ADM485

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5 V, Low Power, 5 Mbps, Half Duplex EIA RS-485 Transceiver

Data Sheet (Rev. F) Product Selection Table
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Overview

  • Meets EIA RS-485 Standard
  • 5 Mbps 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
  • Driver Propagation Delay: 10 ns
  • Receiver Propagation Delay: 15 ns
  • High Z Outputs with Power Off
  • Superior Upgrade for LTC485

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.
ADM485
5 V, Low Power, 5 Mbps, Half Duplex EIA RS-485 Transceiver
ADM485 Functional Block Diagram
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Documentation

Data Sheet 1

Application Note 2

Informational 1

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Tools & Simulations

ADM485 IBIS Model 1

Evaluation Kits

eval board
schematic 1
EVAL-RS485HDEBZ

Standard RS-485 Half-Duplex Evaluation Board, EVAL-RS485HDEBZ

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Product Details

The EVAL-RS485HDEBZ allows quick and easy evaluation of half-duplex RS-485 transceivers with standard 8-lead SOIC footprints. The evaluation board allows interfacing via screw terminal block to digital I/O for driver input (DI), receiver output (RO), driver enable (DE) and receiver output (RO). Bus signals A and B (half-duplex bus) can be connected to a bus screw terminal block. One or two termination resistors can be connected to A and B via jumper settings, in order to evaluation the half-duplex RS-485 driver and receiver. Footprints are provided for pull-up and pull-down (biasing resistors) on the bus.

Devices for evaluation on the board must be ordered separately.
EVAL-RS485HDEBZ
Standard RS-485 Half-Duplex Evaluation Board, EVAL-RS485HDEBZ
EVAL-RS485HDEBZ Image

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