iC-MZ
DIFFERENTIAL HALL SWITCH
Rev A2, Page 8/11
APPLICATON NOTES
The complementary line driver couples the output sig-
nals via lines to industrial 24 V systems. Due to the
possible event of short circuiting in the line the drivers
are current limited and shut down with excessive tem-
perature. The maximum possible signal frequency de-
pends on the capacitive loading of the outputs (line
length) or the power dissipation in iC-MZ caused by
such. With an unloaded output the maximum output
voltage is equivalent to supply VB - with the exception
of the saturation voltages.
40
36
32
28
LINE EFFECTS
With 24 V signals data is often transmitted without
the line beeing terminated with the characteristic
impedance. Mismatched line terminations such as
these cause reflections which travel back and forth if
no suitable adjustments have been made at the driver
end of the setup. With rapid pulse trains transmission
is then disrupted.
In iC-MZ the reflection of return signals is hindered by
an integrated impedance adapter. On pulse transmis-
sion the amplitude at the iC-MZ output first rises to ap-
proximately half the value of supply voltage VB as the
internal driver resistor and the line impedance adapter
form a voltage divider. Following a delay determined by
the length of the line the impedance coupled into the
line in this way is reflected at the high impedance end
of the setup and travels back towards the driver. As the
latter is well adjusted to the line by its interior resistor,
the return pulse is largely absorbed. Fast signals can
thus also be transmitted in this manner along lines with
a characteristic impedance of between 40 and 110
Ω.
BOARD LAYOUT
The thermal dissipation of iC-MZ is improved by con-
necting the thermal pad on the underside to a large
area of copper on the board. Blocking capacitors used
to filter the local iC supply should be connected up
to the VB and GND package pins across the shortest
possible distance.
NERR connection
Excessive temperature and overvoltage errors are in-
dicated at output NERR. In normal operating mode the
pin is at high impedance (open drain); it is switched
to GND in the event of error. It can be connected up
to VB via an external resistor. If NERR is not used, it
must be left open and not be connected to GND.
VB = 36 V
V(D, ND) [V]
24
20
16
12
VB = 24 V
8
4
0
0
100
200
300
400
500
- I(D, ND) [mA]
Figure 8: Load dependence of the output voltage
Figure 8 illustrates the typical highside output charac-
teristics of a driver acting as a load for two different
supply voltages. Across a wide range the differential
output resistance is typically 75
Ω.
ICHAUS [ IC-HAUS GMBH ]
