High-side physical interface driver circuit (10), for use in a variety of data transmission applications, includes an external connection (18) for connecting and providing drive current to an external physical interface. Output transistor (16) for channeling high-side drive current to external connection (18). Output transistor (16) includes base (18), collector (14), and emitter (24). Control transistor (28) controls the on state of output transistor (16) to supply high-side drive current to external connection (18). At least one shorting transistor (30) shorts base (19) of output transistor (16) to emitter (24), when high-side voltage reaches a predetermined minimum voltage level. The breakdown prevention circuitry, including transistors (50), (52), (102 and 116), as well as associated circuitry, couples with control transistor (30) for preventing control transistor (30) from shorting due to breakdown of parasitic diodes when the high-side physical interface driver circuit reaches a predetermined maximum value.