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ESD protection of LED to IC lines

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jelydonut

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I have recently discovered that a 4kV ESD event was causing my board to fail due to a discharge on the RJ45 shield, which then traveled to the LED and into the IC causing it to fail.

What is a good way to protect that IC for FCC cert, and is there a good doc/example out there? I did put protection on the datalines, but didn't think of the LED lines.

Thanks!!

jelydonut
 

SunnySkyguy

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All ancient keyboards with LEDs failed the same way with a 5mm LED exposed and 1kV/mm in air possible BDV (arc) depending on humidity.

... if caused by ground shift , a + pulse if it creates more than -10v into rail protection diodes if exist will fry LED rated for only -5V.. Adding reverse protection diode will help.

CM choke also raised impedance to current peak.

Insulating the shield if possible and connecting drain wire to frame and not PCB may help with CM choke.
 

marce

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Are we talking about an 8P modular connector used for Ethernet, or some other interface...
If Ethernet the internals should be laid out with caps and magnetics to avoid this happening... to a greater extent. The shield should be isolated from the rest of the designs ground by caps as per the numerous layout notes as well as an ESD device (and array od diodes) to combat this problem.
If it is being used for another type of interface then what are its specs....
RJ stands for Registered Jacks a telecom standard for the various forms and uses of Modular connectors.
 

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