The 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 independently. 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 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.
Up to 32 transceivers may be connected simultaneously on a bus, but only one driver should be enabled at any time. It is important, 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 form -7V 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 EDS; all diver 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-pin DIL/SOIC packages.
|Title||Content Type||File Type|
|ADM485: 5 V Low Power EIA RS-485 Transceiver Data Sheet (Rev F, 04/2008) (pdf, 254 kB)||Data Sheets|
|AN-960: RS-485/RS-422 Circuit Implementation Guide (pdf, 245 kB)||Application Notes|
Solving Isolation Challenges in Industrial Automation
This webcast will discuss the role isolation plays in providing protection and reducing the system bit-error-rate, using the specific design challenges of an RS-485 network. Topics to be covered in this presentation will include: Why and when one should isolate, Types of isolation and their advantages, Design Considerations for an RS-485 node (and how this translates to design considerations for signal isolation) as well as many other topics.
EMC, CE Mark, IEC801... What's it all about?
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Evaluation board for evaluating the RS485
The ezLINX™ iCoupler® Isolated Interface Development Environment provides developers with a cost-effective, plug and play method for evaluation eight physical layer, digitally-isolated communication standards.
Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.
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