Circuit Protection of Serial Port
The signals used in an RS-232 port can vary between -12V to +12V, with a maximum data rate of 256kbps. Since this is a low-speed system, the capacitance of the suppress is not a concern. The signal lines to be protected from ESD include RD, TD, RTS, CTS, DSR and DTR.
As shown at the left, discrete multilayer varistors can be used for board layout flexibility, or to reduce part count, a single rail clamp device can be used.
Other solutions within the Ruilon portfolio exist in addition to these recommendations. For example, if the signal voltages will be limited in the range from -5V to +5V, then an MLV with a lower operating voltage can be chosen.
The IEC 61000-4-2 will be the most appropriate standard that applies for this port. It supplies a test method for verifying that the end product is not susceptible to ESD events.
Unique Features:Does not apply.
Application Warnings:Does not apply.