The impact of capacitors selection and placement to the ESL and ESR

Abstract

High frequency capacitors are used in the power delivery network for decoupling solution. From the impedance in frequency domain, those capacitors which are located near the load current provides the high frequency decoupling solution rather than the capacitors further away. Therefore, embedded package capacitors are desired due to its high frequency decoupling effect. However, in high frequency region, inductance of the capacitors (ESL) is sensitive and can introduce high resonant in the power delivery network. The resonance causes large spike or droop if the resonate frequency is hit. In order to reduce the ESL, the placement of capacitors is important to create smaller loop inductance. The paper discusses the methodology used to model the actual capacitor placement using electrical parameters. A study on the two terminal capacitor for various package designs is done to investigate the impact of different geometry. The paper also discusses the impact of series resistance to the power delivery resonance and how it can be optimized in the capacitor placement.