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LT1780/LT1781
Low Power 5V RS232
Dual Driver/Receiver with
±15kV ESD Protection
TransZorb is a registered trademark of General Instruments, GSI.
R
Output Waveforms
1780/81 TA02
DRIVER
OUTPUT
RL = 3k
CL = 2500pF
RECEIVER
OUTPUT
CL = 50pF
INPUT
0.1
F
0.1
F
0.1
F
0.1
F
LOGIC
INPUTS
LOGIC
OUTPUTS
ON/OFF
18
10
13
11
12
6
5
4
2
16
9
14
8
15
7
3
17
5V INPUT
V+ OUT
V – OUT
RS232 OUTPUT
RS232 INPUT
1780/81 TA01
5k
LT1780
U
A
O
PPLICATI
TYPICAL
S
FEATURE
D
U
ESCRIPTIO
The LT
1780/LT1781 are dual RS232 driver/receiver pairs
with integral charge pump to generate RS232 voltage
levels from a single 5V supply. Using only 0.1
F external
capacitors, these circuits consume only 40mW of power,
and can operate to 120kbaud even while driving heavy
capacitive loads. New ESD structures on the chip allow the
LT1780/LT1781 to survive
±15kV air gap and ±8kV con-
tact ESD tests per IEC 1000-4-2, eliminating the need for
costly TransZorbs
on the RS232 line pins. The LT1780/
LT1781 are fully compliant with EIA RS232 standards.
Driver outputs are protected from overload, and can be
shorted to ground or up to
±30V without damage. During
SHUTDOWN or power-off conditions, driver and receiver
outputs are in a high impedance state, allowing line
sharing.
The LT1780/LT1781 are direct upgrades to the LT1180A/
LT1181A, LT1280A/LT1281A and LT1381 for applications
which require the utmost ESD protection.
The LT1781 is available in 16-pin DIP,SO and SW pack-
ages. The LT1780 is supplied in 18-pin DIP and SW
packages for applications which require SHUTDOWN.
s
10mA Max Supply Current
s
ESD Protection to IEC 1000-4-2 Level 4
±15kV Air Gap, ±8kV Contact
s
Uses Small Capacitors: 0.1
F
s
120kBaud Operation for RL = 3k, CL = 2500pF
s
250kBaud Operation for RL = 3k, CL = 1000pF
s
Outputs Withstand
±30V Without Damage
s
CMOS Comparable Low Power: 40mW
s
Operates from a Single 5V Supply
s
Rugged Bipolar Design
s
Outputs Assume a High Impedance State When Off
or Powered Down
s
Meets All RS232 Specifications
s
Available With or Without Shutdown
s
Absolutely No Latch-up
s
Portable Computers
s
Battery-Powered Systems
s
Power Supply Generator
s
Terminals
s
Modems
U
S
A
O
PPLICATI
, LTC and LT are registered trademarks of Linear Technology Corporation.