LTC1387
Single 5V RS232/RS485
Multiprotocol Transceiver
FEATURES
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DESCRIPTIO
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Two RS232 Transceivers or One RS485 Transceiver
Operates from a Single 5V Supply
Guaranteed Receiver Output with Inputs
Floating or Shorted to Ground
Logic Selectable Fast/Slow RS485 Driver Slew Rate
Low Supply Current: 7mA Typical
5µA Supply Current in Shutdown
Self-Testing Capability in Loopback Mode
Separate Driver and Receiver Enable Controls
Driver Maintains High Impedance in Three-State,
Shutdown or with Power Off
Receiver Inputs Can Withstand
±25V
The LTC
®
1387 is a low power reconfigurable CMOS bidi-
rectional transceiver. It can be configured as an RS485
differential port or as two RS232 single-ended ports. An
onboard charge pump uses four 0.1µF capacitors to
generate boosted positive and negative supplies, allowing
the RS232 drivers to meet
±5V
output swing require-
ments with only a single 5V supply. A shutdown mode
reduces the I
CC
supply current to 5µA.
The RS232 transceivers are in full compliance with RS232
specification. The RS485 transceiver is in full compliance
with RS485 and RS422 specifications. The RS485 re-
ceiver assumes a known output state when the inputs are
floating or shorted to ground. All interface drivers feature
short-circuit and thermal shutdown protection. An enable
pin allows RS485 driver outputs to be forced into high
impedance which is maintained even when the outputs are
forced beyond supply rails or the power is off. A loop back
mode allows the driver outputs to be connected back to the
receiver inputs for diagnostic self-test.
The LTC1387 is available in 20-pin plastic SSOP and SW
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIONS
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Point-of-Sale Terminals
Software Selectable Multiprotocol Interface Ports
Low Power RS485/RS422/RS232/EIA562 Interface
Cable Repeaters
Level Translators
TYPICAL APPLICATI
2
3
1 20
LTC1387
19
V
CC1
5V
18
RECOUT
17
4
5
120Ω
6
7
8
13
10
RS485 INTERFACE
120Ω
4
5
6
7
8
13
10
DR IN
SLEW
DR ENABLE
5V
15
14
9
12
11
4000-FT 24-GAUGE TWISTED PAIR
5V
5V
5V
5V
ALL CAPACITORS: 0.1µF MONOLITHIC CERAMIC TYPE
LTC1387 • TA01
U
19
20 1
LTC1387
2
3
18
V
CC2
5V
17
RECOUT
15
14
9
12
11
DR IN
SLEW
DR ENABLE
5V
UO
U
1
LINER [ LINEAR TECHNOLOGY ]
