3.3 V, Full-Duplex, 840 µA,
20 Mbps, EIA RS-485 Transceiver
ADM3491
FEATURES
Operates with 3.3 V supply
EIA RS-422 and RS-485 compliant over full CM range
19 kΩ input impedance
Up to 50 transceivers on bus
20 Mbps data rate
Short circuit protection
Specified over full temperature range
Thermal shutdown
Interoperable with 5 V logic
840 µA supply current
2 nA shutdown current
Also available in TSSOP package
Meets IEC1000-4-4 (>1 kV)
8 ns skew
Upgrade for MAX 3491, SN75ALS180
FUNCTIONAL BLOCK DIAGRAM
ADM3491
A
RO
R
B
RE
DE
Z
DI
D
Y
05234-001
Figure 1.
APPLICATIONS
Telecommunications
DTE–DCE interface
Packet switching
Local area networks
Data concentration
Data multiplexers
Integrated services digital network (ISDN)
AppleTalk
Industrial controls
The ADM3491 is intended for balanced data transmission and
complies with both EIA Standards RS-485 and RS-422. It
contains a differential line driver and a differential line receiver,
making it suitable for full-duplex data transfer.
The input impedance is 19 kΩ, allowing up to 50 transceivers to
be connected on the bus. Excessive power dissipation caused by
bus contention or by output shorting is prevented by a thermal
shutdown circuit. This feature forces the driver output into a
high impedance state, if a significant temperature increase is
detected in the internal driver circuitry during fault conditions.
The receiver contains a fail-safe feature that results in a logic
high output state, if the inputs are unconnected (floating).
The ADM3491 is fabricated on BiCMOS, an advanced mixed
technology process combining low power CMOS with fast
switching bipolar technology.
The ADM3491 is fully specified over the industrial temperature
range and is available in DIP and SOIC packages, as well as the
space-saving TSSOP package.
GENERAL DESCRIPTION
The ADM3491 is a low power, differential line transceiver
designed to operate using a single 3.3 V power supply. Low
power consumption, coupled with a shutdown mode, makes it
ideal for power-sensitive applications. It is suitable for commu-
nication on multipoint bus transmission lines.
Rev. A
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© 2004 Analog Devices, Inc. All rights reserved.
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