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PDF ADM489 Data sheet ( Hoja de datos )
| Número de pieza | ADM489 | |
| Descripción | EIA RS-485 Transceivers | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Full-Duplex, Low Power,
Slew Rate Limited, EIA RS-485 Transceivers
ADM488/ADM489
FEATURES
Meets EIA RS-485 and RS-422 standards
250 kbps data rate
Single 5 V ± 10% supply
−7 V to +12 V bus common-mode range
12 kΩ input impedance
2 kV EFT protection meets IEC1000-4-4
High EM immunity meets IEC1000-4-3
Reduced slew rate for low EM interference
Short-circuit protection
Excellent noise immunity
30 μA supply current
APPLICATIONS
Low power RS-485 and RS-422 systems
DTE-DCE interface
Packet switching
Local area networks
Data concentration
Data multiplexers
Integrated services digital network (ISDN)
GENERAL DESCRIPTION
The ADM488 and ADM489 are low power, differential line
transceivers suitable for communication on multipoint bus
transmission lines. They are intended for balanced data
transmission and comply with both Electronics Industries
Association (EIA) RS-485 and RS-422 standards. Both products
contain a single differential line driver and a single differential
line receiver, making them suitable for full-duplex data transfer.
The ADM489 contains an additional receiver and driver enable
control.
The input impedance is 12 kΩ, allowing 32 transceivers to be
connected on the bus.
The ADM488/ADM489 operate from a single 5 V ± 10% power
supply. Excessive power dissipation caused by bus contention or
output shorting is prevented by a thermal shutdown circuit.
This feature forces the driver output into a high impedance state
if, during fault conditions, a significant temperature increase is
detected in the internal driver circuitry.
FUNCTIONAL BLOCK DIAGRAMS
ADM488
A
RO R
B
DI D
Z
Y
Figure 1.
ADM489
A
RO R
B
RE
DE
DI D
Z
Y
Figure 2.
The receiver contains a fail-safe feature that results in a logic
high output state if the inputs are unconnected (floating).
The ADM488/ADM489 are fabricated on BiCMOS, an
advanced mixed technology process combining low power
CMOS with fast switching bipolar technology.
The ADM488/ADM489 are fully specified over the industrial
temperature range and are available in PDIP, SOIC, and TSSOP
packages.
Rev. D
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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.
1 page  
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 3.
Parameter
VCC
Inputs
Driver Input (DI)
Control Inputs (DE, RE)
Receiver Inputs (A, B)
Outputs
Driver Outputs
Receiver Output
Power Dissipation 8-Lead PDIP
θJA, Thermal Impedance
Power Dissipation 8-Lead SOIC
θJA, Thermal Impedance
Power Dissipation 14-Lead PDIP
θJA, Thermal Impedance
Power Dissipation 14-Lead SOIC
θJA, Thermal Impedance
Power Dissipation 16-Lead TSSOP
θJA, Thermal Impedance
Operating Temperature Range
Industrial (A Version)
Storage Temperature Range
Lead Temperature (Soldering, 10 sec)
Vapor Phase (60 sec)
Infrared (15 sec)
ESD Association S5.1 HBM Standard
EFT Rating, IEC1000-4-4
Rating
7V
−0.3 V to VCC + 0.3 V
−0.3 V to VCC + 0.3 V
−14 V to +14 V
−14 V to +12.5 V
−0.5 V to VCC + 0.5 V
700 mW
120°C/W
520 mW
110°C/W
800 mW
140°C/W
800 mW
120°C/W
800 mW
150°C/W
−40°C to +85°C
−65°C to +150°C
300°C
215°C
220°C
3 kV
2 kV
ADM488/ADM489
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. D | Page 5 of 16
5 Page 
ADM488/ADM489
THEORY OF OPERATION
The ADM488/ADM489 are ruggedized RS-485 transceivers
that operate from a single 5 V supply. They contain protection
against radiated and conducted interference and are ideally
suited for operation in electrically harsh environments or where
cables can be plugged/unplugged. They are also immune to
high RF field strengths without special shielding precautions.
