iC-VX
3-CHANNEL DIFFERENTIAL LINE DRIVER
Rev C1, Page 9/11
The average power loss in the iC and the resistors declines when the thermal shutdown interrupts the driver
outputs due to abnormal rising chip temperature. The installed series resistances should suit for the estimated
power dissipation to avoid overload due to permanent line short-circuits. If the drivers are operated at low power
supply, e.g. VB= 12V instead of VB= 24V, the power loss account for the iC declines and the thermal shutdown
is initially delayed or is not activated at all. If VB is under 20V, lower resistors are permitted (>10S) without
endangering the short-circuit strength of the iC. Consequently, the iC’s temperature monitoring is reactivated and
even 1/3W resistors are not overloaded.
EXAMPLE 3:
Data transmission in the case of activation with TTL/CMOS signals
In the case of activation with TTL/CMOS logic, the device can be operated with the 5V logic supply to VCC and
VT. The pins VEE and VSUB must be connected to the logic ground. The 24V supply voltage must be applied
to VB1 or VB2 (Fig. 3).
Figure 4 shows an alternative application with common positive supplies for logic and driver. Ground,
respectively the reference potential VEE for the inputs, is generated by using a negative voltage regulator. This
wiring increases the iC power dissipation due to the higher bias supply voltage at VT.
Fig. 3: VEE = VSUB
Fig. 4: VEE > VSUB
In both examples the operating points of the Schmitt trigger inputs E1..3 are compatible with TTL and CMOS
levels.
Depending on the line length, the driver current may be selected to 30mA with PROG= open or to 100mA with
PROG= VSUB. In case of the 100mA driver current the final stages must be supplied via VB1 and VB2.
ICHAUS [ IC-HAUS GMBH ]
