5 V, 0.8 mA PROFIBUS
RS-485 Transceiver
ADM1486
Rev. A
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FEATURES
Meets and exceeds EIA RS-485 and EIA RS-422 standards
30 Mbps data rate
Recommended for PROFIBUS applications
2.1 V minimum differential output with 54 Ω termination
Low power 0.8 mA I
CC
Thermal shutdown and short-circuit protection
0.5 ns skew driver and receiver
Driver propagation delay: 11 ns
Receiver propagation delay: 12 ns
High impedance outputs with drivers disabled or power off
Superior upgrade for SN65ALS1176
Available in standard 8-lead SOIC package
APPLICATIONS
Industrial field equipment
GENERAL DESCRIPTION
The ADM1486 is a differential line transceiver suitable for high
speed bidirectional data communication on multipoint bus
transmission lines. It is designed for balanced data transmission,
complies with EIA Standards RS-485 and RS-422, and is recom-
mended for PROFIBUS applications. The part contains a
differential line driver and a differential line receiver. Both the
driver and the receiver may be enabled independently. When
disabled or powered down, the driver outputs are high impedance.
The ADM1486 operates from a single 5 V power supply.
Excessive power dissipation caused by bus contention or output
shorting is prevented by short-circuit protection and thermal
circuitry. Short-circuit protection circuits limit the maximum
output current to ±200 mA during fault conditions. A thermal
shutdown circuit senses if the die temperature rises above
150°C and forces the driver outputs into a high impedance state
under this condition.
Up to 50 transceivers may be connected simultaneously on a
bus, but only one driver should be enabled at a time. Therefore,
it is important that the remaining disabled drivers do not load
the bus.
FUNCTIONAL BLOCK DIAGRAM
ADM1486
R
D
RO
RE
DE
DI
V
CC
B
A
GND
8
5
6
7
1
4
3
2
02603-001
Figure 1.
To ensure this, the ADM1486 driver features high output
impedance when disabled and when powered down. This
minimizes the loading effect when the transceiver is not being
used. The high impedance driver output is maintained over the
entire common-mode voltage range from −7 V to +12 V.
The receiver contains a fail-safe feature that results in a logic
high output state if the inputs are unconnected (floating).
The ADM1486 is fabricated on BiCMOS, an advanced mixed
technology process combining low power CMOS with fast
switching bipolar technology. All inputs and outputs contain
protection against ESD; all driver outputs feature high source
and sink current capability. An epitaxial layer is used to guard
against latch-up.
The ADM1486 features extremely fast and closely matched
switching, enable, and disable times. Minimal driver propaga-
tion delays permit transmission at data rates up to 30 Mbps
while low skew minimizes EMI interference.
The part is fully specified over the commercial and industrial
temperature range and is available in an 8-lead SOIC package.
