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PDF ADM483 Data sheet ( Hoja de datos )
| Número de pieza | ADM483 | |
| Descripción | Slew-Rate Limited RS-485/RS-422 Transceiver | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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FEATURES
EIA RS-485/RS-422-compliant
Data rates up to 250 kbps
Slew-rate limited for low EMI
100 nA supply current in shutdown mode
Low power consumption (120 µA)
Up to 32 transceivers on one bus
Outputs high-z when disabled or powered off
–7 V to +12 V bus common-mode range
Thermal shutdown and short-circuit protection
Pin-compatible with MAX483
Specified over –40°C to +85°C temperature range
Available in 8-lead SOIC package
APPLICATIONS
Low power RS-485 applications
EMI sensitive systems
DTE-DCE interfaces
Industrial control
Packet switching
Local area networks
Level translators
5 V Low Power, Slew-Rate Limited
RS-485/RS-422 Transceiver
ADM483
FUNCTIONAL BLOCK DIAGRAM
VCC
ADM483
RO R
RE
DE
A
B
DI D
GND
Figure 1.
GENERAL DESCRIPTION
The ADM483 is a low power differential line transceiver suitable
for half-duplex data communication on multipoint bus trans-
mission lines. It is designed for balanced data transmission, and
complies with EIA Standards RS-485 and RS-422.The part
contains a differential line driver and a differential line receiver.
Both share the same differential pins, with either the driver or
the receiver being enabled at any given time.
The device has an input impedance of 12 kΩ, allowing up to
32 transceivers on one bus. Since only one driver should be
enabled at any time, the output of a disabled or powered-down
driver is three-stated to avoid overloading the bus. This 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 driver outputs are slew-rate limited to reduce EMI and data
errors caused by reflections from improperly terminated buses.
Excessive power dissipation caused by bus contention or by
output shorting is prevented by a thermal shutdown circuit.
The part is fully specified over the industrial temperature range,
and is available in an 8-lead SOIC package.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other 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. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
1 page  
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 3.
Parameter
VCC to GND
Digital I/O Voltage (DE, RE, DI, ROUT)
Driver Output/Receiver Input Voltage
Operating Temperature Range
Storage Temperature Range
θJA Thermal Impedance (SOIC)
Lead Temperature
Soldering (10 s)
Vapor Phase (60 s)
Infrared (15 s)
Rating
6V
–0.3 V to VCC + 0.3 V
–9 V to +14 V
–40°C to +85°C
–65°C to +125°C
110°C/W
300°C
215°C
220°C
ADM483
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. 0 | Page 5 of 16
5 Page 
APPLICATIONS
DIFFERENTIAL DATA TRANSMISSION
Differential data transmission is used to reliably transmit
data at high rates over long distances and through noisy
environments. Differential transmission nullifies the effects
of ground shifts and noise signals that appear as common-
mode voltages on the line. There are two main standards
approved by the Electronics Industries Association (EIA),
which specify the electrical characteristics of transceivers
used in differential data transmission.
The RS-422 standard specifies data rates up to 10 Mbaud
and line lengths up to 4000 ft. A single driver can drive a
transmission line with up to 10 receivers.
To achieve true multipoint communications, the RS-485
standard was defined. This standard meets or exceeds all the
requirements of RS-422, but also allows up to 32 drivers and 32
receivers to be connected to a single bus. An extended common-
mode range of –7 V to +12 V is defined. The most significant
difference between RS-422 and RS-485 is that the drivers may
be disabled, allowing up to 32 to be connected to a single line.
Only one driver should be enabled at a time, but the RS-485
standard contains additional specifications to guarantee device
safety in the event of line contention.
ADM483
Table 5. Comparison of RS-422 and RS-485 Interface Standards
Specification
RS-422
RS-485
Transmission Type
Differential Differential
Maximum Cable Length
4000 ft.
4000 ft.
Minimum Driver Output Voltage ±2 V
±1.5 V
Driver Load Impedance
100 Ω
54 Ω
Receiver Input Resistance
4 kΩ min
12 kΩ min
Receiver Input Sensitivity
±200 mV
±200 mV
Receiver Input Voltage Range
–7 V to +7 V –7 V to +12 V
Drivers/Receivers per Line
1/10
32/32
CABLE AND DATA RATE
The preferred transmission line for RS-485 communications
is a twisted pair. Twisted pair cable tends to cancel common-
mode noise and the magnetic fields generated by the current
flowing through each wire, thereby reducing the effective
inductance of the pair.
The ADM483 is designed for bidirectional data communica-
tions on multipoint transmission lines. A typical application
showing a multipoint transmission network is shown in
Figure 24. An RS-485 transmission line can have as many as
32 transceivers on the bus. Only one driver can transmit at a
particular time, but multiple receivers can be enabled simul-
taneously. As with any transmission line, it is important to
minimize reflections. This can be done by terminating the
extreme ends of the line by using resistors equal to the char-
acteristic impedance of the line. Stub lengths of the main
line should also be kept as short as possible. A properly
terminated transmission line appears purely resistive to
the driver.
ADM483
RO R
RE
DE
DI D
A
B
A
ADM483
B
A
ADM483
B
R
D
R
D
RO RE DE DI
RO RE DE DI
MAXIMUM NUMBER OF TRANSCEIVERS ON BUS: 32
Figure 24. Typical Half-Duplex RS-485 Network Topology
ADM483
AR
BD
RO
RE
DE
DI
Rev. 0 | Page 11 of 16
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ADM483.PDF ] | |
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