Internal chip ESD phenomena beyond the protection circuit

Input/output electrostatic discharge (ESD) circuit requirements call for good protection of the pin with respect to both the ground and the power bus pins. Although effective protection can be designed at the pin many cases of damage phenomena are known to occur internal to the chip beyond the protection circuit. Here, the issues of protection between V_DD and V_SS are discussed first. This is followed by examples of how protection circuit performance can be sensitive to internal chip layout, independent of its effective design. Several illustrative actual case studies are reported to emphasize the internal chip ESD phenomena and their adverse effects