Electromagnetic radiation and simultaneous switching noise in a CMOS device packaging

Electromagnetic interference (EMI) becomes a serious issue in electronic systems with the increase of the operating speed of digital circuits. Electromagnetic radiation occurs from cables, connectors, wiring pattern on PCB, LSI packages, heat sink and so on. They work as unwanted antenna. Shielding or filtering at the board level is not always efficient way to suppress the radiated emission. Recently, LSI chip itself has been recognized as dominant source of EMI. The switching current of the digital circuits induces the voltage fluctuations of power/ground lines, i.e. switching noise, Furthermore, the spreadout of switching current to the entire PCB excites the inherent resonance´s of PCB as an antenna. In this paper, the effects of the separation of power/ground lines for the core circuits from that for the I/O circuits and increased on-chip capacitance in a micro-controller chip were examined by using TEM (transverse electromagnetic) cell and a near-field probe system. And the combination of power/ground island in PCB for the core circuits was examined and analyzed by a simplified SPICE model