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 • Extension of the laser current with few external com-
which is single-failure-proof and able to maintain a se- ponents
lected laser class. The device includes the following • Operation of blue laser diodes possible
functions:
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 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
Monitoring the laser current
• External error messaging
iC-NZ monitors the laser current flowing from pin LDA
• Pulses of up to 155 MHz in controlled burst mode, (Figure 5). The DC current threshold is set using a
during which a previously set operating point is main- resistor at pin RSI. If this threshold is exceeded, the
tained
device is shut down for safety reasons.
SDIS
SDIS
VDD
LDA
VDD
CURRENT MONITOR
x500
NSEN
S3
ILDA
CLDA
x1
+
−
S2
0.5V
NEN
VREF
LD MD
RSI
S1
IRS
RSI
NSEN
LDAOK
EN
FINITE STATE MACHINE
Figure 5: Monitoring the laser current
When dimensioning resistor RSI the following applies:
current RSI is calculated as:
0.5V
0.5V
Imax (LDA) = 500×
RSI
RSI = 500×
= 3.5kΩ
70mA
Short pulses with higher currents are also possible as
the DC current is monitored. Capacitor CLDA supplies
the current for short, higher pulses.
Switching up to three laser power levels
The following steps must be taken to set the required
optical power:
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
1. Enabling the system
2. Calibrating the low and middle channels
3. Calibrating the high channel
ICHAUS [ IC-HAUS GMBH ]
