LTC2870_15 Datasheet, PDF (1/42 Pages) Linear Technology – RS232/RS485 Multiprotocol Transceivers with Integrated Termination

Features
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 (–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)
Applications
n _{Software Selectable RS232/RS485/RS422 Interface}
n _{Point-of-Sale Terminals}
n _{Cable Repeaters}
n _{Protocol Translators}
LTC2870/LTC2871
RS232/RS485 Multiprotocol
Transceivers with
Integrated Termination
Description
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 control 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 Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Typical Applications
Protocol Switching with
Automatic Termination Selection
1.7V TO V_{CC 220nF}
3V TO 5.5V
10µH
Simultaneous Protocols and
RS485 Termination Switching
1.7V TO V_{CC 220nF}
3V TO 5.5V
10µH
0.1µF
RS232 RS485
V_L CAP SW
LTC2870
485/232
DY
DZ
RA
RB
V_DD
1µF
GND
V_CC
Y
Z
A
B
V_EE
2.2µF
0.1µF
RS485
TERMINATION
OFF ON
1µF
1µF
V_L CAP SW
TE485
LTC2871
DI
RO
V_CC
Y
120Ω
Z
A
120Ω
B
DIN1
DOUT1
ROUT1
RIN1
DIN2
DOUT2
ROUT2
V_DD
GND
RIN2
V_EE
2.2µF
1µF
For more information www.linear.com/LTC2870
RS485 Duplex Switching
1.7V TO V_{CC 220nF}
3V TO 5.5V
10µH
0.1µF
V_L CAP SW
V_CC
LTC2870,
LTC2871
2.2µF
DI,
DY
RS485
FULL HALF ^H/F
DUPLEX
RO,
RA
V_DD
1µF
Y
Z
A
B
GND
V_EE
28701 TA01
1µF
28701fa
1