iC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 17/20
MISCELLANEOUS
Status outputs NERR, NSF and REGEN
Pin NERR is an open-collector output with three states:
I(NERR) = 0 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
I(NERR) > 1.5 mA
0 < I(NERR) < 1.5 mA 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
again be regulated after 500 µs, with this rising to 1 ms
In controlled burst mode iC-NZ can pulse with up to with 200 nF.
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
EN
REGEN
pulsing or the burst phase.
LENL
A low power level is first regulated, for which REGEN
LENx
and LENL must be high. Following this the middle or
high power level can be set (LENx → high). The control
CIL
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
CIx
current (this could destroy the laser diode) the capac-
itor at CIL is discharged with a maximum of 100 nA.
I(Laser)
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-
Figure 15: Controlled burst mode
ual current the capacitors for the three channels are Extending the laser current
discharged with a maximum of 100 nA. This process iC-NZ also has a high-current mode. Here, the laser
is illustrated in Figure 15. As the capacitors are dis- current no longer flows through the iC but passes in-
charged gradually the output levels must be regulated stead through the external circuitry (RLDA, Q1, iC-HK);
again after a certain period. With an integration ca- pin RSI is switched to VDD. The current monitor is
pacitance (CIx) of 100 nF, for example, the level must still active and the shutdown threshold can be set us-
ICHAUS [ IC-HAUS GMBH ]
