iC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 9/20
DESCRIPTION OF FUNCTIONS
iC-NZ is a three-channel laser diode pulse regulator
which is single-failure-proof and able to maintain a se-
lected laser class. The device includes the following
functions:
• Monitoring of the laser current
• Switching of three laser light intensity levels which
are regulated separately
• Single-failure-proof via laser light monitoring using a
second monitor diode and shut-down of the laser in
the event of error via three separate, independent
switches
• External error messaging
• Pulses of up to 155 MHz in controlled
burst mode,
during which a previously set operating point is main-
tained
• Extension of the laser current with few external com-
ponents
• Operation of blue laser diodes possible
To simplify the initial operation of iC-NZ the following
passage first outlines the basic steps involved and then
goes on to provide details referring to the demo board
available for evaluation. A HL6339G HITACHI laser
diode has been used here by way of example.
Monitoring the laser current
iC-NZ monitors the laser current flowing from pin LDA
(Figure 5). The DC current threshold is set using a
resistor at pin RSI. If this threshold is exceeded, the
device is shut down for safety reasons.
SDIS
VDD
VDD
CURRENT MONITOR
x1
NEN
VREF
S2
NSEN
S3
+
−
ILDA
x500
SDIS
LDA
CLDA
0.5V
LD
RSI
S1
IRS
RSI
LDAOK
NSEN
MD
EN
FINITE STATE MACHINE
Figure 5: Monitoring the laser current
When dimensioning resistor RSI the following applies:
I
max
(LDA) = 500
×
0.5
V
RSI
current RSI is calculated as:
RSI
= 500
×
0.5
V
= 3.5
k
Ω
70
mA
Short pulses with higher currents are also possible as
the DC current is monitored. Capacitor CLDA supplies
the current for short, higher pulses.
Demo board
According to the manufacturer’s specifications laser
diode HL6339G requires a maximum current of 70 mA
for an optical power of 5 mW. For this maximum 70 mA
Switching up to three laser power levels
The following steps must be taken to set the required
optical power:
1. Enabling the system
2. Calibrating the low and middle channels
3. Calibrating the high channel
ICHAUS [ IC-HAUS GMBH ]
