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IC-HX Datasheet, PDF (7/11 Pages) IC-Haus GmbH – 3-CHANNEL DIFFERENTIAL COLD LINE DRIVER | |||
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iC-HX
preliminary
3-CHANNEL DIFFERENTIAL COLD LINE DRIVER
DESCRIPTION
Rev A1, Page 7/11
Line drivers for control engineering couple TTL- or
CMOS-compatible digital signals with 24 V systems via
cables. The maximum permissible signal frequency is
dependent on the capacitive load of the outputs (ca-
ble length) or, more speciï¬cally, the power dissipation
in iC-HX resulting from this. To avoid possible short
circuiting the drivers are current-limited and shutdown
with excessive temperature.
When the output is open the maximum output voltage
corresponds to supply voltage VB (with the exception
of any saturation voltages). Figure 2 gives the typical
DC output characteristic of a driver as a function of the
load. The differential output resistance is typically 75 â¦
over a wide voltage range.
40
36
VB = 40 V
32
28
24
20
VE = hi
vented by an integrated impedance network, as shown
in Figure 3.
T iCâHX Eingang
iCâHX Ausgang
SPS Eingang
(100 m Leitung)
vert. 8 V/div hor. 2 µs/div
Figure 3: Reï¬ections caused by a mismatched line
termination
During a pulse transmission the amplitude at the iC-
output initially only increases to half the value of sup-
ply voltage VB as the internal driver resistance and
characteristic line impedance form a voltage divider.
A wave with this amplitude is coupled into the line and
experiences after a delay a total reï¬ection at the high-
impedance end of the line. At this position, the re-
ï¬ected wave superimposes with the transmitted wave
and generates a signal with the double wave amplitude
at the receiving device.
16
12
VB = 24 V
8
iCâHX EingangT
iCâHX Ausgang
4
0
0
100
200
300
400
500
âI(A) [mA]
Figure 2: Load dependence of the output voltage
(High-side stage)
Each open-circuited input is set to low by an internal
pull-down current source; an additional connection to
GND increases the deviceâs immunity to interference.
The inputs are TTL- and CMOS-compatible. Due to
their high input voltage range, the inputs can also be
set to high-level by applying VCC or VB.
LINE EFFECTS
In PLC systems data transmission using 24 V sig-
nals usually occurs without a matched line termina-
tion. A mismatched line termination generates reï¬ec-
tions which travel back and forth if there is also no line
adaptation on the driver side of the device. With rapid
pulse trains transmission is disrupted. In iC-HX, how-
ever, further reï¬ection of back travelling signals is pre-
SPS Eingang
(100 m Leitung)
180 ns 760 ns
vert. 8V/div hor. 500 ns/div
Figure 4: Pulse transmission and transit times
After a further delay, the reï¬ected wave also increases
the driver output to the full voltage swing. iC-HXâs inte-
grated impedance adapter prevents any further reï¬ec-
tion and the achieved voltage is maintained along and
at the termination of the line.
A mismatch between iC-HX and the transmission line
inï¬uences the level of the signal wave ï¬rst coupled into
the line, resulting in reï¬ections at the beginning of the
line. The output signal may then have a number of
graduations. Voltage peaks beyond VB or below GND
are capped by integrated diodes. By this way, trans-
misssion lines with a characteristic impedance of be-
tween 30 and 140 ⦠thus permit correct operation of
the device.
iC-xSwitch
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