»Slow-start laser diode protection
»Brownout protection
• Onboard trimpots adjust output current and
current limits
• Drive two independent 250 mA channels or a
single 500 mA output
• Switches set the operating mode to Constant
Current or Constant Power
• Operates Type A and Type B Laser Diodes
• Output Enable switch, LED status indicators
• Power and Output cables included
CONTENTS
QUICK CONNECT GUIDE 2
PIN DESCRIPTIONS 4
ELECTRICAL SPECIFICATIONS 6
SAFETY INFORMATION 7
OPERATING INSTRUCTIONS 8
TROUBLESHOOTING 11
TECHNICAL SUPPORT INFORMATION 12
MECHANICAL SPECIFICATIONS 17
CERTIFICATION AND WARRANTY 18
PAGE
Applies to Product Revisions A through C
© February 2017
406-587-4910
www.teamWavelength.com
FL591FL
Laser Diode Driver
DATASHEET AND OPERATING GUIDE
Distributor
[email protected]m
www.amstechnologies-webshop.com

© 2017 www.teamWavelength.com 2
FL591FL LASER DIODE DRIVER
QUICK CONNECT GUIDE
!
ItIs ImperatIve that you verIfy the unIt wIll operate
wIthIn the Internal heat dIssIpatIon safe operatIng
area (soa).
operatIng the drIver outsIde the soa may damage or
destroy the drIver and/or laser.
Visit the Wavelength Electronics website for the most accurate,
up-to-date, and easy to use SOA calculator:
http://www.teamwavelength.com/support/calculator/soa/soald.php
Figure 1 is the top view of the FL591FL, illustrating the
onboard switches, trimpots, and connectors.
When shipped from the factory, the FL591FL is congured to
operate with two independent 250 mA outputs. For information
on conguring the FL591FL to drive a single 500 mA output,
refer to page 9.
Figure 2 is the Quick Connect diagram for the FL591FL
illustrating operation as a two-channel laser diode driver. Two
different laser wiring types are shown.
Current Monitor, I
MON1
Power Monitor, PMON1
LD1 Monitor Ground
Current Monitor, IMON2
Power Monitor, PMON2
LD2 Monitor Ground
LD1 Output
Connector
LD2 Output
Connector
Mode
Switches
Current Limit
Trimpots
Power Supply
Connector
Analog Input
BNC Connectors
Output Enable
Switch
ENABLE
DIS
INPUT 1
INPUT 2
TRIMPOT
TRIMPOT
BNC
BNC
VSET 1
VSET 2
GND
GND
LD1 MODE
CC CP CP CC
LD2 MODE LIM 1 LIM 2
LDA
LDA
PDA
PDA
LDC
LDC
LD 1
MON
1
DS
VS
GND
]ON
]OFF
]ONE
]TWO
]OFF
]ON
LD 2
]S
]P
POWER
RPD1
RPD2
FL500
J4
Figure 1. FL591FL Top View
Figure 2. FL591FL Quick Connect Wiring Diagram
Channel LD1 Output 1
Channel LD1 BNC
Optional External
Setpoint (0 to 2 V)
Channel LD2 BNC
Optional External
Setpoint (0 to 2 V)
OPEN or 3 to 5 V = DISABLE
GND = LD ENABLE
GND
VS
DMM
ENABLE
DIS
INPUT 1
INPUT 2
TRIMPOT
TRIMPOT
BNC
BNC
VSET 1
VSET 2
GND
GND
LD1 MODE
CC CP CP CC
LD2 MODE LIM 1 LIM 2
LDA
LDA
PDA
PDA
LDC
LDC
LD 1
MON
1
DIS
VS
GND
]ON
]OFF
]ONE
]TWO
]OFF
]ON
LD 2
]S
]P
1. Common-Cathode configuration.
2. Laser Anode and Photodiode Cathode common.
Channel LD2 Output 2
POWER
RPD1
RPD2
FL500
J4

© 2017 www.teamWavelength.com 3
FL591FL LASER DIODE DRIVER
QUICK CONNECT GUIDE, CONTINUED
The FL591FL is compatible with Type A and Type B lasers,
but will not drive Type C lasers; see Figure 3.
