GENERAL DESCRIPTION：

The ADM1485 is a differential line transceiver suitable for highspeed bidirectional data communication on multipoint bus transmission lines. It is designed for balanced data transmission andcomplies with both RS-485 and RS-422 EIA Standards. The partcontains a differential line driver and a differential line receiver.Both the driver and the receiver may be enabled independently.When disabled, the outputs are three-stated.The ADM1485 operates from a single 5 V power supply. Excessivepower dissipation caused by bus contention or by output shortingis prevented by a thermal shutdown circuit. This feature forcesthe driver output into a high impedance state if, during fault conditions, a significant temperature increase is detected in the internaldriver 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 ADM1485 driver features high outputimpedance when disabled and also when powered down.

This minimizes the loading effect when the transceiver is not beingused. The high impedance driver output is maintained over theentire common-mode voltage range from –7 V to +12 V.The receiver contains a fail-safe feature that results in a logichigh output state if the inputs are unconnected (floating).The ADM1485 is fabricated on BiCMOS, an advanced mixedtechnology process combining low power CMOS with fastswitching bipolar technology. All inputs and outputs containprotection against ESD; all driver outputs feature high sourceand sink current capability. An epitaxial layer is used to guardagainst latch-up.The ADM1485 features extremely fast switching speeds. Minimaldriver propagation delays permit transmission at typical data ratesof 30 Mbps while low skew minimizes EMI interference.The part is fully specified over the commercial and industrialtemperature range and is available in PDIP, SOIC, and smallMSOP packages.

FEATURES：

Meets EIA RS-485 Standard

30 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 LTC1485

APPLICATIONS：

Low Power RS-485 Systems

DTE-DCE Interface

Packet Switching

Local Area Networks

Data Concentration

Data Multiplexers

Integrated Services Digital Network (ISDN)