high - side physical interface driver circuit , for use in a variety of data transmission applications , includes an external connection for connecting and providing drive current to an external physical interface . output transistor for channeling high - side drive current to external connection . output transistor includes base , collector , and emitter . control transistor controls the on state of output transistor to supply high - side drive current to external connection . at least one shorting transistor shorts base of output transistor to emitter , when high - side voltage reaches a predetermined minimum voltage level . the breakdown prevention circuitry , including transistors , , , as well as associated circuitry , couples with control transistor for preventing control transistor from shorting due to breakdown of parasitic diodes when the high - side physical interface driver circuit reaches a predetermined maximum value .