IC-NE Datasheet, PDF (8/9 Pages) IC-Haus GmbH – LIGHT-GRID PULSE RECEIVER

iC-NE
LIGHT-GRID PULSE RECEIVER
Rev E1, Page 8/9
With no AC photocurrent fractions in the receiver pho-
todiode, approximately equal currents are drawn in SP
and SN. Within a time t_inh ≥ 5 µs, the transient differ-
ential currents in the output stage, caused by switching
the chip on, have decayed, and iC-NE is ready to re-
ceive.
Current is drawn from PD (IC1) by a light pulse on the
photodiode PD1, and the currents at outputs SP and
SN react as shown in Figure 9: I(SP) rises and returns
to the initial value with a time constant determined by
the lower bandpass amplifier cut-off frequency, as long
as the photodiode is constantly illuminated. When the
light pulse decays, the current in SP first sinks and then
ramps up to the standby value. The current in SN has
a mirror-imaged time dependence, as the sum I(SP) +
I(SN) is constant.
With DIN1 = 0, the next rising CLK edge resets FF1
and turns off the currents in the differential output
stage. Simultaneously, FF1 sends the stored informa-
tion to FF2. FF3 also accepts this information with the
trailing CLK edge and activates the bandpass ampli-
fier and the bias in the next device, IC2, via the out-
put driver. The pulse diagram is also valid for the
subsequent components in the chain, i.e. the ICs ar-
ranged as a light curtain form a clock-driven shift reg-
ister which passes on the input information.
DIN1
CLK
Q1(IC1)
DO1
DO2
DO3
RECEIVED
LIGHT PULSE
PD1
PD2
PD3
I(SP)
I(SN)
Figure 9: Signals for the chain configuration of Fig. 8
Light curtain PCB layout
The PCB layout for light curtain receivers is not critical.
The photodiode anode should be directly connected to
iC-NE’s GND pin so that voltage drop caused by the
chip’s operating current is not coupled into the pho-
tocurrent signal.
As the power consumption is relatively small, only low-
level back-up capacitors are required (typically 1 µF
electrolytic capacitor in parallel to 47...100 nF ceramic
capacitor). The ceramic capacitors should be placed at
a distance of 7.5 cm apart, electrolytic capacitors at up
to twice this distance. The number of receivers backed
up as a group in this manner is irrelevant as only one
device is activated and draws current at a time.
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