Preliminary Technical Data
FEATURES
High Speed Isolated RS-485 Transceiver
with Integrated Transformer Driver
ADM2485
GENERAL DESCRIPTION
The ADM2485 differential bus transceiver is an integrated,
galvanically isolated component designed for bidirectional data
communication on multipoint bus transmission lines. It is
designed for balanced transmission lines and complies with
ANSI TIA/EIA RS-485-A-1998 and ISO 8482:1987(E).
The device employs Analog Devices’
iCoupler
technology to
combine a 3-channel isolator, a 3-state differential line driver,
and a differential input receiver into a single package. An on-
chip oscillator outputs a pair of square waveforms which drive
an external transformer to provide isolated power with an
external transformer. The logic side of the device can be
powered with either a 5 V or a 3 V supply while the bus side is
powered with an isolated 5 V supply.
The ADM2485 driver has an active high enable. The driver
differential outputs and the receiver differential inputs are
connected internally to form a differential input/output port
that imposes minimal loading on the bus when the driver is
disabled or when V
DD1
or V
DD2
= 0 V. Also provided is an active
high receiver disable that causes the receive output to enter a
high impedance state.
The device has current-limiting and thermal shutdown features
to protect against output short circuits and situations where bus
contention might cause excessive power dissipation. The part is
fully specified over the industrial temperature range and is
available in a 16-lead wide-body SOIC package.
Half-duplex isolated RS-485 transceiver
Integrated oscillator driver for external transformer
PROFIBUS compliant
Complies with ANSI TIA/EIA RS-485-A-1998 and
ISO 8482:1987(E)
16 Mbps data rate
5 V or 3 V operation (V
DD1
)
50 nodes on bus
Receiver open-circuit, fail-safe design
High common-mode transient immunity: >25 kV/μs
Isolated DE OUT status output
Thermal shutdown protection
Safety and regulatory approvals (pending):
UL recognition—2500 V
RMS
for 1 minute per UL 1577
CSA component acceptance notice #5A
VDE certificate of conformity
DIN EN 60747-5-2 (VDE 0884 Part 2): 2003-01
DIN EN 60950 (VDE 0805):2001-12; EN 60950: 2000
V
IORM
= 560 V peak
Operating temperature range: -40° to 85°C
Wide body 16-lead SOIC package
APPLICATIONS
Isolated RS-485/RS-422 interfaces
PROFIBUS networks
Industrial field networks
Multipoint data transmission systems
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Figure 1
Rev.PrK
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