Coupling Paths & Failure Mechanisms
Bursts couple as common-mode current through capacitance and cables. Trace the path from clamp to victim, and see why the failure is usually upset, not damage.
EFT energy arrives as common-mode current: the capacitive clamp or CDN drives the whole cable bundle against the ground plane, and that current flows into the product, through its ground system, and back out. Along the way, the fast di/dt develops voltages across any inductance — bond wires, ground traces, connector pins — and those voltage steps are what upset logic.
The dominant failure is upset: a reset line glitches, a clock or data line sees a false edge, an ADC reference jumps, or firmware wanders. Because the burst repeats, a single weak node fails over and over. Actual damage is uncommon (energy is low) but can happen at exposed I/O without any protection.
On the bench, reproduce the upset, then instrument the suspected victim (scope on reset/power/key I/O) and watch for the glitch that coincides with the burst. Move the clamp along the cable, or test one port at a time, to find which entry point causes the failure — the same delta discipline used throughout the Pre-Compliance course.