Reverse Engineering PCB Board Protection Circuit

Reverse Engineering PCB Board Protection Circuit

Parasitic inductance in the TVS diode path can cause severe voltage overshoot in the event of an ESD event. so in the process of Reverse Engineering PCB Board Protection Circuit, despite the use of TVS diodes, excessive overshoot voltages may still exceed the damage voltage threshold of the protected IC due to the induced voltage VL = L × di / dt across the inductive load.

The total voltage that the protection circuit is subjected to is the sum of the voltage generated by the TVS diode clamp voltage and the parasitic inductance, VT = VC + VL. An ESD transient induced current peaks in less than 1 ns (according to IEC 61000-4-2), assuming a lead inductance of 20 nH per inch, a line length of one-quarter inch, and an overshoot voltage of 50V /10A pulse. The empirical design rule is to minimize the parasitic inductance effect by designing the shunt path as short as possible just like the Signal Integrity In The High Speed PCB Card Reverse Engineering.

All inductive paths must consider ground loops, the path between the TVS and the protected signal line, and the path from the connector to the TVS device. The protected signal line should be connected directly to the ground plane. If there is no ground plane, the ground loop should be as short as possible when PCB Reverse Engineering Rule. The distance between the ground of the TVS diode and the ground point of the protected circuit should be as short as possible to reduce the parasitic inductance of the ground plane.

Finally, the TVS device should be as close as possible to the connector to reduce transient coupling into nearby lines by Reverse Engineering PCB Card Software. Although there is no direct path to the connector, this secondary radiation effect can also cause malfunctions in other parts of the board.