Data Sheet
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
Available in PDIP, SOIC, and TSSOP
Meets IEC1000-4-4 (>1 kV)
8 ns skew
Upgrade for MAX3491, SN75ALS180
3.3 V, Full-Duplex, 840 μA,
20 Mbps, EIA RS-485 Transceiver
FUNCTIONAL BLOCK DIAGRAM
ADM3491-1
A
RO
RE
DE
Z
DI
D
Y
05234-001
R
B
Figure 1.
APPLICATIONS
Telecommunications
DTE–DCE interface
Packet switching
Local area networks
Data concentration
Data multiplexers
Integrated services digital network (ISDN)
AppleTalk
Industrial controls
GENERAL DESCRIPTION
The
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.
The
is intended for balanced data transmission
and complies with both Electronic Industries Association (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. A thermal shutdown circuit prevents
excessive power dissipation caused by bus contention or by
output shorting. 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.
If the inputs are unconnected (floating), the receiver contains a
fail-safe feature that results in a logic high output state.
The
is fabricated on BiCMOS, an advanced mixed
technology process combining low power CMOS with fast
switching bipolar technology.
Rev. C
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