This paper presents an investigation of aging-aware safe operating regions for dc-dc CMOS switching converter output stage pass transistors considering. As a result of increased reliability problems in sub-micron CMOS technology, safe operating area (SOA) diagrams have been replaced by plots that also consider aging-induced performance degradation. Therefore, breakdown and aging mechanisms are thoroughly investigated pertaining specifically to switching converter operation. In this study, transient simulation results are re-evaluated and a novel format is proposed with an insight on pass transistor safe operating region, which enables determining operation regions of pass transistor regarding the breakdown and aging effects. The evaluation of results with the proposed format also help on deciding the amount of supply trace inductances and the strength of the pre-driver to ensure safe operation of pass transistors.