IC-WJ Datasheet, PDF (6/12 Pages) IC-Haus GmbH – LASER DIODE DRIVER

iC-WJ, iC-WJZ
LASER DIODE DRIVER
APPLICATIONS INFORMATION
Rev C1, Page 6/12
Laser Power Adjustment
The iC-WJ and iC-WJZ devices can be adapted to CW
laser diodes from approximately 2 to 40 mW. N- and
M-type models can be used.
The pin ISET is used for the adjustment to the sensi-
tivity of the monitor diode and to set the desired optical
laser power. The setpoint for the averaging control of
the monitor diode current is preset at this pin.
RSET
74HCxx
4 ISET
6 IN
REFERENCE
3
REF
THERMAL
SHUTDOWN
INPUT
2
VCC _{POWER DOWN}
REF
4
WATCHDOG
CWD
2
DRIVER
1
VCC 5
C3
2 nF
KLD 8
R1
12 Ω
AMD 7
1:1 iC−WJ
1:3 iC−WJZ
iC−WJ/WJZ
CI
3
CI
470 nF
GND
1
Figure 1: Operation of a laser diode according to the example
+5 V
C1
100 uF
LD
MD
To calculate the current required at ISET, the average
optical laser power is to determine:
Example iC-WJ
Laser diode with 5 mW maximum optical output, mon-
itor diode with 0.13 mA/mW, pulse duty factor set to
20 % with P_peak = 5 mW:
P_av
=
P_peak
∗
t_whi
T
The resulting average optical power is 1 mW and the
average monitor diode current is 0.13 mA. The resistor
RSET is calculated as:
with peak value P_peak and pulse/period duration
twhi
twlo
t_whi /T .
T
Figure 2: Duty cycle
CR1 ∗ V (ISET ) 1 ∗ 1.22 V
RSET =
=
= 9.4 k Ω
I_av (AMD)
0.13 mA
with the Electrical Characteristics No. 301 for V(ISET)
and No. 108 for current ratio CR1.
Example iC-WJZ
Laser diode with 5 mW maximum optical output, mon-
itor diode with 0.75 mA at 3 mW, CW operation (pulse
duty factor 100 %) with P_cw = 1 mW: