LT1331
3V RS562 or 5V/3V RS232
Transceiver with One Receiver
Active in Shutdown
FEATURES
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DESCRIPTIO
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RS232 Compatible 3V Operation
3V Logic Interface
ESD Protection Over
±10kV
120kbaud Operation for R
L
= 3k, C
L
= 2500pF
250kbaud Operation for R
L
= 3k, C
L
= 1000pF
One Low Power Receiver Remains Active While
in Shutdown
60µA Supply Current in Shutdown
Low Power Driver Disable Mode
Uses Small Capacitors: 0.1µF, 0.2µF
CMOS Comparable Low Power: 60mW
Easy PC Layout: Flowthrough Architecture
Rugged Bipolar Design
Outputs Assume a High Impedance State When
Off or Powered Down
The LT
®
1331 is a 3-driver, 5-receiver RS232 transceiver
designed for 3V and mixed 3V/5V systems. Receivers
operate from 3V logic supply V
L
, while the onboard charge
pump and drivers operate from 5V or 3V supply V
CC
.
The transceiver has two shutdown modes. One mode
disables the drivers and the charge pump, the other shuts
down all circuitry except for one low power receiver which
can be used for ring detection. The V
CC
supply may be shut
down while in ring detection mode. While shut down, the
drivers and receivers assume high impedance output
states.
The LT1331 is fully compliant with all EIA-RS232 specifi-
cations when V
CC
= 5V. If V
CC
= 3V, output drive levels are
compatible with all known interface circuits. Special bipo-
lar construction techniques protect the drivers and receiv-
ers beyond the fault conditions stipulated for RS232. The
RS232 I/O pins are resilient to multiple
±10kV
ESD strikes.
An advanced driver output stage operates up to 120kbaud
while driving heavy capacitive loads.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
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Notebook Computers
Palmtop Computers
TYPICAL APPLICATI
+
0.1µF
2
×
0.1µF
V
+
1
2
3
4
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
3.3V V
L
5
6
7
8
9
10
11
12
13
14
LT1331
V
CC
= 3.3V
3.3V Operation
28 V
–
27
25
24
23
22
21
20
19
0.1µF
26
DRIVER 1 IN
RX1 OUT
DRIVER 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
INPUT
R
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
RECEIVER
OUTPUT
C
L
= 50pF
DRIVER 3 IN
18 RX5 OUT (LOW-Q)
17
GND
16
DRIVER DISABLE
15
NC
+
+
TO LOGIC
RING DETECT IN
µCONTROLLER
OR
µPROCESSOR
SHUTDOWN
CONTROL OUT
1331 TA01
1331 TA02
+
2
×
0.1µF
U
UO
UO
1
LINER [ LINEAR TECHNOLOGY ]
