AN2586 Freescale Semiconductor / Motorola, AN2586 Datasheet - Page 15

• Manufacturer Part Number: AN2586
• Description: MPC8260 PowerQUICC II Family Power Distribution Trends
• Manufacturer: Freescale Semiconductor / Motorola

3.3 How to model the power distribution network?
Designing, modeling and analyzing the power distribution network involves many considerations, such as
the following:
Derive a clear view for these issues and an optimal solution that satisfies all the requirements. When the
layout is done, verify if it is going to achieve all the goals. Modeling can be done in many different methods,
all dependent on the following:
Two main methods can simulate the 3D structures:
Many available commercial tools can do all of these methods.
The main idea is based on Maxwell’s equations that deals with E, D, H, B in real time. Then an attempt is
made to put constraints, boundary values, based on the 3D geometry that the layout engineer provides.
These equations are made discrete in both time and space, with an accuracy level that is consequently lost.
When the tools have the discrete equation that can be represented in a matrix format, the tools attempt to
solve these matrices given an input and a desired output. Many results can be obtained and used to study the
behavior of the design as well as to do the ‘what if’ analysis to optimize the design.
Many methods can simplify the simulation analysis by reducing the amount of computation time. Some of
these techniques are based on the TLM method where the power plan is a mesh of transmission lines. A
SPICE-like simulator solves the system equation accordingly (see Figure 12):
MOTOROLA
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1. How accurate is the model?
2. What is the computing capacity?
3. What kind of results are desired?
1. Full wave analysis, such as the following:
2. Partial element equivalent circuit method, PEEC
How many power planes are needed and why?
What is the stack up arrangement?
What is the DC capacity of my power plan? Can it handle enough current whithout overstressing?
What are my mechanical and physical constraints? Do I have enough estate to deliver generous
currents?
Do I want to take care of EMI issues up front?
What about coupling? What constraints do I have for signal integrities?
— Finite element Method FEM
— Method of Moments MoM
— Finite difference time domain method, FDTD
Each segment of the
mesh is a transmission
line circuit model.
MPC8260 PowerQUICC II Family Power Distribution Trends: A Survey
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
power
output port
Figure 12.
input port
ground
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