LT1342
5V RS232 Transceiver with
3V Logic Interface
U
DESCRIPTIO
EATURE
S
F
The LT®1342 is an advanced low power three-driver, five-
receiver RS232 transceiver. The LT1342 operates from a
5V supply and a 3V logic supply. Receiver outputs can
interface directly to 3V logic circuits. Included on the chip
isashutdownpinforreducingsupplycurrenttonearzero.
All receivers and drivers assume high impedance states
during shutdown.
■
■
■
■
■
■
■
■
■
■
■
■
■
ESD Protection Over ±10kV
3V Logic Interface
Uses Small Capacitors: 0.1µF, 0.2µF
1µA Supply Current in Shutdown
Low Power Driver Disable Operating Mode
Pin Compatible with LT1137A
120kBaud Operation for RL = 3k, CL = 2500pF
250kBaud Operation for RL = 3k, CL = 1000pF
CMOS Comparable Low Power: 60mW
Operates from a 5V Supply and 3V Logic Supply
Easy PC Layout: Flowthrough Architecture
Rugged Bipolar Design
The driver disable function provides additional control of
operating mode. When driver disable is high the charge
pump and drivers turn off. Receivers continue to operate
during driver disable.
New ESD structures on the chip allow the LT1342 to
survive multiple ±10kV strikes, eliminating the need for
costly TransZorbs® on the RS232 line pins.
Outputs Assume a High Impedance State When
Off or Powered Down
Absolutely No Latchup
■
The LT1342 is fully compliant with all EIA RS232 specifi-
cations and operates in excess of 120kbaud even driving
heavy capacitive loads.
O U
PPLICATI
S
A
■
Notebook Computers
Palmtop Computers
, LTC and LT are registered trademarks of Linear Technology Corporation.
TransZorb is a registered trademark of General Instruments, GSI.
■
U
O
TYPICAL APPLICATI
Output Waveforms
+
–
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
V
RECEIVER
OUTPUT
0.1µF
0.1µF
5V V
CC
2 × 0.1µF
V
L = 3V
3
LT1342
CL = 50pF
2 × 0.1µF
4
DRIVER 1 IN
RX1 OUT
DRIVER 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
DRIVER 3 IN
RX5 OUT
GND
5
DRIVER 1 OUT
RX1 IN
DRIVER
6
R
OUTPUT
RL = 3k
7
DRIVER 2 OUT
RX2 IN
C
L = 2500pF
TO 3V LOGIC
8
TO LINE
9
RX3 IN
10
11
12
13
14
RX4 IN
DRIVER 3 OUT
RX5 IN
INPUT
ON/OFF
DRIVER DISABLE
LT1342 • TA02
3V V
NC
L
LT1342 • TA01
1