iCoupler isolation in RS-232 applications

The RS-232 bus standard is one of the most popular serial communication bus designs. RS-232 was originally specified by the Electronics Industry Association (EIA) in 1962 to communicate between computing equipment and modems. The RS-232 standard is still widely used as an intersystem serial communication link.

The RS-232 standard is a serial data, point-to-point design, with a signal line dedicated for communication in each direction. These two dedicated unidirectional lines result in full-duplex communication.

Although no maximum cable length is specified, maximum practical cable length is approximately 16m. The RS-232's simplicity and flexibility coupled with its long legacy contribute to its continued popularity for intersystem connections.

Because the RS-232 standard is typically used as an intersystem connection, isolation between the bus and each system connected is critical. Digital isolation provides crucial isolation and protection from overvoltage transients between the RS-232 cable bus and the systems connected to it. Digital isolation also eliminates ground loops on the RS-232 bus. Digitally isolating the RS-232 bus from the systems connected to the bus reduces signal distortion and errors, and provides system and component protection from system and bus voltage and ground mismatches.

The intention of this application note is to give the user a brief overview of the RS-232 bus physical layer, as well as an understanding of why isolation is so important to the system. This application note details how to implement isolation for a RS-232 bus using Analog Devices' iCoupler products.

View the PDF document for more information.