信号完整性分析课件05PhysicalbasisofResistance.pptVIP

Ch4.The Physical Basis of Resistance Mu-Shui Zhang Sun Yat-Sen Univ. 4.1 Translating Physical Design into Electrical Performance 4.2 The Only Good Approximation for the Resistance of Interconnects 4.3 Bulk Resistivity 4.4 Resistance per Length 4.5 Sheet Resistance 4.6 The Bottom Line Understanding the connection between geometry and electrical properties will give us insight into how signals are affected by the physical design of interconnects and feed our intuition about manipulating signal integrity performance by design. T I P The key to optimizing the physical design of a system for good signal integrity is to be able to accurately predict the electrical performance from the physical design and to efficiently optimize the physical design for a target electrical performance. T I P The design process is a very intuitive process. New ideas come from imagination and creativity. These are fed, not by numerically solving a set of equations but by understanding, at an intuitive level, the meaning of the equations and what they tell us. Modeling is the process of translating the physical design of line widths, lengths, thickness, and material properties, into the electrical view of R, L, and C elements. Figure 4-1 shows this relationship between the physical view and the electrical view for the special case of a generic RLC model. Once we have established the topology of the circuit model for an interconnect, the next step is to extract the parameter values. This is sometimes called parasitic extraction. The task then is to take the geometry and material properties and ask how they translate into the equivalent parameter values of the ideal R, C, L, or T elements. We will use rules of thumb, analytic approximations, and numerical simulation tools to do this. The impedance across the ends of the real copper trace behaves very much like an ideal resistor. It has an impedance that is constant in time and frequency. T I P When we extract the resistance of an interconnect