October 2007

Rev 2

1/15

AN1690

Application note

Fail-safe biasing for ST485EB

Introduction

ST485EB is an RS-485 based interface designed for multipoint differential transmission on a

single twisted pair cable. It allows half duplex bi-directional transmission, long cable lengths

and high data rates.

Typical applications include LANs, industrial (PLC devices), automotive and computer

interfaces.

System evolution in the data communication field has lead to the development of faster

devices with lower data bit error rates. The ST485EB meets all these requirements. Figure 1

shows a typical multipoint bus configuration.

Figure 1.

Typical RS-485 line

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