Altera Device-Specific Power Delivery Network Bedienungsanleitung PDF herunterladen (Seite 7)

Chapter 1: User Guide for the Device-Specific Power Delivery Network (PDN) Tool 1–3

PDN Decoupling Methodology Review

September 2012 Altera Corporation Device-Specific Power Delivery Network (PDN) Tool User Guide

target

is defined using the maximum allowable voltage ripple and transient current

and is calculated as follows:

For example, to reliably decouple a 3.3-volt power rail that allows 5% of AC ripple

and a maximum 2 A current draw, 50% of which is transient current, the desired

target impedance is:

To accurately calculate the Z

target

for any power rail, the following information must

be known:

■ The maximum transient current requirements for all devices in the system that are

from manufacturers of the respective devices. You can calculate the maximum

transient current of a device using the maximum total current and the transient

current percentage.

1 The percentage of transient current is signal-pattern dependent. It changes

as the output signal pattern varies for drivers using the power rail. You

need to choose the value that represents the worst-case scenario of the

power rail. For information about recommended settings, refer to the table

in the Introduction tab of the PDN tool. Table 1–1 on page 1–4 is from the

PDN tool for a Stratix IV GX device. It lists the Stratix IV GX default power

supply voltage, the recommended settings of the transient current

percentage, and the allowable voltage ripple for power rails.

1 You can obtain accurate estimations on the maximum total current for

Altera devices using the Altera PowerPlay Early Power Estimator (EPE)

tool or the Quartus II PowerPlay Power Analyzer tools. You can download

the EPE tool for your target Altera device from the PowerPlay Early Power

Estimator (EPE) and Power Analyzer.

Equation 1–1.

Equation 1–2.

TARGET

VoltageRail

%Ripple

100

------------------- -







MaxTransientCurrent

----------------------------------------------------------

TARGET

3.30.05

2 x 0.5

--------------------------- -

0.165==

1 2 3 4 5 6 7 8 9 10 11 12 ... 31 32

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