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