Frequency Analysis of Decoupling Capacitors for Three Voltage Supplies in SoC

Reduction in power consumption has become a major criterion of design in modern ICs. One such scheme to reduce power consumption by an IC is the use of multiple power supplies for critical and non-critical paths. To maintain the impedance of a power distribution system below a specified level, multiple decoupling capacitors are placed at different levels of power grid hierarchy. This paper describes about three-voltage supply power distribution systems. The noise at one power supply can propagate to the other power supply, causing power and signal integrity problems in the overall system. Effects such as anti-resonance and remedies for these effects are studied. Impedance of the three-voltage supply power distribution system is calculated in terms of RLC-model of decoupling capacitors. Further the obtained impedance depends on the frequency; hence brief frequency analysis of impedance is done.