Development of a Low EMI Micro-controller Package for Automobile Applications

For ECUs the common-mode current is the main cause of EMI problems. In this paper, the mechanism of common-mode current generation and an effective way to reduce it is considered theoretically. From the consideration it is obtained that the common-mode current caused by the differential-mode current can be suppressed by means of adjusting the impedance of a PCB to be balancing adequately. And a package in which the impedance adjusting circuit and oscillator circuit is implement is developed for a micro-controller. The measurement shows that the developed package can reduce the common-mode current generation compared to the conventional QFP package. And the developed package can minimize the value of the common-mode current by means of adjusting the inductance of the power bus line in the package.