1
LTC1318
Single 5V
RS232/RS422/AppleTalk
®
DCE Transceiver
DESCRIPTION
U
n
Dual-Mode RS232/RS422 Peripherals
n
AppleTalk

Peripherals
n
Single 5V Systems
APPLICATIONS
U
The LTC
®
1318 is a single 5V, RS232/RS422 transceiver
for connection to the DCE, or peripheral side of an interface
link. It includes an on-board charge pump to generate a
±8V supply which allows true RS232 output swings. The
charge pump requires only four external 0.1µF capacitors.
The LTC1318 includes two RS232 drivers, a differential
RS422 driver, a dedicated RS232 receiver, and a pin
selectable RS232/RS422 receiver which can receive either
single-ended or differential signals.
The LTC1318 features driver outputs which can be taken
to common-mode voltages outside the power supply rails
without damage. Additionally, the driver outputs assume
a high impedance state when the power is shut off,
preventing externally applied signals from feeding back
into the power supplies. The RS232 devices will operate at
speeds up to 100kbaud. The RS422 devices will operate
up to 2Mbaud.
The LTC1318 is available in a 24-lead SO Wide package.
n
Single Chip Provides DCE RS232 or
RS422/AppleTalk

DCE Port
n
Operates from a Single 5V Supply
n
Charge Pump Uses 0.1µF Capacitors
n
Output Common-Mode Voltage Range Exceeds
Power Supply Rails for All Drivers
n
Driver Outputs Are High Impedance with Power Off
n
Pin Selectable RS232/RS422 Receiver
n
Thermal Shutdown Protection
n
Drivers Are Short-Circuit Protected
FEATURES
, LTC and LT are registered trademarks of Linear Technology Corporation.
AppleTalk and LocalTalk are registered trademarks of Apple Computer, Inc.
TYPICAL APPLICATIONS
U
CHARGE
PUMP
RS232
LINES
APPLETALK
NETWORK
LOCALTALK
®

TRANSFORMER
100pF × 4
22Ω
22Ω
22Ω
22Ω
22Ω
22Ω
22Ω
22Ω
V
+

C1
+

C1
–

RXI1
TXO1
TXO2
V
CC

RXD
+

RXD
–
/RXI2
TXD
+

TXD
–

NC
V
–

C2
–

C2
+

RXO1
TXI1
TXI2
GND
RXDO/RXO2
TXD
RXMODE
GND
NC
0.1µF0.1µF
0.1µF
RS232
RS232
RS232
RS422
RS422
5V
1k
1k
0.1µF
LTC1318
TO
DIGITAL
SYSTEM
LT1318 • TA01
RS232
R
L
= 100Ω 200ns/DIV 1318 TA02
C
L
= 100pF
Driver Output Waveforms
TXD
(5V/DIV)
TXD
+
, TXD
–
(2V/DIV)
RXDO
(5V/DIV)