LTC2870/LTC2871
RS232/RS485 Multiprotocol
Transceivers with
Integrated Termination
Fea T Descrip T
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The LTC 2870/LTC2871 are robust pin-configurable mul-
One RS485 and Two RS232 Transceivers
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tiprotocol transceivers, supporting RS232, RS485, and
3V to 5.5V Supply Voltage
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RS422 protocols, operating on a single 3V to 5.5V supply.
20Mbps RS485 and 500kbps RS232
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The LTC2870 can be configured as two RS232 single-
Automatic Selection of Integrated RS485 (120)
ended transceivers or one RS485 differential transceiver
and RS232 (5k)Termination Resistors
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on shared I/O lines. The LTC2871 offers independent con-
Half-/Full-Duplex RS485 Switching
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trol of two RS232 transceivers and one RS485 transceiver,
High ESD: 26kV (LTC2870), 16kV (LTC2871)
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each on dedicated I/O lines.
Logic Loopback Mode
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1.7V to 5.5V Logic Interface
Pin-controlled integrated termination resistors allow
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Supports Up to 256 RS485 Nodes
for easy interface reconfiguration, eliminating external
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RS485 Receiver Failsafe Eliminates UART Lockup
resistors and control relays. Half-duplex switches allow
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H-Grade Available for the LTC2870 (40C to 125C)
four-wire and two-wire RS485 configurations. Loopback
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Available in 28-Pin 4mm 5mm QFN and
mode steers the driver inputs to the receiver outputs for
TSSOP (LTC2870), and 38-Pin 5mm 7mm QFN
diagnostic self-test.The RS485 receivers support up to
and TSSOP (LTC2871)
256 nodes per bus, and feature full failsafe operation for
floating, shorted or terminated inputs.
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An integrated DC/DC boost converter uses a tiny
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Software Selectable RS232/RS485/RS422 Interface
2mm1.6mm inductor and one capacitor, eliminating
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Point-of-Sale Terminals
the need for multiple supplies for driving RS232 levels.
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Cable Repeaters
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Analog
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Protocol Translators
Devices, Inc. All other trademarks are the property of their respective owners.
Typical a T
Protocol Switching with Simultaneous Protocols and RS485 Duplex Switching
Automatic Termination Selection RS485 Termination Switching
1.7V TO V 3V TO 5.5V 1.7V TO V 3V TO 5.5V 1.7V TO V 3V TO 5.5V
CC CC CC
220nF 220nF 220nF
10H 10H 10H
0.1F 2.2F 0.1F 2.2F 0.1F 2.2F
V CAP SW V V CAP SW V V CAP SW V
L CC L CC L CC
LTC2870 LTC2871 LTC2870,
485/232
TE485
RS485 LTC2871
RS232 RS485
TERMINATION
Y
DY OFF ON
120
Y Y
DI
Z DI,
Z
Z
DY
A
120
DZ
RO
RS485
B
H/F
FULL HALF
RA
DIN1 DOUT1
DUPLEX
A A
ROUT1 RIN1
RO,
B B
RA
DIN2 DOUT2
RB
ROUT2 RIN2
V V V V V V
DD EE DD EE DD EE
GND GND GND
1F 1F 1F 1F 1F 1F
28701 TA01
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For more information www.linear.com/LTC2870
ions pplica
ions pplica
ion uresLTC2870/LTC2871
(Notes 1 and 2)
a Te Maxi Mu M r a T
Input Supplies FEN, RA, RB, RO, ROUT1, ROUT2 ...0.3V to (V + 0.3V)
L
V , V ..................................................... 0.3V to 7V Differential Enabled Terminator Voltage
CC L
Generated Supplies (A-B or Y-Z) ..........................................................6V
V ................................................ V 0.3V to 7.5V Operating Temperature
DD CC
V .........................................................0.3V to 7.5V LTC2870C/LTC2871C ............................... 0C to 70C
EE
SW ........................................... 0.3V to (V + 0.3V) LTC2870I/LTC2871I .............................40C to 85C
DD
CAP ............................................. 0.3V to (V 0.3V) LTC2870H .......................................... 40C to 125C
EE
A, B, Y, Z, RIN1, RIN2, DOUT1, DOUT2 ....15V to 15V Storage Temperature Range .................. 65C to 125C
DI, DZ, DY, RXEN, DXEN, LB, H/F, TE485, RX485, Lead Temperature (Soldering, 10 sec)
DX485, RX232, DX232, DIN1, DIN2, FE package........................................................300C
485/232, CH2. .......................................... 0.3V to 7V
p in c F T
LTC2870 LTC2870
TOP VIEW
TOP VIEW
1 28 V
LB
L
2 27 V
H/F
CC
3 26 GND
TE485
28 27 26 25 24 23
4 25 A
V
EE
V 1 22
A
EE
5 24 B
RA
RA 2 21 B
6 23 V
RB
CC
RB 3 20 V
CC
7 22 Y
485/232
485/232 4 29 19 Y
29
V
8 21 GND
EE RXEN V
RXEN 5 18 GND EE
9 20 Z
DXEN
DXEN 6 17
Z
10 19 V
7 16 DY
DY V CC
CC
11 18 V
DZ 8 15 V DZ
DD DD
9 10 11 12 13 14 12 17 SW
FEN
13 16 GND
GND
14 15 V
CAP
EE
UFD PACKAGE
28-LEAD (4mm 5mm) PLASTIC QFN
FE PACKAGE
28-LEAD PLASTIC TSSOP
T = 150C, = 43C/W
JMAX JA
EXPOSED PAD (PIN 29) IS V ,
EE
T = 150C, = 30C/W
JMAX JA
MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 29) IS V ,
EE
MUST BE SOLDERED TO PCB
28701fb
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For more information www.linear.com/LTC2870
FEN
TE485
GND
H/F
CAP LB
V V
EE
L
GND V
CC
SW
GND
ion igura on
ings bsolu