Protect RS-485 Transceivers from Electrical Surges—and Maintain Signal Integrity (.PDF Download)

The RS-485 is a popular serial communications standard that’s widely used in industry. It’s flexible, with the ability to achieve high data rates on long bus cables. The standard is relatively easy to implement, too, using available IC transceivers. However, one serious limitation is its vulnerability to electrical surges generated by nearby equipment. This problem has now been solved thanks to integrated protection circuitry, making the RS-485 almost “bulletproof.”

Review of RS-485

RS-485 is a national and international standard of the American National Standards Institute (ANSI) and the Electronics Industry Alliance/Telecommunications Industry Association, and is designated EIA/TIA-485-A. It’s a wired communications differential bus made up of unshielded twisted-pair cable that greatly reduces the noise pickup.