Effect of Packages on Electromagnetic Noise Emission from Digital IC.

概要

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Comparison is made on electromagnetic emission from digital integrated circuits in different packages. The same 74HC series CMOS logic busbuffers (74 HC245) in DIP, SOP and a bare chip with gold-wire bonding were mounted on a 4-layered printed circuit board (PCB) . Radiated noise was measured with a small loop antenna at a distance of 20 mm from the surface of the PCB. Noise is radiated from each loop, called a 'bypass loop', which consists of pins of each package and a bypass capacitor placed beside it. The measured spectra were compared with theoretical results calculated from switching current obtained by the analog simulator SPICE. As a result, strength of the emission is proportional to the cross-sectional area of a bypass loop. A smaller package gives less noise emission: SOP gives noise-11dB less than DIP for 20-pin packages.
社団法人エレクトロニクス実装学会の論文