Research On Modeling And Decoupling Design Of Distributed Power Distribution Network

Power integrity has become one of the main problems in high-speed circuit design.With the development of electronic system to higher frequency,higher speed,and higher density,the design of power integrity in the next ten years will face more severe challenges.Power distribution network is the most complex interconnection structure in high-speed digital systems.With the increase of clock frequency,the power distribution network gradually shows the distribution characteristics.Decoupling capacitors gradually exhibit local effects.The focus of decoupling design is gradually shifted to the placement of decoupling capacitor on the power distribution network.And the basic algorithm of decoupling design of the distributed power distribution network is still to be improved.This paper focuses on modeling and decoupling design of power distribution network in highspeed circuit system.The efficiency and accuracy of the presented methods are analyzed and verified in detail.The main contributions of this dissertation are as follows:1)Since the resonant cavity algorithm cannot model the power/ground plane pairs with load and that with arbitrary shape,an algorithm was proposed to model the power/ground plane with capacitors,which extends the application of the resonant cavity algorithm.This method can not only deal with the power/ground plane with capacitor,but also can be applied to the power/ground plane with other single port load.The computational efficiency and accuracy of the algorithm depend on the number of resonant modes.The more resonant modes are used,the higher the computational accuracy,but the lower the computational efficiency.By being combined with the inductance approximation method and the Double-Frequency approximation method,the efficiency of the proposed algorithm is improved greatly.The application of the proposed method is extent to the power/ground plane with irregular shape by being combined with the segmentation method and the reverse compensation method.This proposed method can be the basic algorithm for the decoupling design of distributed power distribution network.The correctness of this algorithm is verified by the comparison with the simulated results by HFSS.2)Based on the resonant cavity algorithm,a modeling method for the power/ground with multi-port load is presented to solve the problem that the resonant cavity algorithm cannot be used to computed the impedance of the multi-layered power/ground structure.In the multi-layered power/ground plane structure,planes with the same potential are connected together by vias.When the observation port is on the top plane pair,the remaining plane pairs can be considered as the multi-port load of the first plane pair.This algorithm can effectively calculate the frequency domain characteristics of the multi-layered power/ground plane structure,and extend the application of the resonant cavity algorithm to the multilayered power/ground plane.It provides an algorithm basis for decoupling design of multilayered power distribution network.The correctness of this algorithm is verified by the comparison with the simulated results by HFSS.3)In view of the reflection caused by of the stub of differential via in multi-layered PCB,a high impedance termination method is proposed to improve the signal at the receiving end and to reduce the influence of the via stub.The reflection between differential open via stub and its high-impedance resistive termination is used to improve the DC voltage level.But due to the reflection,there is severe delay in the rising edge of the received signal.Then,the reflection gains between the receiving end and its high inductive termination is used to improve the rising edge of the received signal.4)According to the impedance distribution throughout the whole power/ground plane,the calculation method of the decoupling radius is put forward.In the area characterized by the decoupling radius,the impedance of the power/ground plane is smaller than the target impedance.In other words,the decoupling capacitor can be placed anywhere in the area characterized by the decoupling radius.According to the placement of decoupling capacitors on the power/ground plane,a decoupling method based on the decoupling radius is proposed.By using this method,not only the type and the number of the selected capacitors,but also the locations of the decoupling capacitors can be obtained.5)Based on a signal RL line model of the on-chip power distribution network,the computation method of the decoupling radius of decoupling capacitor is proposed.The charging radius of the decoupling capacitor is constrained by the target noise,and the length of the discharge radius depends on the length of the charge radius and the target noise.The conversion coefficient that converts the radii of a decoupling capacitor in a signal RL line model into the equivalent one in a meshed model is presented as a constant.By comparing the simulated results by HSPICE,the accuracy of the conversion coefficients is verified.The charge and discharge radii of the decoupling capacitor in the single line RL model can also be applicable to a RLC meshed network.The modeling and decoupling method of the power distribution network is studied systematically in this dissertation,and all results are validated by strict simulations.Hence,the results can be directly used in the actual designs.