To be compliant with electromagnetic compatibility standards, integrated circuits such as microcontrollers have to be robust to fast transient burst tests. The supply pins, their numbers and their respective positions, can have an influence on the robustness of circuits on ESD (ElectroStatic Discharges) and FTB (Fast Transient burst) tests. For cost reasons, this number of supply pins tends to be reduced for the benefit of I/O in order to increase the functionalities of the microcontrollers. The objective of this work is to study the impact of the number and the placement of these supply pins on the FTB tests. A quick explanation of the different results is also proposed to conclude this study.