Altera Device-Specific Power Delivery Network - Manual (Page 5)

September 2012 Altera Corporation Device-Specific Power Delivery Network (PDN) Tool User Guide
1. User Guide for the Device-Specific
Power Delivery Network (PDN) Tool
This user guide provides a brief overview of the various tabs in the device-specific
PDN tool. You can quickly and accurately design a robust power delivery network by
calculating an optimum number of capacitors that meet the target impedance
requirements for a given power supply.
Overview
PCB designers must estimate the number, value, and type of decoupling capacitors
needed to develop an efficient PCB decoupling strategy during the early design
phase, without going through extensive pre-layout simulations. Altera’s Power
Delivery Network (PDN) tool provides these critical pieces of information.
Because all device-specific PDN tools have a similar user interface, this document
serves as the user guide to all Altera
® device-specific PDN tools. The device family
being supported by the tool is shown on the top-right corner of the major tabs of the
tool.
f
For more information about Altera’s general purpose PDN tool with no device
support, refer to the
Power Delivery Network (PDN) Tool User Guide .
The PDN tool is a Microsoft Excel-based spreadsheet tool used to calculate an
impedance profile based on user inputs. For a given power supply, the spreadsheet
requires only basic design information, such as the board stackup, transient current
information, and ripple specifications to calculate the impedance profile and the
optimum number of capacitors to meet the desired impedance target (Z
TARGET
). The
tool also provides device- and power rail-specific PCB decoupling cut-off frequency
(F
EFFECTIVE
). The results obtained through the spreadsheet tool are intended only as a
preliminary estimate and not as a specification. For an accurate impedance profile,
Altera recommends a post-layout simulation approach using any of the available
EDA tools, such as Sigrity PowerSI, Ansoft SIWave, Cadence Allegro PCB PI, etc.
Application of the Tool
The purpose of the PDN tool is to help the design of a robust power delivery network
for the device in the targeted device family by determining an optimum number, type,
and value of decoupling capacitors needed for selected device/power rail to meet the
desired Z
TARGET
up to F
EFFECTIVE
. This spreadsheet tool is useful for exploring the
various what-if scenarios during the early design phase, without extensive and time
consuming pre-layout analysis.
PDN Decoupling Methodology Review
This section describes general PCB decoupling methodology and explains in detail
the two parameters (Z
TARGET
and F
EFFECTIVE
) provided by the PDN tool for guiding
PCB decoupling design.