Datasheet

LTC2870/LTC2871
1
28701fb
For more information www.linear.com/LTC2870
Typical applicaTions
DescripTion
RS232/RS485 Multiprotocol
Transceivers with
Integrated Termination
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.
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.
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.
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.
Protocol Switching with
Automatic Termination Selection
FeaTures
applicaTions
n
One RS485 and Two RS232 Transceivers
n
3V to 5.5V Supply Voltage
n
20Mbps RS485 and 500kbps RS232
n
Automatic Selection of Integrated RS485 (120Ω)
and RS232 (5kΩ)Termination Resistors
n
Half-/Full-Duplex RS485 Switching
n
High ESD: ±26kV (LTC2870), ±16kV (LTC2871)
n
Logic Loopback Mode
n
1.7V to 5.5V Logic Interface
n
Supports Up to 256 RS485 Nodes
n
RS485 Receiver Failsafe Eliminates UART Lockup
n
H-Grade Available for the LTC2870 (–40°C to 125°C)
n
Available in 28-Pin 4mm × 5mm QFN and
TSSOP (LTC2870), and 38-Pin 5mm × 7mm QFN
and TSSOP (LTC2871)
n
Software Selectable RS232/RS485/RS422 Interface
n
Point-of-Sale Terminals
n
Cable Repeaters
n
Protocol Translators
Simultaneous Protocols and
RS485 Termination Switching
RS485 Duplex Switching
28701 TA01
LTC2870
1.7V TO V
CC
3V TO 5.5V 1.7V TO V
CC
3V TO 5.5V 1.7V TO V
CC
3V TO 5.5V
RS485
TERMINATION
RS485
DUPLEX
485/232
DY
Y
Z
A
B
DZ
RA
RB
Y
Z
A
B
DI
TE485
RO
DIN1
ROUT2
DIN2
ROUT1
DOUT1
RIN2
DOUT2
RIN1
LTC2871
120Ω
120Ω
Y
Z
A
B
DI,
DY
RO,
RA
H/F
LTC2870,
LTC2871
HALFFULL
RS485RS232
ON
OFF
V
DD
V
EE
GND
1µF1µF
CAP SW
2.2µF0.1µF
V
L
V
CC
220nF
10µH
V
DD
V
EE
GND
1µF1µF
CAP SW
2.2µF0.1µF
V
L
V
CC
220nF
10µH
V
DD
V
EE
GND
1µF1µF
CAP SW
2.2µF0.1µF
V
L
V
CC
220nF
10µH
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Summary of content (42 pages)