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