Often in automotive applications, a well optimized board with decoupling capacitors in proximity of the Integrated Circuit is used to improve EMC performances in system level. With increased safety concerns on mechanical vibrations that leads to lost interconnections of components, there is demand to have a complete solution inside the IC. Being the car's electrical supply, the alternator has to pass stringent electromagnetic stresses such as Bulk Current Injection, BCI. In addition, due to the fact that the bare die is directly die attached to the slip ring brush holder, there is little space left for external components. The IC itself has to be designed for high immunity to guarantee parametric performance during electromagnetic interferences. This paper compares BCI performances of two silicon versions. The first being designed for typical EMC voltage injection of 2.5V peak and the second version was designed for high immunity against electromagnetic stress after laboratory measurements.