Type A Laser Diode Type B Laser Diode Type C Laser Diode
Common
Cathode
Laser Diode Anode &
Photodiode Cathode Common Isolated Photodiode
Short the
Laser Diode Anode
to Photodiode Cathode
Common
Anode
Laser Diode Cathode &
Photodiode Anode Common
Figure 3. Laser Type Diagrams
Recommended simulated laser loads are shown in Figure 4.
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.
24 Ω
1N4001
1N4001
2N3906
0.33 µF
PDA
LDA
LDC
1N4001
1N4001
LDC
LDA
1 Ω, 2 W
Constant Current Mode 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. Laser Driver Test Loads

© 2017 www.teamWavelength.com 4
FL591FL LASER DIODE DRIVER
PIN DESCRIPTIONS
Table 1. Pin Descriptions and Wire Colors
PIN NAME CABLE
COLOR PIN DESCRIPTION
Connectors LD1, LD2; Cable FL591-00102-A
1LDA Red
Laser Diode Anode connection. When used in 2x–250 mA mode, LD1 and LD2
are independent and isolated from each other. When used in 500 mA mode, the
current is output via connector LD1 only.
2PDA White
Photodiode Anode connection. When used in 2x–250 mA mode, LD1 and LD2
are independent and isolated from each other. When used in 500 mA mode, the
current is output via connector LD1 only.
3 LDC Black
Laser Diode Cathode connection. When used in 2x–250 mA mode, LD1 and LD2
are independent and isolated from each other. When used in 500 mA mode, the
current is output via connector LD1 only.
Connector J4, Cable FL591-00101-A
1 DIS White
Laser diode shutdown / interlock input, optional. The onboard Enable switch must
be set to ENABLE when this external enable function is used.
TTL-compatible. Enable = Ground; Disable = OPEN or 3 to 5 V.
2 VS Red Power supply positive terminal.
3 GND Black Ground connection for power supply input.
Connectors INPUT 1, INPUT 2
Inner VSET1, VSET2 Positive connection for the external setpoint voltage signal
Shield GND Ground connection for the external setpoint voltage signal
Connector MON, Six-Pin Header
1 IMON1, Current Monitor LD1 laser current monitor output. The signal on this pin is proportional to the
actual laser output current. Transfer function shown in Table 2.
2 PMON1, Power Monitor LD1 photodiode current monitor output. The signal on this pin is proportional to
the photodiode current. Voltage range 0 to 2 V. Transfer function shown in Table 2.
3 LD1 Monitor Ground Low current return for LD1 monitors. Do not use for high current return.
4 IMON2, Current Monitor LD2 laser current monitor output. The signal on this pin is proportional to the
actual laser output current. Transfer function shown in Table 2.
5 PMON2, Power Monitor LD2 photodiode current monitor output. The signal on this pin is proportional to
the photodiode current. Voltage range 0 to 2 V. Transfer function shown in Table 2.
6 LD2 Monitor Ground Low current return for LD2 monitors. Do not use for high current return.

© 2017 www.teamWavelength.com 5
FL591FL LASER DIODE DRIVER
Table 2. Monitor Transfer Functions
FUNCTION OUTPUT
CONFIGURATION TRANSFER NOTE
Current Output Monitor,
IMON1 and IMON2
Separate 0.125 A / V The voltage on IMONx is proportional to the current
output on that channel
Current Output Monitor,
IMON1 + IMON2
Parallel
When operating the FL591FL as a single channel 500 mA driver,
monitor the output current on both IMON1 and IMON2. The total output
current monitor voltage is determined by summing the voltage
measured on both monitors, using the equation:
ILD = (VIMON1 + VIMON2) * 0.125
Current Limit Monitor,
ILIM1 and ILIM2
Separate 0.125 A / V Adjust ILIM1 and ILIM2 to set the current limit on each
channel. See page 9.
