Wavelength Electronics FL500, Datasheet And Operating Manual

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OPERATING INSTRUCTIONS
The FL500 requires minimal external electronics. If you are
using the driver on the benchtop or for prototyping your laser
control system, we recommend purchasing the FL591FL
Driver Board.
We recommend using a test load until you are familiar with
operation of the driver. Refer to page 3 for test load
schematics.
NECESSARY EQUIPMENT
The following equipment is the minimum necessary to
configure the FL500 for basic operation:
• FL500 Driver
• Digital Voltmeter, 4-½ digit resolution recommended
• Test load for configuring the driver [optional]
• Laser Diode
• Connecting wires
• Power Supply
STEP 1 - CHOOSE ONE OR TWO POWER
SUPPLIES, VOLTAGES SOURCES
Configure the power supply to provide +3 to +12 VDC.
Connect the positive terminal of the power supply (V
S
) to
Pin 1 and the negative terminal to Pins 9 and/or 10 (PGND)
or Power Ground depending on the FL500 operation
explained in the following steps below. Only ground V
S
to
Pin 2 if it is also grounded to Pins 9 or 10 (see page 9 ).
V
S
powers the laser diode current source (or test load),
and VDD powers the control electronics. Power the laser
diode from VDD by connecting VDD where V
S
is shown.
For lower noise operation, separate VDD from V
S
. V
S
can
be up to 20 V. At this level, however, too much power can
be dissipated in the FL500 causing permanent damage.
Calculate the power dissipated in the FL500 using the Safe
Operating Area (SOA) Calculator online prior to using a
V
S
more than 2 V greater than the voltage dropped over
the laser diode. A maximum power dissipation of 1 W
per source (2 W for paralleled operation) must not be
exceeded.
The minimum V
S
is determined by the voltage drop across
the laser diode and half the setpoint voltage. V
SMIN
= V
LD
+
VSET/2 + 25 mV (across FET). Ground this power supply
at Pins 9 & 10 (PGND). Using Pin 2 could damage the
FL500.
Example V
SMIN
:
V
LD
= 1.2 V
VSET = 1.5 V
V
SMIN
= 1.2 V + (1.5 / 2) + 0.025 = 1.975
STEP 2 - CREATE A SETPOINT
Connect a voltage source to Pins 4 (VSET1) and/or Pins 6
(VSET2) and Pin 5 (GND) to create a setpoint for the current
output. Check the specific configuration step below for more
detailed instructions.
Pick the one of the following three wire configurations
(step 3) that best fits your operation of the FL500.
STEP 3 - CONFIGURE THE WIRING
OPTION 1: OPERATE AS TWO INDEPENDENT
DRIVERS
Connect the positive terminal of a power supply to Pin 4
(VSET1) and the positive terminal of another power supply
to Pin 6 (VSET2). Connect both negative terminals to
Pin 5 (GND). The power supplies do not need to be tied
together. The transfer function for individual VSETs (1 & 2)
is 0.125 A / V. The FL500 contains circuitry for two 250 mA
drivers.
Connect one test load (laser diode) to Pins 11 & 12 (LDC1)
and Pin 1 (VDD). Place the other test load on Pins 7 & 8
(LDC2) and Pin 1 (VDD). Make sure V
S
is grounded at Pins 9
& 10 (PGND). Pin 2 (GND) will also be tied to this ground.
The RESET minimum current is 10 µA, and the leakage
current is less than 1 mA. The FL500 has a known leakage
current when disabled equal to the following magnitude:
I
OUT(LEAK)
=
V
IN
20 kΩ
This is well below 1 mA, and the usual leakage expected is
100 µA.
See Figure 7 for typical operating schematic.
Figure 7. Single Supply Voltage Operating Two Independent
Drivers
Leave Pins 6, 7, 8, and either 9 or 10 floating (or not
connected to a power supply or ground) to limit the output
current of the FL500 to 250 mA by using just one channel.
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FL500 LASER DIODE DRIVER