They are intended for balanced data transmission and comply
with both EIA RS-485 and RS-422 standards. They contain a
differential line driver and a differential line receiver, and are
suitable for full-duplex data transmission.
The input impedance on the ADM488/ADM489 is 12 kΩ,
allowing up to 32 transceivers on the differential bus. The
ADM488/ADM489 operate from a single 5 V ± 10% power
supply. A thermal shutdown circuit prevents excessive power
dissipation caused by bus contention or by output shorting.
This feature forces the driver output into a high impedance state
if, during fault conditions, a significant temperature increase is
detected in the internal driver circuitry.
The receiver contains a fail-safe feature that results in a logic
high output state if the inputs are unconnected (floating). A
high level of robustness is achieved using internal protection
circuitry, eliminating the need for external protection com-
ponents such as tranzorbs or surge suppressors. Furthermore,
low electromagnetic emissions are achieved using slew limited
drivers, minimizing interference both conducted and radiated.
The ADM488/ADM489 can transmit at data rates up to
250 kbps. A typical application for the ADM488/ADM489 is
illustrated in Figure 24 showing a full-duplex link where data is
transferred at rates of up to 250 kbps. A terminating resistor is
shown at both ends of the link. This termination is not critical
because the slew rate is controlled by the ADM488/ADM489
and reflections are minimized.
5V 5V
0.1µF
0.1µF
VCC
RE
RO R
A
B
ADM488
DI D
DE
GND
Z
Y
RS-485/RS-422 LINK
VCC DE
Y
Z D DI
ADM489
B
A R RO
RE
GND
Figure 24. ADM488/ADM489 Full-Duplex Data Link
The communications network can be extended to include
multipoint connections, as shown in Figure 30. As many as
32 transceivers can be connected to the bus.
Table 6 and Table 7 show the truth tables for transmitting and
receiving.
Table 6. Transmitting Truth Table
Inputs
RE DE DI
X1 1 1
X1 1 0
0 0 X1
1 0 X1
Outputs
ZY
01
10
Hi-Z Hi-Z
Hi-Z Hi-Z
1 X = Don’t care.
Table 7. Receiving Truth Table
Inputs
RE DE
A to B
00
≥ +0.2 V
00
≤ −0.2 V
00
10
Inputs O/C
X1
Output
RO
1
0
1
Hi-Z
1 X = Don’t care.
EFT TRANSIENT PROTECTION SCHEME
The ADM488/ADM489 use protective clamping structures on
their inputs and outputs that clamp the voltage to a safe level
and dissipate the energy present in ESD (electrostatic) and EFT
(electrical fast transients) discharges.
FAST TRANSIENT BURST IMMUNITY (IEC1000-4-4)
IEC1000-4-4 (previously 801-4) covers electrical fast transient
burst (EFT) immunity. Electrical fast transients occur as a result
of arcing contacts in switches and relays. The tests simulate the
interference generated when, for example, a power relay disconnects
an inductive load. A spark is generated due to the well known
back EMF effect. In fact, the spark consists of a burst of sparks
as the relay contacts separate. The voltage appearing on the line,
therefore, consists of a burst of extremely fast transient impulses.
A similar effect occurs when switching on fluorescent lights.
The fast transient burst test, defined in IEC1000-4-4, simulates
this arcing, and its waveform is illustrated in Figure 25. It
consists of a burst of 2.5 kHz to 5 kHz transients repeating at
300 ms intervals. It is specified for both power and data lines.
Four severity levels are defined in terms of an open-circuit voltage
as a function of installation environment. The installation
environments are defined as
• Well protected
• Protected
• Typical industrial
• Severe industrial
Rev. D | Page 11 of 16
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ADM489.PDF ] | |
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