Current Limit Monitor, ILIM1 Parallel 0.250 A / V
Adjust only ILIM1 to set the current limit when the
FL591FL is operated in parallel-output mode.
See page 9.
Power Monitor,
PMON1 and PMON2
Separate 500 μA / V 1The voltage on PMONx is proportional to the
photodiode current on that channel.
Power Monitor, PMON1 Parallel 500 μA / V 1
When operating the FL591FL as a single channel
500 mA driver, the photodiode current is monitored
on PMON1.
1. The photodiode feedback transfer function can be changed. See page 12 for details.
Table 3. Setpoint Transfer Functions
OPERATING
MODE
INPUT
CONFIG.
OUTPUT
CONFIG.
VSET TRANSFER
FUNCTION NOTES
Constant
Current
One
Separate 0.125 A / V
Measure the voltage on the VSET1 testpoint; adjust the VSET1
trimpot to set the output current on both channels. The VSET2
trimpot is not used.
Parallel 0.250 A / V
Measure the voltage on the VSET1 testpoint; adjust the VSET1
trimpot to set the output current on both channels. The VSET2
trimpot is not used.
Two
Separate 0.125 A / V
Measure the voltage on the VSET1 and VSET2 testpoints; adjust the
VSET1 and VSET2 trimpots to set the output current level for each
channel.
Parallel 0.125 A / V
The VSET1 and VSET2 voltages drive each channel independently.
The output currents sum. Measure the voltages on the VSET1
and VSET2 testpoints separately, and add them to determine the
effective output current.
Constant
Power
One
Separate 500 μA / V 1
Measure the voltage on the VSET1 testpoint; adjust the VSET1
trimpot to set the photodiode current setpoint. The VSET2 trimpot is
not used.
Parallel 500 μA / V 1
Measure the voltage on the VSET1 testpoint; adjust the VSET1
trimpot to set the photodiode current setpoint. The VSET2 trimpot is
not used.
Two Separate 500 μA / V 1
Measure the voltage on the VSET1 and VSET2 testpoints; adjust the
VSET1 and VSET2 trimpots to set the photodiode setpoint for each
channel.
Parallel __ This conguration is not allowed.
1. The photodiode feedback transfer function can be changed. See page 12 for details.

© 2017 www.teamWavelength.com 6
FL591FL LASER DIODE DRIVER
ELECTRICAL SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS SYMBOL
DUAL-
CHANNEL
OPERATION
SINGLE-
CHANNEL
OPERATION
UNIT NOTE
Supply Voltage VS3 to 9 VDC
Max LD Output Current ILD (2x) 250 (1x) 500 mA
Laser Driver Internal Power Dissipation PMAX 1 W per channel 2 W total W TAMBIENT = 25ºC
Case Operating Temperature TOPR -40 to 85 ºC
Case Storage Temperature TSTG -55 to 125 ºC
Weight 1.7 oz 47.6 g
Size 2.97 x 2.50 x 1.07 inches 75.5 x 63.5 x 27.1 mm
LASER DRIVER
SPECIFICATIONS SYMBOL DUAL- CHANNEL
SINGLE-
CHANNEL UNIT NOTE
CONSTANT CURRENT CONTROL
Short Term Stability, 1 hour 35 to 40 ppm TAMBIENT = 25ºC
Long Term Stability, 24 hours 50 to 75 ppm TAMBIENT = 25ºC
CONSTANT POWER CONTROL
Short Term Stability, 1 hour 0.009 % TAMBIENT = 25ºC
Long Term Stability, 24 hours 0.02 %
OUTPUT
Peak Current IMAX 250 - 260 500 - 520 mA
Compliance Voltage VS – (0.5 * VSET) V IMAX = 500 mA
Rise Time 300 nsec ILD = 500 mA
Fall Time 300 nsec ILD = 500 mA
3dB Bandwidth, Constant Current 500 kHz Sinewave input signal
Delayed Start 100 msec
Slow Start Ramp 15 mA / msec
Depth of Modulation 99 % 100 kHz sinewave
POWER SUPPLY
Power Supply Voltage VS3 to 9 V
Quiescent Current, VS100 mA at VS= 9 V
V SET INPUT
Input Impedance 51.1 Ω
Input Voltage Range VSET1, VSET2 0 to 2 V
Damage Threshold VSET < -0.3, VSET > (VS+ 0.3) V
NOISE
Noise and Ripple (RMS) 3µA ILD = 100 mA
Leakage Current with output disabled
50
100
150
µA
VSET = 0 V
VSET = 1 V
VSET = 2 V

© 2017 www.teamWavelength.com 7
FL591FL LASER DIODE DRIVER
THEORY OF OPERATION
The FL591FL employs Wavelength’s FL500 laser diode
control chip, and can drive a single output up to 500 mA or
dual outputs up to 250 mA each.
