Using the MAX3157 High-CMR RS-485 Transceivers

Abstract: This application note describes functional operation of MAX3157 RS-485 transceiver with ±50V isolation and internal power transfer across the isolation barrier. Common-mode signals are described, and the origin of CMR voltages in a balanced wired communication circuit is described.Cable grounding conventions are suggested, and limits of ground-potential difference vs. frequency are graphed.