ESD Current path flow on this Diagram

Question

I was reading about ESD diode arrays and protection devices and saw this question over here.

My question is:

In this diagram below, can someone help me to draw/identify the path of current flow through the ESD diode (RClamp part) when an ESD strike occurs?

Also, I saw the datasheet of the Rclamp part over here.

I think that the arrangement of the diodes of the Rclamp part is different from the one in the question and the one in the datasheet. Can someone clarify which one is better?

Also, I would be grateful if the current path for the datasheet part is also helped with. Thank you.

Answer 1

As per your example of what happens if ESD strikes on pin 1 of RJ45 connector.

As Ethernet is a transformer coupled interface, it would mean that ESD current going into pin 1 would have to come out from pin 2, so it just applies a pulse on the transformer coil. It would generally not jump over through the transformer directly.

The pulse would couple from transformer primary to secondary, and would try to apply differential voltage of the data pair, pushing one wire high above supply voltage and the other wire low below ground voltage.

The ESD protection device would then clamp the voltage that tries to go below GND to GND by conducting current, and also clamp the voltage that tries to rise above the TVS voltage to ground by conducting current.

Answer 2

In the long tradition of crudely drawn lines -- just follow the diodes. The tilted lines on the zener (huh, kinda like a 'Z', innit?) means current flows through it given enough voltage (which is given here).

Take your pick of which line(s) to apply to. In this case, either pin 1 went positive, and/or pin 10 went negative. Current may flow between pairs, or from one or both lines to/from ground, depending on intensity and bias voltage.

Answer 3

The diode arrangements are exactly the same.

The first diagram does not show the important components, i.e., the ground connection and the power supply's decoupling capacitors. But that is where the current flows.

Once the current spike is on the ground line, the decoupling capacitors eat the charge. (ESD strikes do not have much energy, so the capacitors' voltage does not change much.) If you have a multilayer board, the power/ground planes can act as a capacitor.

In theory, you could put a capacitor directly on the signal line, but this would filter out high-frequency signals.