Electrical approach to acoustic noise for MLCCs of power delivery network in mobile system

In this paper, the authors propose an effective methodology to detect capacitors generating audible acoustic noise in power delivery network of mobile system. Most of capacitors are exposed to coupling noises; TDMA (Time Division Multiple Access) in GSM (Global System for Mobile communication) operates in every 217Hz. The dielectric material and electrolyte of MLCCs (Multilayer Ceramic Capacitors) have stressed due to AC voltage droop synchronous to TDMA operation. Hence, the voltage droop on MLCCs can be used as an electrical key element to figure out how much MLCCs are vibrating among hundreds of capacitors in mobile system. AC voltage droop on MLCCs is examined by measurement and simulation as well as are well correlated. In addition to, an amplitude of each MLCC is measured in its TDMA harmonics and the most vibrated MLCC is consistent with the MLCC which is the most dropped in every 217Hz.