LTC2870/LTC2871
RS232/RS485 Multiprotocol
Transceivers with
Integrated Termination
DescripTion
FeaTures
The LTC®2870/LTC2871 are robust pin-configurable mul-
tiprotocol transceivers, supporting RS232, RS485, and
RS422 protocols, operating on a single 3V to 5.5V supply.
The LTC2870 can be configured as two RS232 single-
ended transceivers or one RS485 differential transceiver
on shared I/O lines. The LTC2871 offers independent con-
trol of two RS232 transceivers and one RS485 transceiver,
each on dedicated I/O lines.
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One RS485 and Two RS232 Transceivers
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3V to 5.5V Supply Voltage
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20Mbps RS485 and 500kbps RS232
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Automatic Selection of Integrated RS485 (120Ω)
and RS232 (5kΩ)Termination Resistors
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Half-/Full-Duplex RS485 Switching
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High ESD: 2ꢀkV (ꢁTꢂ28ꢃ0)ꢄ 1ꢀkV (ꢁTꢂ28ꢃ1)
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Logic Loopback Mode
1.7V to 5.5V Logic Interface
Supports Up to 256 RS485 Nodes
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Pin-controlled integrated termination resistors allow
for easy interface reconfiguration, eliminating external
resistors and control relays. Half-duplex switches allow
four-wire and two-wire RS485 configurations. Loopback
mode steers the driver inputs to the receiver outputs for
diagnostic self-test.The RS485 receivers support up to
256 nodes per bus, and feature full failsafe operation for
floating, shorted or terminated inputs.
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RS485 Receiver Failsafe Eliminates UART Lockup
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H-Grade Available for the LTC2870 (–40°C to 125°C)
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Available in 28-Pin 4mm × 5mm QFN and
TSSOP (LTC2870), and 38-Pin 5mm × 7mm QFN
and TSSOP (LTC2871)
applicaTions
An integrated DC/DC boost converter uses a tiny
2mm × 1.6mm inductor and one capacitor, eliminating
the need for multiple supplies for driving RS232 levels.
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Software Selectable RS232/RS485/RS422 Interface
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Point-of-Sale Terminals
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Cable Repeaters
Protocol Translators
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Analog
Devices, Inc. All other trademarks are the property of their respective owners.
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Typical applicaTions
Protocol Switching with
Simultaneous Protocols and
RS485 Termination Switching
RS485 Duplex Switching
Automatic Termination Selection
1.7V TO V
3V TO 5.5V
10µH
1.7V TO V
3V TO 5.5V
10µH
1.7V TO V
CC
220nF
3V TO 5.5V
10µH
CC
CC
220nF
220nF
0.1µF
2.2µF
0.1µF
2.2µF
0.1µF
2.2µF
V
CAP SW
LTC2870
V
CC
V
CAP SW
LTC2871
V
CC
V
L
CAP SW
LTC2870,
LTC2871
V
CC
L
L
485/232
TE485
RS485
TERMINATION
RS232 RS485
Y
DY
OFF ON
120Ω
120Ω
Y
Y
DI
DI,
DY
Z
Z
Z
A
DZ
RA
RO
RS485
FULL HALF
DUPLEX
B
H/F
DIN1
DOUT1
RIN1
A
B
A
B
ROUT1
DIN2
RO,
RA
DOUT2
RB
ROUT2
RIN2
V
V
EE
V
DD
V
EE
V
DD
V
DD
EE
GND
GND
GND
1µF
1µF
1µF
1µF
1µF
1µF
28701 TA01
28701fb
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For more information www.linear.com/LTC2870