Low-speed data port

Circuit Protection of Low Speed I/O



Design Notes:

Protection Application:
The signals used in the low-speed input/output ports 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. As an example, if RS-232 protocol is used, the signal lines to be protected from ESD include RD, TD, RTS, CTS, DSR and DTR.
Solution Description:
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.
Companion Solutions:
Other solutions within the Littelfuse 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.
Regulatory Issues:
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.

Solutions

Solutions