LTC2872 Datasheet, PDF (1/28 Pages) –

LTC2872
RS232/RS485 Dual
Multiprotocol Transceiver
with Integrated Termination
Features
n _{Four RS232 and Two RS485 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 _{Logic Loopback Mode}
n _{High ESD: ±16kV on Line I/O}
n _{1.7V to 5.5V Logic Interface}
n _{Supports Up to 256 RS485 Nodes}
n _{RS485 Receiver Full Failsafe Eliminates UART Lockup}
n _{Available in 38-Pin 5mm × 7mm QFN Package}
Applications
n _{Flexible RS232/RS485/RS422 Interface}
n _{Software Selectable Multiprotocol Interface Ports}
n _{Point-of-Sale Terminals}
n _{Cable Repeaters}
n _{Protocol Translators}
n _{PROFIBUS-DP Networks}
Description
The LTC^®2872 is a robust pin-configurable transceiver
that supports RS232, RS485, and RS422 standards while
operating on a single 3V to 5.5V supply. The LTC2872 can
be configured as four RS232 single-ended transceivers
or two RS485 differential transceivers, or combinations
of both, on shared 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 small induc-
tor and one capacitor, eliminating the need for multiple
supplies for driving RS232 levels.
L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical Applications
RS485 Mode with Duplex Control
1.7V TO V_CC
470nF
3V TO 5.5V
22µH
2.2µF
RS485
FULL HALF
DUPLEX
V_L CAP SW
H/F
LTC2872
DY1
V_CC
Y1
Z1
2.2µF
A1
RA1
B1
Y2
DY2
Z2
RA2
V_DD
2.2µF
A2
B2
V_EE
2.2µF
2.2µF
RS232 Mode
1.7V TO V_CC
470nF
3V TO 5.5V
22µH
V_L CAP SW
LTC2872
DY1
V_CC
Y1
DZ1
Z1
RA1
A1
RB1
B1
DY2
Y2
Mixed Mode with RS485 Termination
1.7V TO V_CC
470nF
3V TO 5.5V
22µH
2.2µF 2.2µF
RS485
OFF ON
TERMINATION
V_L CAP SW
LTC2872
TE485-1
DY1
RA1
V_CC
Y1
120Ω
Z1
A1
120Ω
B1
2.2µF
DY2
Y2
DZ2
Z2
RA2
A2
DZ2
Z2
RA2
A2
RB2
V_DD
2.2µF
B2
RB2
V_EE
V_DD
2.2µF 2.2µF
B2
V_EE
2872 TA01
2.2µF
2872f
1