ANALOG DEVICES ADM2491E Service Manual
High Speed, ESD-Protected, Half-/Full-Duplex
i
ADM2491E
V
DD1
GND
1
A
B
V
DD2
GND
2
Y
Z
TxD
DE
RxD
ADM2491E
06985-001
GALVANIC ISOLATION
RE
FEATURES
Isolated, RS-485/RS-422 transceiver, configurable as half- or
full-duplex
±8 kV ESD protection on RS-485 input/output pins
16 Mbps data rate
Complies with ANSI TIA/EIA RS-485-A-1998 and
ISO 8482: 1987(E)
Suitable for 5 V or 3.3 V operation (V
High common-mode transient immunity: >25 kV/μs
Receiver has open-circuit, fail-safe design
32 nodes on the bus
Thermal shutdown protection
Safety and regulatory approvals
UL recognition: 5000 V rms isolation voltage
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
Operating temperature range: −40°C to +85°C
Wide body, 16-lead SOIC package
)
DD1
= 848 V peak
Coupler Isolated RS-485 Transceiver
FUNCTIONAL BLOCK DIAGRAM
Figure 1.
APPLICATIONS
Isolated RS-485/RS-422 interfaces
Industrial field networks
INTERBUS
Multipoint data transmission systems
GENERAL DESCRIPTION
The ADM2491E is an isolated data transceiver with ±8 kV ESD
protection and is suitable for high speed, half- or full-duplex
communication on multipoint transmission lines. For halfduplex operation, the transmitter outputs and the receiver
inputs share the same transmission line. Transmitter output
Pin Y is linked externally to receiver input Pin A, and transmitter output Pin Z is linked to receiver input Pin B.
The ADM2491E 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, Inc.,
iCoupler® technology to combine a 3-channel isolator, a threestate differential line driver, and a differential input receiver into
a single package.
The differential transmitter outputs and receiver inputs feature
electrostatic discharge circuitry that provides protection to
±8 kV using the human body model (HBM). The logic side of
the device can be powered with either a 5 V or a 3.3 V supply,
whereas the bus side requires an isolated 5 V supply.
The device has current-limiting and thermal shutdown features
to protect against output short circuits and situations in which
bus contention could cause excessive power dissipation.
The ADM2491E is available in a wide body, 16-lead SOIC package
and operates over the −40°C to +85°C temperature range.
Rev. B
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