Investigation on the Behavior of Stacked Devices Within Output Drivers Under ESD Conditions

This work investigates the robustness of a stacked or cascoded driver under electrostatic discharge (ESD) events. Using output driver circuits in an actual I/O system with predrivers and rail-based power clamps, the impacts of all possible predriver connections and stacked-driver sizing are examined with the very fast transmission line pulse. It is verified that, when the input of the predriver connected to the top MOSFET is grounded, the failure current (IT2) is improved by ~ 110%, compared to the worst case where both predriver inputs are tied to VDD. Also, a simple trigger circuit which guarantees the electrical connection for better ESD immunity is proposed.