Wavelength Electronics WLD3343, Datasheet And Operating Manual

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WLD SERIES LASER DIODE DRIVERS
CONFIGURE THE LASER DIODE CURRENT
LIMIT
The WLD3343 allows a customized current range for
a specific application. This allows optimized setpoint
resolution while minimizing output noise. The current limit
is set by properly choosing the limit resistor (R
LIM
) and
installing it between Pins 6 and 7.
There are two methods of choosing the appropriate
resistance value R
LIM
. The first uses the normalized
maximum output current and Table 5 . The second is a
calculation using Equation (7) . Both methods depend on
the laser diode type and mode of operation.
Method 1:
To find the normalized maximum output current, divide the
desired laser diode current limit (I
LDLIM
) by the maximum
laser diode current (I
LDMAX
), as shown in Equation (6) .
Then, choose the resistance value of R
LIM
shown next to the
calculated normalized maximum output current in Table 5 .
I
MAX,NORM
=
I
LDLIM
(6)
I
LDMAX
For example, consider using a Type A/B laser diode in
Constant Current mode. If the WLD is configured to output
a maximum current of 2.2 A, and the user wishes to set the
limit current at 1.5 A, then the normalized maximum output
current is 0.68 (1.5/2.2). This value then yields a value of
R
LIM
equal to 405 Ω (from
Table 5
)
Method 2:
To precisely calculate the value of R
LIM
, use
Equation (7)
,
and
Table 4
for the values of α and β.
R
LIM
=
α
I
LDLIM
R
SENSE
+1
(7)
β
1-
I
LDLIM
R
SENSE
+1
β
LASER DIODE TYPE – MODE α β
Type A/B – CC 282 2.85
Type A/B – CP 350 3.35
Type C – CC 290 2.93
Type C – CP 385 3.57
Table 4. Values of α and β to calculate R
LIM
given laser
type and operation mode.
Setting Current Limits Using Trimpots
Connect a 500 Ω trimpot and a 150 Ω resistor as shown in
Figure 5 to make the maximum current limit adjustable.
GND
7
WLD3343
R
LIM
6
LIM
CW CCW
W
150 Ω
500 Ω
SINGLE TURN
TRIMPOT
Figure 5. Use the configuration shown for adjustable current
limits.
I
MAX,NORM
TYPE A/B
CC
R
LIM
( Ω )
TYPE A/B
CP
R
LIM
( Ω )
TYPE C
CC
R
LIM
( Ω )
TYPE C
CP
R
LIM
( Ω )
0.00 152 149 150 150
0.04 162 160 160 160
0.08 172 171 169 171
0.12 183 183 179 183
0.16 194 195 190 195
0.20 205 208 201 207
0.24 217 222 213 220
0.28 230 236 225 234
0.32 243 251 238 248
0.36 257 267 251 263
0.40 272 284 265 279
0.44 288 301 280 295
0.48 305 320 296 313
0.52 322 340 313 331
0.56 341 361 330 350
0.60 361 383 349 370
0.64 382 406 369 392
0.68 405 432 390 414
0.72 429 459 412 438
0.76 455 488 436 463
0.80 483 519 462 490
0.84 514 552 490 519
0.88 547 588 519 550
0.92 582 627 551 583
0.96 621 670 586 618
1.00 664 716 624 656
Table 5. Choose R
LIM
as a function of normalized
maximum output current, laser diode type, and operation
mode.
Use the online WLD Circuit Calculator to automatically determine
values for external components.
www.teamwavelength.com/support/design-tools/wld-calculator/