Tool/software:
Hi Team,
As I know, most of ESD are bidirectional structure. It can both positive and negative ESD strikes. And I am weird whether there is a scenario that only needs to be protected against only positive ESD strikes.
It looks like bi-directional is better than uni-directional. Why we develop the uni-directional ESD?
Regards,
Roy
Hi Roy,
Unidirectional devices can still clamp negative ESD strikes,in fact they have a lower breakdown voltage in the negative polarity so they will have a lower clampng voltage for negative ESD strikes. These are preferred for interfaces such as USB that only swing in the positive range, as the controller IC's are typically very sensitive to negative voltages.
Here are snippets the positive and negative TLP curves. If you compare the clamping voltage at different TLP currents you'll notice the negative strike (GND to IO) has lower clamping voltage for the same TLP current.
Our ESD Fundamentals Training goes into further detail on these topics.
Regards,
Sebastian
