Abstract: Overvoltage protection circuits include a combination of an overvoltage detection circuit and a voltage clamping circuit that inhibits sustained overvoltage conditions. An overvoltage detection circuit can include first and second terminals electrically coupled to first and second power supply signal lines, respectively. This overvoltage detection circuit may be configured to generate a clamp activation signal (CAS) in response to detecting an excessive overvoltage between the first and second power supply signal lines. This CAS is provided to an input of the voltage clamping circuit, which is electrically coupled to the first power supply signal line and configured to sink current from the first power supply signal line in response to the CAS. The voltage clamping circuit may be configured to turn on and sink current from the first power supply signal line in-sync with a transition of the CAS from a first logic state to a second logic state.

Abstract: Within a dual gate oxide process, gate oxide is formed within regions on a substrate. Gate material, such as polysilicon, is placed over a first region. The gate material extends over field oxide surrounding the first region. Gate oxide within a second region is stripped. The gate material over the first region prevents gate oxide within the first region from being stripped. A new layer of gate oxide is formed within the second region. A first transistor gate is formed within the second region. The gate material which is over the first region is etched to form a second transistor gate.