IC-VX Datasheet, PDF (8/11 Pages) IC-Haus GmbH – 3-CHANNEL DIFFERENTIAL LINE DRIVER

iC-VX
3-CHANNEL DIFFERENTIAL LINE DRIVER
Rev C1, Page 8/11
EXAMPLE 2: Long lines
Lines which are relatively long, for example 100m, require a higher driver current and an adapter. An appropriate
30S series resistor at the driver output ensures short-circuit strength and a suitable division of the power loss to
resistor and iC. The PROG pin at VSUB selects the high driver current of 100mA. In this case the driver supply
must be channeled via VB1 and VB2.
24V
5V
C2
1µF
C1
1µF
3
6
16
VCC
VT
VB1
1
A
E1
CHAN1
A1 15 30
NA1 14 30
2
B
E2
CHAN2
A2 13 30
NA2 11 30
7
Z
E3
CHAN3
A3 10 30
NA3 9 30
iC -V X THERMAL SHUTDOWN
BIAS
VEE PROG
VSUB
VB2
4
5
12
8
L=100m, CB=100pF/m
PLC
2k
2k
2k
Fig. 2: Balanced data transmission at high capacitive load, PROG to VSUB: I(A)$ 100mA
The maximum signal frequency which is restricted by the power loss can be estimated by standardizing to the
limiting values of the example for long lines:
f_max .
20kHz × ^100pF/m × ^100m ×
CB
L
24V
2
×
413K&T_a
×
75K/W
×
2
VB
70K
R_thja
channels
(2.1)
If the slew rate is the limiting factor, the following applies for the maximum signal frequency (saturation voltages
neglected):
f_max .
100mA
4×VB×(C_L%1nF)
(2.2)
CB = Line capacitance per meter
L = Length of the line
C_L = Effective capacitance at output A to NA
VB = Supply voltage
T_a = Ambient temperature
R_thja = Thermal resistance chip/board/ambient (R_thja = R_thjb + R_thba)
The current limitation of the driver stages extends to about 300mA in the 100mA setting. By that, until the
activation of the thermal shutdown, the maximum power dissipation for each 30S series resistance and for the
iC at 24V can be estimated.
Max. power loss in the resistor:
Max. power loss in the iC pro channel:
Pmax_R= I² × R = (300mA)² × 30S = 2.7W
Pmax_IC= (VB - I(A) × R) × I(A) = 4.5W