High Speed, Isolated RS-485 Transceiver
with Integrated Transformer Driver
ADM2485
FEATURES
Half-duplex, isolated RS-485 transceiver
Integrated oscillator driver for external transformer
PROFIBUS® compliant
Complies with ANSI/TIA/EIA RS-485-A-98 and
ISO 8482:1987(E)
Data rate: 16 Mbps
5 V or 3.3 V operation (V
DD1
)
50 nodes on bus
High common-mode transient immunity: >25 kV/μs
Isolated DE OUT status output
Thermal shutdown protection
Safety and regulatory approvals
UL recognition: 2500 V rms for 1 minute per UL 1577
VDE Certificate of Conformity
DIN V VDE V 0884-10 (VDE V 0884-10):2006-12
Reinforced insulation, V
IORM
= 560 V peak
Operating temperature range: –40°C to +85°C
Wide-body, 16-lead SOIC package
FUNCTIONAL BLOCK DIAGRAM
V
DD1
D1
D2
V
DD2
OSC
GALVANIC ISOLATION
ADM2485
DE OUT
RTS
TxD
A
B
RxD
RE
GND
1
GND
2
Figure 1.
APPLICATIONS
Isolated RS-485/RS-422 interfaces
PROFIBUS networks
Industrial field networks
Multipoint data transmission systems
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-98 and ISO 8482:1987(E).
The device employs Analog Devices, Inc.,
iCoupler®
technology
to combine a 3-channel isolator, a three-state differential line
driver, and a differential input receiver into a single package. An
on-chip oscillator outputs a pair of square waveforms that 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 3.3 V supply, and 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.
Rev. A
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rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
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©2007 Analog Devices, Inc. All rights reserved.
06021-001
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