Controlling substrate currents in junction-isolated ICs

Substrate currents can cause a variety of difficulties ranging from improper operation to catastrophic failure. The effects of substrate currents are characterized and techniques are developed for avoiding problems. Method of optimizing layout to control substrate currents and their effects are discussed. It is shown that these currents are strongly influenced by the properties of the die-attach interface. Fault conditions that can generate destructive hole and electron current densities in the substrate are described, and IC clamp diodes, often required to control these fault conditions, are analyzed. An example gives an appreciation of what must be considered in the design of a practical IC along with the results that might be expected