ADM1486

The ADM1486 is a differential line transceiver suitable for high speed bidirectional data communication on multipoint bus transmission lines. It is designed for
balanced data transmission, complies with EIA Standards RS-485 and RS-422 and is recommended for PROFIBUS applications. The part contains a differential line driver and a differential line receiver. Both the driver and the receiver may be enabled independently. When disabled or with power off, the driver outputs are tristated.

The ADM1486 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 50 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 ADM1486 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 ADM1486 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 ADM1486 features extremely fast switching speeds. Minimal driver propagation delays permit transmission at data rates up to 50 Mbits/s while low skew minimizes EMI interference.