iC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 2/20
DESCRIPTION
Three-channel laser diode pulse regulator iC-NZ en-
ables the continuous wave operation of laser diodes
and spike-free switching with defined current pulses
in a frequency range of up to 155 MHz. The three
channels can be accumulatively pulsed via inputs
LENL, LENM and LENH. The peak optical power of
the laser diodes is regulated separately for high, mid-
dle and low levels and adjusted using the three exter-
nal resistors RMH, RMM and RML.
The iC is activated via pin EN which triggers a self-
test of the device. The system is enabled if no errors
are detected. Any errors are signaled at pin NERR.
The (average) current monitor can be set using ex-
ternal resistor RSI. Overcurrent is signalled at NERR,
causing the iC to be shut down.
To ensure that the selected laser class is maintained
a second monitor input SMD (safety
monitor diode)
is needed. This optional photo diode monitors the
laser power. Exceeding the monitor window, set-up
by RSMD, triggers a permanent reset. This is re-
ported at output NERR and can be deleted when the
system is restarted at EN.
For high pulse frequencies the device can be
switched into controlled
burst mode
at input REGEN.
A previously settled operating point is maintained
throughout the burst phase.
When the iC is switched on all safety-relevant sig-
nals pertinent to the current monitor, SMD and con-
trol unit are checked. These units are in turn mon-
itored for the following: overcurrent, short circuits,
open pins and whether the laser is switched off in
terms of output power. With the exception of the lat-
ter these checks are carried out intermittently dur-
ing operation. So that the device is single-failure-
proof various safety check routines are also imple-
mented. To this end a second SMD (safety
monitor
diode)
monitoring the laser power is required. The
laser power must stay within a defined range during
operation (thus maintaining the laser class). If this
range is left, the system is shut down and an error
message is generated.
ICHAUS [ IC-HAUS GMBH ]
