An electrostatic discharge (ESD) event refers to a momentary electrical surge causing a current flow to, from, or within a circuit. The momentary electrical surge often causes an excessive amount of current or voltage, which may cause damage to the circuit. Many electrical circuits and devices are susceptible to damage caused by ESD events. ESD protection circuits are usually implemented in a chip to protect the devices and circuits on the chip from ESD damage. Operations of ESD protection circuits generally include one or a combination of the following mechanisms: dissipating an ESD induced current using a low-impedance discharging path, clamping an ESD induced voltage to a predetermined safe level, and similar mechanisms. In some applications, the low-impedance discharge path for the ESD induced current is activated responsive to an ESD event, but is deactivated (e.g., becomes a high-impedance path) during a normal operation of the to-be protected circuit in the absence of the ESD event.
USPTO Backgrounds
USPTO Backgrounds