SIGNAL CHAIN BASICS #67: How to design a two-to-four wire converter for RS-485

Multipoint data communication networks such as Profibus, Modbus, and BACnet often require interoperability of RS-485 two-wire, half-duplex and four-wire, full-duplex bus systems.

These systems can extend to several hundreds of meters and are subject to large ground potential differences (GPD). These potential differences can exceed the common-mode voltage range of a transceiver and damage the device.

To eliminate GPDs, galvanic isolated transceivers are used to separate a bus node’s control electronics from the actual transceiver stage connected to the bus.