TROUBLESHOOTING
PROBLEM
POTENTIAL CAUSES
SOLUTIONS
Driver will not switch on
Improperly configured power supply
Carefully check the wiring diagram according to
If operating the FL500 with the Evaluation Board, see the
for details regarding power supply.
Output will not enable
ENABLE Pin not held low
Refer to the RESET/ENABLE control (Pin 3) in
Laser output power too low in
Constant Current mode
Laser voltage setpoint too low
Increase the setpoint by increasing the voltage at Pin 4 & 6
(VSET1 & VSET2). VSET1 & VSET2 may be tied together if
operating in parallel.
Laser current limit too low
The current limit is fixed at 500 mA (250 mA per channel).
The Evaluation Board circuitry adds a variable limit current.
Laser driver is compliance limited
Check the laser diode specifications to determine the forward
voltage (V
F
). Make sure that the FL500 is not compliance
limited.
Refer to the Electrical Specifications table on
. If the
driver is compliance limited, VDD may need to be increased.
Verify that the FL500 will be operating within the Safe
Operating Area if VDD is increased.
Driver will not operate in
Constant Power mode
Not available with the standalone
driver
Constant Power Control is available when the FL500 is
used with the FL591 (Evaluation Board) as well as the
LDTC0520/1020 combination modules.
Transfer functions are
inaccurate
Operating as two 250 mA drivers
instead of one 500 mA driver or
reverse
The Transfer Function for operation as two 250 mA drivers is
0.125 A / V.
The Transfer Function for operation as one 500 mA driver is
0.25 A / V.
This is seen in the Electrical Specifications table on
© 2020
12
FL500 LASER DIODE DRIVER
