LT1237
5V RS232 Transceiver with
Advanced Power Management and
One Receiver Active in Shutdown
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FEATURES
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DESCRIPTIO
One Receiver Remains Active While in Shutdown
ESD Protection over ±15kV
Uses Small Capacitors: 0.1µF, 0.2µF, 1.0µF
60µA Supply Current in Shutdown
Pin Compatible with LT1137A
120kBaud Operation for RL = 3k, CL = 2500pF
250kBaud Operation for RL = 3k, CL = 1000pF
Operates to 120kBaud
CMOS Comparable Low Power 30mW
Operates from a Single 5V Supply
Easy PC Layout—Flowthrough Architecture
Rugged Bipolar Design
Outputs Assume a High Impedance State When Off
or Powered Down
Absolutely No Latchup
Available in SO and SSOP Packages
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APPLICATIO S
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The LT®1237 is an advanced low power three driver, five
receiver RS232 transceiver. Included on the chip is a
shutdown pin for reducing supply current near zero.
During shutdown one receiver remains active to detect
incoming RS232 signals, for example, to wake up a
system.
The LT1237 is fully compliant with all EIA RS232 specifications. New ESD structures on the chip allow the LT1237
to survive multiple ±15kV strikes, eliminating the need for
costly TransZorbs® on the RS232 line pins.
The LT1237 operates in excess of 120kbaud even driving
heavy capacitive loads. Two shutdown modes allow the
driver outputs to be shut down separately from the receivers for more versatile control of the RS232 interface.
During shutdown, drivers and receivers assume a high
impedance state.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TransZorb is a registered trademark of General Instruments, GSI
Notebook Computers
Palmtop Computers
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TYPICAL APPLICATIO
Output Waveforms
V+
1.0µF
5V VCC
1
2
28
LT1237
3
DRIVER 1 OUT
RX1 IN
DRIVER 2 OUT
TO
LINE
RX2 IN
RX3 IN
RX4 IN
DRIVER 3 OUT
RX5 IN (LOW-Q)
ON/OFF
25
5
24
6
23
7
22
8
21
9
20
10
19
11
18
12
17
13
16
14
15
0.1µF
RECEIVER
OUTPUT
CL = 50pF
2 × 0.1µF
26
4
2 × 0.1µF
V–
27
DRIVER 1 IN
RX1 OUT
DRIVER 2 IN
RX2 OUT
TO LOGIC
R
DRIVER
OUTPUT
RL = 3k
CL = 2500pF
RX3 OUT
RX4 OUT
DRIVER 3 IN
RX5 OUT (LOW-Q)
GND
DRIVER
DISABLE
INPUT
RING DETECT IN
µCONTROLLER OR
µPROCESSOR
1237 TA02
SHUTDOWN
CONTROL OUT
LT1237 TA01
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