LT1080/LT1081
APPLICATIO S I FOR ATIO
The driver output stage of the LT1080 offers significantly
improved protection over older bipolar and CMOS de-
signs. In addition to current limiting, the driver output can
be externally forced to
±30V
with no damage or excessive
current flow, and will not disrupt the supplies. Some
drivers have diodes connected between the outputs and
the supplies, so externally applied voltages can cause
excessive supply voltage to develop.
LT1080/LT1081 Driver
30V
–30V
OUTPUT CAN
BE FORCED
EXTERNALLY
1080/81 F01
Older RS232 Drivers and CMOS Drivers
V
+
WITH SOME DRIVERS,
EXTERNALLY APPLIED
VOLTAGE CAN FORCE
THE SUPPLIES
V
–
1080/81 F02
Sharing a Receiver Line
LT1080 #1
RECEIVER
RS232
INPUT A
LOGIC
INPUT A
LT1080 #2
RECEIVER
RS232
INPUT B
LOGIC
OUTPUT
LOGIC
INPUT B
ON/OFF
(CHANNEL
SELECT)
INPUT
LOGIC
INVERTER
1080/81 F04
6
U
Placing the LT1080 in the SHUTDOWN mode (Pin 18 low)
puts both the driver and receiver outputs in a high imped-
ance state. This allows data line sharing and transceiver
applications.
The SHUTDOWN mode also drops input supply current
(V
CC
; Pin 17) to zero for power-conscious systems.
Transceiver
LT1080 #1
DRIVER
LOGIC
TRANSMIT/RECEIVE
LINE
RS232
TRANSMIT/RECEIVE
LINE
LT1080 #2
RECEIVER
ON/OFF
(TRANSMIT/
RECEIVE)
INPUT
LOGIC
INVERTER
1080/81 F03
W
U
U
Sharing a Transmitter Line
LT1080 #1
DRIVER
LT1080 #2
DRIVER
RS232
TRANSMISSION
LINE
ON/OFF
(CHANNEL
SELECT)
INPUT
LOGIC
INVERTER
1080/81 F05
LINER [ LINEAR TECHNOLOGY ]