When operating with two separate outputs, the FL591FL can
be congured to use a single setpoint to drive both outputs
to the same current, or use separate setpoint signals to
drive each current source independently.
It may be useful to remember that you do not directly set the
drive current setpoint; instead, you adjust a voltage signal
that represents the output current. The setpoint voltage is
controlled by the onboard trimpot or by an external input.
The current source continually monitors the actual output
current, compares it to the setpoint, and adjusts the current
if there is a difference between the two signals.
As current is driven through the load, there is a voltage drop
across the load because of the impedance. As the current
increases the voltage drop may increase to the point that it
reaches the Compliance Voltage limit of the current source.
Once that occurs the current source is no longer able to
increase the current driven to the load even if you increase
the setpoint.
The current sources can be operated in Constant Current
(CC) mode or in Constant Power (CP) mode. In CP mode,
the photodiode (PD) current is used in the feedback loop,
and the driver adjusts the output current in order to keep the
PD current constant.
The laser driver includes features that help protect your
laser and make the driver more versatile in a wide array of
applications:
• The current limit is set by an onboard trimpot and
protects the laser from over-current conditions.
• Slow-start delays the current ramp by 100 msec,
and then ramps the current to setpoint at a rate
of 15 mA / msec.
• The photodiode feedback control loop allows for
Constant Power operation whereby the driver adjusts
the laser forward current in order to maintain a constant
photodiode current.
SAFETY INFORMATION
SAFE OPERATING AREA — DO NOT EXCEED
INTERNAL POWER DISSIPATION LIMITS
Before attempting to operate the FL591FL, it is imperative
that you rst determine that the FL500 will operate within the
Safe Operating Area (SOA). Operating the unit outside of
the SOA may damage the controller or the laser. Operating
outside of the SOA will void the warranty.
Go to the Wavelength Electronics website for the most
accurate, up-to-date, and easy to use SOA calculators:
http://www.teamwavelength.com/support/calculator/soa/soald.php
SOA charts are included in this datasheet for quick reference
(page 15), but we recommend you use the online tools
instead.
!
toensure safe operatIon of the fl591fl drIver, It
Is ImperatIve that you determIne If the fl500 Is
goIng to be operatIng wIthIn the Internal heat
dIssIpatIon safe operatIng area (soa).

© 2017 www.teamWavelength.com 8
FL591FL LASER DIODE DRIVER
OPERATING INSTRUCTIONS
The rst step in operating the controller is to wire it, and
connect a test load. It is critical to properly set the drive
current limit before connecting a laser.
We recommend using a test load until you are familiar with
operation of the driver and have congured it to safely power
your laser. A test load design is provided on page 3.
NECESSARY EQUIPMENT
The following equipment is the minimum necessary to
congure the FL591FL for basic operation.
