Effects of On-Chip Decoupling Capacitor on Switching Noise and Radiated Emission

Simultaneous switching noise and electromagnetic radiation in electronic systems are becoming serious problems with the increase in operating speed of digital circuits. Recently, it was recognized that LSI chips are primary sources of electromagnetic radiation. This paper presents experimental results using two types of test chips, one with and one without an on-chip decoupling capacitor. The effects of the on-chip decoupling capacitor on radiated emission and simultaneous switching noise were characterized by activating I/O circuits or core logic circuits. More than 5 dB of electromagnetic radiation were reduced with the implementation of the on-chip decoupling capacitor for core logic operation.