IC-NX Datasheet, PDF (2/10 Pages) IC-Haus GmbH – 8-CHANNEL LIGHT-GRID PULSE DRIVER

iC-NX
8-CHANNEL LIGHT-GRID PULSE DRIVER
Rev C1, Page 2/10
DESCRIPTION
iC-NX is an eight-fold LED pulse driver for light cur-
tain systems and light barriers.
The device, which is controlled by a shift register,
features an adjustable LED current sink with a set
range of 0.4 to 1.8 A (at room temperature). The
three stages of the shift register cell enable data to
be safely transported, free of race conditions, in or-
der to activate the pulse driver connected in a chain
in a light curtain application.
The positive temperature coefficient of the LED cur-
rent sink largely compensates for the decrease in
LED efficiency with a rise in temperature. Active dis-
charge provided by short-circuiting the junction ca-
pacitance of the LED enables steep light pulses to be
generated. The duration of this short circuit is deter-
mined by a monoflop which keeps the discharge path
of the LED at a low impedance. In the event of light
pulses occurring in rapid succession the monoflop is
automatically reset to prevent cross currents.
The current sink common to all eight channels pre-
pares for a light pulse when DIN and subsequently
one of the internal data inputs DIi (i = 1...8) reads a
high signal (NENABLE = lo). With the rising edge of
CLK the first flip-flop in the active channel takes on
the value of DIi and switches the current sink to out-
put LEDi. The LED current sink is disconnected from
the LEDi output with the rising edge of the next clock
pulse. The duration of the LED current pulse is thus
determined by the time difference between two rising
CLK edges and should be no less than 0.5 µs.
The next channel in the chain is activated when at the
falling edge of the second clock pulse the shift regis-
ter transfers the high to output DOi. This must be
enabled by SHEN being high; if this is not the case,
a clock-synchronised reset of the entire chain is trig-
gered.
iC-NX signals a broken LED connection or insuf-
ficient LED current by manipulating the input cur-
rent at enable input SHEN which acts as a bidirec-
tional diagnostic interface. When the device is acti-
vated (NENABLE = lo) the input resistance is usually
2.5 kΩ. The resistor is switched to GND when SHEN
is high and to VDD when SHEN is low.
Should the set LED current not reach its specified
value between two clock pulses a current comparator
switches the input resistor off at SHEN. In the event
of a fault a gap in input current is thus produced at
the enable input which can be analysed externally.
Short circuits at the LED outputs are also verified;
these directly alter data transfer within the shift regis-
ter. An LEDON signal cannot be generated for LED
pins which short circuit with the supply line; the data
shift is blocked, causing the entire shift register to
record zeros. A short circuit from output to output,
however, fills the shift register step by step and sev-
eral LEDs are supplied with partial current. When
the next device in the chain is activated the doubled
power consumption can be recognised by the system
control via the supply line.
iC-NX can be programmed to bridge any channels
with the exception of channel 1. To this end the un-
used LED pins (pins without an LED) are connected
to pin PROG. The corresponding registers are re-
moved from the chain by a bypass and are no longer
relevant to the device’s functions.
In the event of excessive temperature or low volt-
age the shift register is reset and the LED current
sink turned off. Driver and logic outputs are current-
limited and short-circuit-proof, as the device is pow-
ered down with excessive temperature. Integrated
protective diodes prevent destruction by ESD.
iC-NX adheres to safety requirements according to
IEC 1496-1. An optional extended temperature range
of -20 to 85 °C is also available.