• FL591FL controller, plus included cables
• VS – power supply for the laser driver electronics and the
laser diode; must be rated for 1.1-times the maximum
laser drive current plus 100 mA quiescent current
• Digital multimeter, 4-½ digit resolution recommended
• Test Load (recommended)
• Laser diode
• Connecting wires
SAFE OPERATING AREA AND
THERMAL DESIGN CONSIDERATIONS
SOA charts are included in this datasheet for quick reference,
but we recommend you use the online tools instead. Refer
to the SOA calculator for the FL500.
http://www.teamwavelength.com/support/calculator/soa/soald.php
!
toensure safe operatIon of the fl591fl
controller, It Is ImperatIve that you determIne If the
unIt Is goIng to be operatIng wIthIn the Internal heat
dIssIpatIon safe operatIng area (soa).
PREVENT DAMAGE FROM
ELECTROSTATIC DISCHARGE
Before proceeding, it is critical that you take precautions to
prevent electrostatic discharge (ESD) damage to the driver
and your laser. ESD damage can result from improper
handling of sensitive electronics, and is easily preventable
with simple precautions.
Enter the search phrase “ESD Precautions for Handling
Electronics” in an internet search engine to nd information
on ESD-safe handling practices.
We recommend that you always observe ESD precautions
when handling the FL591FL and laser diodes.
ONBOARD CONTROLS AND MONITORS
Figure 5 shows the jumpers and switches that congure the
FL591FL operating mode.
Mode
Switches
Current Limit
Trimpots
Output Configuration
Jumper (JP2)
Current Limit
Testpoint
ENABLE
DIS
INPUT 1
INPUT 2
TRIMPOT
TRIMPOT
BNC
BNC
VSET 1
VSET 2
GND
GND
LD1 MODE
CC CP CP CC
LD2 MODE LIM 1 LIM 2
LDA
LDA
PDA
PDA
LDC
LDC
LD 1
MON
1
DIS
VS
GND
]ON
]OFF
]ONE
]TWO
]OFF
]ON
LD 2
]S
]P
RPD1
RPD2
FL500
POWER
Output Enable
Switch and LED
Power ON LED
Input Configuration
Jumper (JP1)
Current Monitor, IMON1
Power Monitor, PMON1
LD1 Monitor Ground
Current Monitor, IMON2
Power Monitor, PMON2
LD2 Monitor Ground
Output Disable
Power Supply VS
Power Supply Ground
J4
Figure 5. FL591FL Conguration Controls
The FL591FL can be congured to drive two separate
250 mA outputs with tied or separate setpoints, or a single
500 mA output controlled by a single setpoint.
The control mode—Constant Current or Constant Power—
is set by onboard switches. The current limit for each
channel is set by the trimpots.
SET THE INPUT CONFIGURATION JUMPER
The Input Conguration Jumper (JP1), located between
the BNC connectors, determines whether a single setpoint
signal controls the output current, or if two independent
input signals are used to control each output separately.
Refer to Table 4. Set the jumper to position ONE for single
setpoint operation; set the jumper to position TWO for
independent input signals.
Table 4. Jumper Conguration Overview
JP1 INPUTS
ONE Input 1 controls both output channels
TWO Setpoint signals are separated
* When JP1 is set to position ONE, the FL591FL references
the setpoint signal on Input 1. Any setpoint signal on Input 2
is disregarded.
When the FL591FL is delivered, the default conguration is
to use two independent input signals (jumper set to TWO).

© 2017 www.teamWavelength.com 9
FL591FL LASER DIODE DRIVER
SET THE OUTPUT CONFIGURATION JUMPER
The Output Conguration Jumper (JP2), located between
the output connectors, determines whether the outputs are
paralleled to drive up to 500 mA output on a single channel,
or separate to drive up to 250 mA on two channels.
When the driver outputs are separate, connect each laser
diode to the respective output connector, LD1 and LD2.
When the driver outputs are paralleled, each channel
drives one-half of the total output current. When operating
in parallel driver mode, use output connector LD1 to drive
current to the load.
When the FL591FL is delivered, the default conguration
is with two separate 250 mA output channels (jumper set
to “S”).
