IC-VX Datasheet, PDF (7/11 Pages) IC-Haus GmbH – 3-CHANNEL DIFFERENTIAL LINE DRIVER

iC-VX
3-CHANNEL DIFFERENTIAL LINE DRIVER
Rev C1, Page 7/11
EXAMPLE 1: Short lines
Short lines of 5m, for example, are approximations of capacitive load for the iC; no adjustment of characteristic
impedance is required. With each switching slope changeover losses of Pc= 1/2 VB × I(A) per channel occur in
the iC. The load capacity is reloaded with the guaranteed driver current I(A)$ 30mA. These changeover losses
determine the possible cut-off frequency, since the high chip power loss without cooling results in shutdown of
the iC. At high capacitive load the transmission rate can also be limited by the fall and rise times wich reduce the
signal strength.
24V
5V
3
6
VCC
VT
1
A
E1
CHAN1
C2
1µF
C1
1µF
16
VB1
A1 15
NA1 14
L=5m, CL=500pF
PLC
2k
A2 13
2
B
E2
2k
NA2 11
CHAN2
A3 10
7
Z
E3
2k
NA3 9
CHAN3
iC-V X THERMAL SHUTDOWN
BIAS
VEE PROG
VSUB
VB2
4
5
12
8
Fig. 1: Balanced data transmission at low capacitive load, PROG pin open: I(A)$ 30mA
As a typical application, Fig. 1 shows the transmission of the output signals of an incremental rotary encoder
(track A, track B, index pulse Z) to a programmable control (PLC). The maximum signal frequency which is
limited by the power loss can be estimated by standardizing the limiting values of the example for short lines:
f_max .
200kHz × ^500pF ×
CL
24V
2
×
413K&T_a
×
75K/W
×
2
VB
70K
R_thja
channels
(1.1)
If the slew-rate is the limiting factor, the following applies for the maximum signal frequency (saturation voltages
neglected):
f_max .
30mA
4×VB×(CL%1nF)
(1.2)
CL = Capacitive load at output A to output NA
VB = Supply voltage
T_a = Ambient temperature
R_thja = Thermal resistance chip/board/ambient (R_thja = R_thjb + R_thba)