Datasheet

iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 9/12
Furthermore, the introduction of the watchdog permits
long pulse pauses and activation of the laser diode with
pulse packets.
AMD
2.7..6V
7
3
CI
2
CWD
1
GND
6
IN
4
ISET
8
KLD
5
VCC
MD
LD
S1
100nF
CI
15kΩ
RSET
C3
4.7nF
iC−WJB
REF
WDOG
R1
D1
ZD6V8
C2
100nF
R2
2Ω
47uF
C1
VCC
KLD
AMD
LD supply cord
0..2Ω
Figure 10: CW operation via cable plus protective circuitry
CW Operation
In case of CW operation, the input IN can be con-
nected to the power supply VCC. The pin CWD may
be left open, because the capacitor for the watchdog
is not necessary. The capacitor CI for the averaging
control can be reduced to 100 nF.
Operation of laser diode via cable
It is recommended to connect a capacitor of 1 to 10nF
across the laser diode in order to protect the laser
diode against destruction due to ESD or transients.
This capacitor should be placed close to the laser
diode and not at the beginning of the LD supply line.
An approx. 2 Ω series resistor at pin KLD reduces
the IC power consumption and damps possible reso-
nances of the load circuit caused by the inductive LD
supply line. This resistor is useful for many applica-
tions, also for those which do not operate via cable.
On a PCB the forward path VCC to the laser diode
should be arranged in parallel with the return path to
KLD even when the line is only a few centimeters in
length.
Additional protective components for clipping of strong
positive and negative spikes can be useful, in particu-
lar when contact bouncing occurs in an inductive accu-
mulator power supply line. Elements which come into
question here are D1 and R1 as in Figure 10.