WIRE THE POWER SUPPLY AND TEST LOAD
Wire the FL591FL power supply according to Figure 2, use
the test load shown in Figure 4.
When the power supply is switched on, power is applied
to the FL500 and the POWER LED will illuminate, but the
output current is not enabled.
SET THE DRIVE CURRENT LIMITS;
SEPARATE OUTPUT CONFIGURATION
First calculate the VLIM voltage; use the transfer function on
page 5 according to your input/output conguration:
VLIM = ILIMx / Transfer Function (Separate) (V)
Connect the DMM to the LIM1 testpoint and the GND
testpoint, and apply power to the FL591FL. Adjust the LIM1
trimpot until the voltage displayed on the DMM matches the
VLIM value calculated above. Turn the trimpot clockwise to
increase the current limit.
Connect the DMM to the LIM2 testpoint, and set the current
limit on channel two using the same procedure.
SET THE DRIVE CURRENT LIMITS;
PARALLEL OUTPUT CONFIGURATION
If the FL591FL is congured to drive paralleled outputs, the
current limit is set using the LIM1 trimpot only.
First calculate the VLIM voltage; use the transfer function on
page 5 based on your input/output conguration:
VLIM = ILIM1 / Transfer Function (Parallel) (V)
Connect the DMM to the LIM1 testpoint and the GND
testpoint, and apply power to the FL591FL. Adjust the LIM1
trimpot until the voltage displayed on the DMM matches the
VLIM value calculated above.
CONFIGURE FOR CONSTANT CURRENT OR
CONSTANT POWER MODE
The FL591FL will drive lasers in Constant Current mode or
Constant Power mode. Constant Power mode operation
requires photodiode feedback from the laser.
To congure channel one for Constant Current mode
operation, set the LD1 MODE switch to CC (left); for
Constant Power mode set the switch to CP (right). Set
channel two in the same manner.
!
donot change swItch posItIons whIle power Is
applIed to the fl591fl. doIng so may damage the
laser. remove power from the fl591fl board
before changIng mode swItch posItIons.
If the FL591FL outputs are paralleled and operated in
CP-mode, the signal on the channel one photodiode is used
in the control feedback loop.
When the FL591FL is delivered, the default conguration is
Constant Current mode on both channels.
SET THE INPUT SIGNAL CONFIGURATION
Figure 6 shows the setpoint adjust section of the FL591FL.
ENABLE
DIS
INPUT 1
INPUT 2
TRIMPOT
TRIMPOT
BNC
BNC
VSET 1
VSET 2
GND
LD1 MODE
CC CP
]ON
]OFF
]ONE
]TWO
]OFF
]ON
Channel 2 Controls
V
SET Testpoints
Channel 1 Controls
LD1 MODE
CC CP
FL500
Figure 6. Current Setpoint Section
The drivers can be congured to reference only the signal
input on the BNC connector, only the onboard trimpot, or
the sum of the two signals. This versatility allows the driver
to be congured with a bias current set by the trimpot, and
an external modulation signal input on the BNC.

© 2017 www.teamWavelength.com 10
FL591FL LASER DIODE DRIVER
Congure the setpoint jumpers per Table 5. Channels one
and two are congured independently.
Table 5. Setpoint Jumper Conguration
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 congured 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 oating 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 VSET voltage value using the equation below.
Use the proper CC-mode transfer function for dual- or
single-channel operation (see Table 2).
VSET = ILD / Transfer Function (V)
Connect the positive lead of the DMM to the VSET1 testpoint,
and the negative lead to the GND testpoint and adjust the
VSET1 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 nd the photodiode
current at the desired optical output power level. Then
calculate the VSET voltage value using the equation below,
and the CP-mode transfer function listed in Table 2.
VSET = IPD / Transfer Function (V)
Connect the positive lead of the DMM to the VSET1 testpoint,
and the negative lead to the GND testpoint and adjust the
VSET1 trimpot until the voltage on the DMM matches the
VSET 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.