Designing and Modeling for Power Integrity / Swaminathan M.; Chung D.; Grivet-Talocia S.; Bharath K.; Laddha V.; Xie J.Abstract-After providing an overview of the state-of-the-art in power distribution design and modeling, this paper focuses on return path discontinuities (RPDs) for I/O signaling. After briefly describing their importance in the context of simultaneous switching noise, a specific case of RPD based on via discontinuities is discussed in detail in the context of both the frequency-and timedomain waveforms using a test vehicle. The modeling of RPD in practical packages and printed circuit boards is addressed along with substrate coupling due to nonideal reference planes. Finally, a high-impedance power distribution scheme for I/O signaling is presented that can potentially solve a number of RPD-related problems, followed by future challenges.Index Terms-Macro-modeling, passivity, power distribution, power integrity, return path discontinuity, signal integrity.
Multilayered packages and boards, such as high performance server boards, contain thousands of signal lines, which have to be routed on and through several layers with power/ground planes in between. There can be noise coupling not only in the transversal direction through the power/ground planes in such a structure, but also vertically from one plane pair to another through the apertures and via holes. In addition, the continuous increase in power demand along with reduced Vdd values results in significant current requirement for the future chips. Hence, the parasitic effects of the power distribution system become increasingly more critical regarding the signal integrity and electromagnetic interference properties of cost-effective high-performance designs. We present a multilayer finite-difference method (M-FDM), which is capable of characterizing such noise coupling mechanisms. This method allows to consider realistic structures, which would be prohibitive to simulate using fullwave simulators.
Full-wave EM simulations are computationally expensive given the complexity of packaging structures in modern mixed signal systems. Fast methods such as the transmission matrix method are inaccurate as they do not model discontinuities such as metal edges and gaps. In this paper, simple models for the edge effect and gap coupling are developed for the finite difference frequency domain method. Results are presented comparing the accuracy of the proposed method with full-wave simulations and measurements.
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