Altera Stratix IV GX Manual page 7

Chapter 1: Power Delivery Network (PDN) Tool User Guide for Stratix IV Devices
PDN Decoupling Methodology Review
Z
target
and is calculated as follows:
Equation 1–1.
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:
Equation 1–2.
To accurately calculate the Z
known:
■ The maximum transient current requirements for all devices in the system that are
powered by the power rail under consideration. You can obtain this information
from manufacturers of the respective devices.
1
1
■ The maximum allowable AC ripple on the power rail as a percentage of the supply
voltage. You can obtain this information from the power supply tolerance
specifications of the devices being supplied by the power rail under consideration.
Table 1–1
transient current percentage, and the allowable voltage ripple for power rails of
Stratix IV GX devices.
Table 1–1. Settings for Some Stratix IV GX Device Power Rails (Sheet 1 of 2)
Rail Name
VCC
VCCIO
© March 2009 Altera Corporation
is defined using the maximum allowable voltage ripple and transient current
Z
TARGET
Z
target
The content of transient current is signal-pattern dependent. It changes
from rail to rail 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 the recommended settings for different
power rails, refer to
You can obtain more accurate estimations on maximum transient current
for Altera devices using the Altera PowerPlay Early Power Estimator
®
(EPE) tool, a program to estimate power consumption for all its FPGA and
CPLD devices. You can download the EPE tool for your target Altera device
from the PowerPlay Early Power Estimator (EPE) and Power
lists the default power supply voltage, the recommended settings of the
Allowable Ripple
Voltage (V) Percentage (±)
0.9 V 5%
1.2 V - 3.0 V 5%
%Ripple
⎛
•
VoltageRail ------------------- -
⎝
=
--------------------------------------------------------- -
MaxTransientCurrent
( ) 0.05 ( )
3.3
--------------------------- - 0.165Ω
= =
TARGET
2 x 0.5
for any power rail, the following information must be
Table 1–1.
(Note 1)
Transient Current
Percentage (%)
50%
50%
Power Delivery Network (PDN) Tool for Stratix IV Devices User Guide
⎞
⎠
100
Analyzer.
Notes
Core
I/O Bank
1–3