© 2001, 2003, 2009
WLD3393
PAGE 7
WLD3393-00400-A Rev F
STEP 6: SET THE LASER DIODE CURRENT LIMIT
The WLD3393 LIM trimpot adjusts the laser diode current limit from zero to the full 200 mA or
2.0 Amps, depending on the laser diode current range selected. For accurate laser diode current limit
confi guration follow these steps sequentially:
1. Connect the demo board’s LDA and LDC terminals directly to an ammeter capable of sensing
your maximum laser diode current. If you are using more than +5VDC power supply
voltage, place a resistor in series with the ammeter to reduce power dissipation across the
WLD. The following equations should be used.
Example calculation: V
S
= +12V, I
LIM
= 2A; R
LOAD
= (12-2.5)/2 = 4.75 ohm; 2
2
*4.75= 19W
Another example: V
S
= +9V, I
LIM
= 0.5A; R
LOAD
= (9-2.5)/0.5 = 13 ohm; (0.5)
2
*13 = 3.25W
2. Confi gure the demo board for Constant Current (CC) mode operation. See Step 2.
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. Turn the SET trimpot clockwise until the desired maximum current is achieved. Turn
the LIM trimpot counter clockwise until the current just begins to decrease. Turn the
SET trimpot back fully counterclockwise.
6. Disable the output current by switching the enable switch to the “OFF” position. Remove power
from
the
WLD3393.
STEP 7: 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.
CONFIGURING THE DEMO BOARD
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
