© 2018
10
WLD SERIES LASER DIODE DRIVERS
OPERATING INSTRUCTIONS
— STANDALONE
WLD CIRCUIT CALCULATOR
automatically calculates
the required external component values based on operating
parameters. Use this tool to quickly and easily configure the
WLD without the calculations found in this section.
SELECT THE LASER DIODE OUTPUT CURRENT
RANGE
The output current range of the WLD3343 depends on the
selection of current sense resistor R
SENSE
placed between
Pin 8 (RS+) and Pin 10 (RS-) as shown in
TYPE A / B Laser Diodes
A
B
GND
V
DD
11
9
10
14
WLD3343
LD
R
SENSE
8
7
RS+
RS-
I
LD
TYPE C Laser Diodes
A
B
GND
V
DD
11
9
10
14
WLD3343
LD
R
SENSE
8
7
RS+
RS-
I
LD
Figure 4. R
SENSE
is connected between Pin 8 and Pin 10.
To calculate R
SENSE
for a maximum desired laser diode current
I
LDMAX
, use
for Constant Power operation and
Equation
for Constant Current. Refer to
to
select R
SENSE
for common laser diode current ranges.
R
SENSE,CP
=
1.25
(3)
I
LDMAX
R
SENSE,CC
=
1.00
(4)
I
LDMAX
I
LDMAX
CONSTANT
POWER
R
SENSE
CONSTANT
CURRENT
R
SENSE
50 mA
25.00 Ω
20.00 Ω
125 mA
10.00 Ω
8.00 Ω
250 mA
5.00 Ω
4.00 Ω
500 mA
2.50 Ω
2.00 Ω
1.25 A
1.00 Ω
0.80 Ω
2.2 A
0.57 Ω
0.45 Ω
WLD3343-3A & WLD3343-3L ONLY:
3 A
0.42 Ω
0.33 Ω
Table 3. Determine the proper sense resistor (R
SENSE
)
value based on maximum output current (I
LDMAX
),
depending on operation mode.
HELPFUL HINTS FOR CHOOSING R
SENSE
•
Never use a carbon film resistor for R
SENSE
.
• Avoid resistors with high parasitic inductance.
•
Select a resistor with a low temperature coefficient
(1% ≈ 100 ppm/°C).
• Place R
SENSE
as close to Pins 8 (RS+) and 10 (RS-) on
the WLD3343 as possible to avoid parasitic resistance
effects from the PCB layout.
• Use
Equation
for determining the power rating of
R
SENSE
.
NOTE:
Wavelength Electronics recommends a conservative
power rating of 2 times normal maximum for R
SENSE
.
Equation
incorporates this recommendation.
P
RATING
= 2 · I
2
LDMAX
· R
SENSE
(5)
CHOOSE OPERATION MODE: CC OR CP
The WLD3343 can operate in either Constant Current or
Constant Power mode. Configuring the WLD operation
mode is accomplished by installing:
•
a 1 kΩ resistor between Pin 5 and Pin 6 for Constant
Current mode.
•
a 0.1 μF capacitor between Pin 5 and Pin 6 for Constant
Power mode.
