AN2586 Freescale Semiconductor / Motorola, AN2586 Datasheet - Page 16

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

Previous Work Study
Previous Work Study
3.4 What can be done with the PDN model?
When a circuit model is extracted from the layout, the design engineer can do the circuit analysis needed to
proof that the layout comply with constraints. For example, the model of the board can generate a system
equation like the following:
Where V is the node voltages across the mesh thus from the circuit designer’s point of view, the power
distribution system resembles Figure 13:
Layout and circuit designers are interested in the overall circuit behavior, including the supply, DC/DC
converter for instance, model, and bypass capacitors network that are close to the chip and the supply and
in the PSD network.
The circuit engineer might be interested in achieving the following constraint, for example, where Vi is any
voltage node in the PDS for all times:
. The design challenge is how to achieve this goal using the following:
3.5 Where to place the decoupling capacitor?
The issue of placing the decoupling cap involves the following:
16
•
•
•
•
•
•
Bypass capacitors network
Selection of optimum number of bypass capacitors
Selection of optimum location of the bypass capacitors
Modification of layout geometry
Capacitor model
Decoupling route model
Via model
MPC8260 PowerQUICC II Family Power Distribution Trends: A Survey
DC/DC
convert
output
model
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
Vi t ( )
Figure 13.
Z
V
≤
=
cons
ZI
tan
t
Bypass capacitors network
Chip die
and package
MOTOROLA