A weakly driven output driver circuit can be susceptible to pulsed radiated and conducted electromagnetic interference (EMI) noise sources. Transients from EMI sources can cause the output driver to change state, resulting in false output pulses or no output at all. This issue can be exacerbated if the driver is connected to a load circuit via a long conductor. The long conductor can act as an antenna that couples the EMI into the circuit to cause transient errors.
Various techniques can be used to reduce a circuit's susceptibility to electromagnetic interference. These techniques include improving shielding of the circuit or cable, addition of ferrite beads, filtering, modification of ground and power plane routing, etc. However, these techniques can be expensive or impractical in certain circuits. If, for example, the driver circuit is part of a remote sensor, it may be difficult to modify ground and power routing, or cost prohibitive to add shielding or ferrite beads.
In certain instances, overstress current (e.g. current caused by an overstress condition such as EMI or electrostatic discharge (ESD)) flowing through an integrated circuit may result in the injection of minority carriers into the circuit's substrate. If the minority carriers are electrons in a p-doped substrate, the electrons may remain in the substrate without recombination for relatively long period of time and diffuse considerable distances through the substrate to reach other sections of the circuit, where they may be collected by a positively biased n-tubs. The currents associated with the collection of electrons by other n-tubs can cause malfunction in other circuits.
USPTO Backgrounds
USPTO Backgrounds