Analysis Of Decoupling Capacitors On CPU/GPU Power Distribution Networks

As electronic system with high-desity IC trends to higher operating speed with required features of lower power consumption, lower voltage but higher current since its super high desity, signal and power integrity becomes a great challenge for high-speed digital system design. The power noise, caused by non-deal power distribution network(PDN), will seriously affect power integrity then system reliability of circuit on silicon, such as CPU, GPU, etc. Introducing and selecting decoupling capacitors at different levels is a main measurement to resolve the power integiry issues, through which PDN properties can be improved and optimized. In the traditional way to design a PDN, selection of coupling capacitor mainly relies on the designer's experience, then it might be tunned and adjusted in location per actual measurements on power noise and signal jitter. Clearly, disadaventage of this method is its long design cycle time, high cost and high potential of design iterrations. Therefose, the shortage becoms a bottomneck in the present competitive electronic industry. On the other hands, simulation based PDN analysis and decoupling capacitance evaluation can provide guidance to design per specification in early stage of the design process and further to track whole design cycle to ensure the quality of design. In this way, one-time success rate of a design can significantly increased that is why the method has become more popular in industry today. This paper is mainly focused on PDN analysis and decoupling capacitor evaluation based on simulation. The impact of output signal from decoupling capacitor is also discussed. The main results of the research are listed below:1) Design the experiment to quantitatively analyze the relationship between (1- value of power supply ripple and output signal tremble.2) Extract the S parameter of power distribution network of a CPU and a GPU separately, perform simulations in frequency domain and time domain accordingly, and examine the optimization result of decoupling capacitor in power distribution network.3) Complete the simulation analysis power distribution network based on Lumped model. Establish a generic model for decoupling capacitor and set up a excel-sheet based tool to deal with the model and quantity selection problem of decoupling capacitor.4) Simulate the power distribution network with field computer and analyze the layout of decoupling capacitor.