High/low-side hybrid output transistor with high thermal-SOA

A novel high/low-side hybrid output transistor with high thermal safe operating area (SOA) performance was developed. The output transistor was designed by alternatively arranging high- and low-side transistors to enhance the thermal diffusion from self-heated transistors. A 42% increase in the failure energy of the conventional transistor was obtained at 300-μs short-circuit duration, and a further 10–15% improvement was obtained by introducing a Cu redistribution layer (Cu-RDL) of power metal. A 3D-thermal simulation demonstrated that the peak junction temperature was reduced by around 100°C in the hybrid output transistor during clamp inductive switching. The energy capability of the hybrid output transistor also improved from 18 to 31 mJ in the solenoid driver circuit.