Pad Interface Circuit Gate Oxide Protection

The patent introduces a virtual floating well as an intermediary structure between the pad interface circuit and the external voltage source. This virtual floating well acts as a mediator that isolates the gate oxide layer from the high external voltage (Ex_VDD = 5V) while still allowing the circuit to interface with external devices. The well potential floats dynamically, preventing direct voltage stress on the gate oxide layer while maintaining interface functionality.

The patent implements a protection mechanism that is activated beforehand when the internal supply voltage VDD is not supplied. The virtual floating well structure is pre-configured to cushion and absorb the impact of external voltage Ex_VDD before it can reach the gate oxide layer. This preemptive protection allows the circuit to operate with reduced power consumption while maintaining extended lifespan by preventing voltage-induced degradation in advance.

The patent applies local quality by creating a specialized virtual floating well structure specifically at the pad interface region where voltage stress occurs. Instead of redesigning the entire circuit, the solution locally modifies the well structure at the critical interface point. This localized approach provides enhanced protection to the gate oxide layer exactly where external voltage Ex_VDD applies stress, while keeping the rest of the circuit structure relatively simple and unchanged.