Electromagnetic interference (EMI) becomes a serious issue inelectronic systems with the increase of the operating speed of digitalcircuits. Electromagnetic radiation occurs from cables, connectors,wiring pattern on PCB, LSI packages, heat sink and so on. They work asunwanted antenna. Shielding or filtering at the board level is notalways efficient way to suppress the radiated emission. Recently, LSIchip itself has been recognized as dominant source of EMI. The switchingcurrent of the digital circuits induces the voltage fluctuations ofpower/ground lines, i.e. switching noise, Furthermore, the spreadout ofswitching current to the entire PCB excites the inherent resonance's ofPCB as an antenna. In this paper, the effects of the separation ofpower/ground lines for the core circuits from that for the I/O circuitsand increased on-chip capacitance in a micro-controller chip wereexamined by using TEM (transverse electromagnetic) cell and a near-fieldprobe system. And the combination of power/ground island in PCB for thecore circuits was examined and analyzed by a simplified SPICEmodel
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