IC-NZ Datasheet, PDF (17/20 Pages) IC-Haus GmbH – FAIL-SAFE LASER DIODE DRIVER

iC-NZ
FAIL-SAFE LASER DIODE DRIVER
MISCELLANEOUS
Rev B2, Page 17/20
Status outputs NERR, NSF and REGEN
Pin NERR is an open-collector output with three states:
I(NERR) = 0 mA
I(NERR) > 1.5 mA
0 < I(NERR) < 1.5 mA
Pin EN is low or the control unit is operational (no error)
N-type laser diode: V(MDL) = 0.5 V
P-type laser diode: V(MDL) = VDD – 0.5 V
Error or iC-NZ is still undergoing its self-test
No error, the control unit is not yet settled or not enough laser light
N-type laser diode: V(MDL) < 0.5 V
P-type laser diode: V(MDL) < VDD – 0.5 V
Pin NSF is also an open-collector output and signals the no safety mode:
I(NSF) > 1.5 mA iC-NZ is in safety mode
operation with a second monitor diode
I(NSF) = 0 mA iC-NZ is in no safety mode operation without a second monitor diode
Pin REGEN, in addition to its mode select input function (regulated output power ↔ burst mode), also signals
the condition of Pin ENCAL by its pull-down current:
Ipd(REGEN) < 10 µA ENCAL = low cf. Item No. 202
Ipd(REGEN) > 100 µA ENCAL = high cf. Item No. 205
Controlled burst mode
In controlled burst mode iC-NZ can pulse with up to
155 MHz, thus making it suitable for use in laser pro-
jection or data transmission. Controlled here means
that a preset operating point is maintained during fast
pulsing or the burst phase.
A low power level is first regulated, for which REGEN
and LENL must be high. Following this the middle or
high power level can be set (LENx → high). The control
unit then switches over to the middle or high channel.
As only one channel can be regulated at any one time
and as the voltage at CIL must not increase by residual
current (this could destroy the laser diode) the capac-
itor at CIL is discharged with a maximum of 100 nA.
Once CIx has been regulated LENx can return to low.
REGEN at low switches into burst mode and thus turns
the control unit off. The preset operating point is main-
tained. To prevent the laser current rising due to resid-
ual current the capacitors for the three channels are
discharged with a maximum of 100 nA. This process
is illustrated in Figure 15. As the capacitors are dis-
charged gradually the output levels must be regulated
again after a certain period. With an integration ca-
pacitance (CIx) of 100 nF, for example, the level must
again be regulated after 500 µs, with this rising to 1 ms
with 200 nF.
EN
REGEN
LENL
LENx
CIL
CIx
I(Laser)
Figure 15: Controlled burst mode
Extending the laser current
iC-NZ also has a high-current mode. Here, the laser
current no longer flows through the iC but passes in-
stead through the external circuitry (RLDA, Q1, iC-HK);
pin RSI is switched to VDD. The current monitor is
still active and the shutdown threshold can be set us-