www.teamWavelength.com
© 2013
WLD3393
PAGE 10
WLD3393-00400-K
STEP 7: SET THE LASER DIODE CURRENT LIMIT
The WLD3393 LIM trimpot adjusts the laser diode current limit from zero to the full 200 mA or 2.2 A,
depending on the laser diode current range selected. For accurate laser diode current limit con
fi
guration
follow these steps sequentially:
1. Connect a test load across the LDA and LDC terminals of the WLD3393. Wavelength recommends
using a power resistor: calculate the resistor value using these two equations.
Example calculation: V
S
= +12 V, I
LIM
= 2 A; R
LOAD
= (12-2.5)/2 = 4.75
; 2
2
*4.75= 19 W
Another example: V
S
= +9 V, I
LIM
= 0.5 A; R
LOAD
= (9-2.5)/0.5 = 13
; (0.5)
2
*13 = 3.25 W
Connect a voltmeter across the resistor. This voltmeter will be used to monitor the output current
while setting the current limit. Refer to the datasheet for your laser diode and
fi
nd the manufacturer’s
recommended current limit, then calculate the V
LIMIT
value as follows:
V
LIMIT
= I
LIMIT
/ R
LOAD
2. Con
fi
gure the evaluation board for Constant Current (CC) mode operation. See Step 3.
3. Turn the SET trimpot fully counter clockwise (OFF). Adjust the LIM trimpot fully clockwise (ON).
4. Apply power to the WLD3393 and enable the output current by switching the enable switch to the
“ON” position. See Figure 1 to locate the switch.
5. Adjust the SET trimpot clockwise until the voltmeter displays the V
LIMIT
value calculated in number 1
above. Next, turn the LIM trimpot counter-clockwise until the displayed voltage just begins to
decrease. Finally, turn the SET trimpot fully counter-clockwise to zero the output current.
6. Disable the output current by switching the enable switch to the “OFF” position. Remove power
from the WLD3393.
7. Return the Mode Switch to CC or CP, according to your application.
STEP 8: CONNECT THE LASER DIODE AND MONITOR PHOTODIODE
With power removed from the WLD3393 board, connect the output (4 wire cable) to your laser diode
as indicated in Table 1. Firmly press the output cable into the output connector.
Table 1: Output Cable Color Code
Wire Color
Function
PIN #
RED
GREEN
WHITE
BLACK
1
2
3
4
LDA
PDC
PDA
LDC
R
LOAD
= V
S
- 2.5
I
LIM
R
LOAD
power rating = I
2
LIM
* R
LOAD
CONFIGURING THE EVALUATION BOARD
