a
FEATURES
Operates with +3.3 V Supply
EIA RS-422 and RS-485 Compliant Over Full CM Range
19 k 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 A 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
APPLICATIONS
Telecommunications
DTE-DCE Interface
Packet Switching
Local Area Networks
Data Concentration
Data Multiplexers
Integrated Services Digital Network (ISDN)
AppleTalk
Industrial Controls
3.3 V, Full Duplex, 840 A
20 Mbps, EIA RS-485 Transceiver
ADM3491
FUNCTIONAL BLOCK DIAGRAM
ADM3491
A
RO
RE
DE
Z
DI
D
Y
R
B
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 tem-
perature range and is available in DIP and SOIC packages
as well as a new 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 make it
ideal for power sensitive applications. It is suitable for commu-
nication on multipoint bus transmission lines.
It is intended for balanced data transmission and complies with
both EIA Standards RS-485 and RS-422. It contains a differen-
tial 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, during fault conditions, a significant temperature increase is
detected in the internal driver circuitry.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998
AD [ ANALOG DEVICES ]
