ADM485JR ,+5 V Low Power EIA RS-485 TransceiverSpecifications subject to change without notice.–2–REV. AADM485ABSOLUTE MAXIMUM RATINGS*PIN FUNCTIO ..
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+5 V Low Power EIA RS-485 Transceiver
FUNCTIONAL BLOCK DIAGRAMREV.A
+5 V Low Power
EIA RS-485 Transceiver
FEATURES
Meets EIA RS-485 Standard
5 Mb/s Data Rate
Single +5 V Supply
–7 V to +12 V Bus Common-Mode Range
High Speed, Low Power BiCMOS
Thermal Shutdown Protection
Short Circuit Protection
Zero Skew Driver
Driver Propagation Delay: 10 ns
Receiver Propagation Delay: 25 ns
High Z Outputs with Power Off
Superior Upgrade for LTC485
APPLICATIONS
Low Power RS-485 Systems
DTE-DCE Interface
Packet Switching
Local Area Networks
Data Concentration
Data Multiplexers
Integrated Services Digital Network (ISDN)
PRODUCT DESCRIPTIONThe ADM485 is a differential line transceiver suitable for high
speed bidirectional data communication on multipoint bus
transmission lines. It is designed for balanced data transmission
and complies with both EIA Standards RS-485 and RS-422.
The part contains a differential line driver and a differential line
receiver. Both the driver and the receiver may be enabled inde-
pendently. When disabled, the outputs are tristated.
The ADM485 operates from a single +5 V power supply.
Excessive power dissipation caused by bus contention or by out-
put 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.
Up to 32 transceivers may be connected simultaneously on a
bus, but only one driver should be enabled at any time. It is im-
portant, therefore, that the remaining disabled drivers do not
load the bus. To ensure this, the ADM485 driver features high
output impedance when disabled and also when powered down.
This minimizes the loading effect when the transceiver is not
being utilized. The 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 which results in a logic
high output state if the inputs are unconnected (floating).
The ADM485 is fabricated on BiCMOS, an advanced mixed
technology process combining low power CMOS with fast
switching bipolar technology. All inputs and outputs contain
protection against ESD; all driver outputs feature high source
and sink current capability. An epitaxial layer is used to guard
against latch-up.
The ADM485 features extremely fast switching speeds. Minimal
driver propagation delays permit transmission at data rates up to
5 Mbits/s while low skew minimizes EMI interference.
The part is fully specified over the commercial and industrial
temperature range and is available in an 8-lead DIL/SOIC package.
ADM485–SPECIFICATIONSPOWER SUPPLY CURRENT
Specifications subject to change without notice.
TIMING SPECIFICATIONSSpecifications subject to change without notice.
(VCC = +5 V � 5%. All specifications TMIN to TMAX unless otherwise noted)
(VCC = +5 V � 5%. All specifications TMIN to TMAX unless otherwise noted.)
ABSOLUTE MAXIMUM RATINGS*(TA = +25°C unless otherwise noted)
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7 V
Inputs
Driver Input (DI) . . . . . . . . . . . . . . . . –0.3 V to VCC + 0.3 V
Control Inputs (DE, RE) . . . . . . . . . . –0.3 V to VCC + 0.3 V
Receiver Inputs (A, B) . . . . . . . . . . . . . . . . . –14 V to +14 V
Outputs
Driver Outputs . . . . . . . . . . . . . . . . . . . . . . . –14 V to +14 V
Receiver Output . . . . . . . . . . . . . . . . . –0.5 V to VCC +0.5 V
Power Dissipation 8-Pin DIP . . . . . . . . . . . . . . . . . . . 500 mW
θJA, Thermal Impedance . . . . . . . . . . . . . . . . . . +130°C/W
Power Dissipation 8-Pin SOIC . . . . . . . . . . . . . . . . . 450 mW
θJA, Thermal Impedance . . . . . . . . . . . . . . . . . . +170°C/W
Power Dissipation 8-Pin Cerdip . . . . . . . . . . . . . . . . 500 mW
θJA, Thermal Impedance . . . . . . . . . . . . . . . . . . +125°C/W
Operating Temperature Range
Commercial (J Version) . . . . . . . . . . . . . . . . . 0°C to +70°C
Industrial (A Version) . . . . . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . +300°C
Vapour Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent 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
sections of this specification is not implied. Exposure to absolute maximum ratings
for extended periods may affect device reliability.
Table I.Transmitting
Table II.Receiving
PIN FUNCTION DESCRIPTION
PIN CONFIGURATION
ORDERING GUIDE
CAUTIONESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the ADM485 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.
ADM485
Test CircuitsFigure 1.Driver Voltage Measurement Test Circuit
Figure 2.Driver Voltage Measurement Test Circuit 2
Figure 3.Driver Propagation Delay Test Circuit
OUTCLCCL0V OR 3V
DE INFigure 4.Driver Enable/Disable Test Circuit
LOUTREFigure 5.Receiver Propagation Delay Test Circuit
OUTCCL
RE INL
+1.5V
–1.5VFigure 6.Receiver Enable/Disable Test Circuit
Figure 9.Receiver Propagation Delay
Switching CharacteristicsFigure 7.Driver Propagation Delay, Rise/Fall Timing
Figure 11.Receiver Output Low
Voltage vs. Output Current
Figure 14.Receiver Output Low
Voltage vs. Temperature
Figure 17.Driver Output Low
Voltage vs. Output Current
Figure 12.Receiver Output High
Voltage vs. Output Current
Figure 15.Driver Differential Out-
put Voltage vs. Output Current
Figure 18.Driver Output High
Voltage vs. Output Current
Figure 13.Receiver Output High
Voltage vs. Temperature
Figure 16.Driver Differential Output
Voltage vs. Temperature, RL = 54 Ω
Figure 19.Supply Current vs.
Temperature
Figure 20.Receiver tPLH–tPHL, vs.
Temperature
Figure 23.Loaded Driver
Differential Outputs
ADM485–Typical Performance CharacteristicsFigure 21.Driver Skew vs.
Temperature
Figure 24.Driver/Receiver Propa-
gation Delays Low to High
Figure 22.Unloaded Driver
Differential Outputs
Figure 25.Driver/Receiver Propaga-
tion Delays High to Low
RTFigure 26. Typical RS-485 Network
