ANSYS PI 介绍

February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
AC 谐振分析 • 当高速IC工作时，会在整 个电源地平面内引入一个噪声，如果 噪声的峰值频点刚好和电源地系统的阻抗谐振频点相同，则噪 声就会被放大 • 系统本身的固有谐振无法被消除，只能避免被激发
February 1, 2012
阻抗曲线
ZTarget
Power _ Supply _ Voltage Allowed _ Ripple
Current
Example:
4A 3.3v VRM 2A
3.3v plane
ZTarget(3.3v)
3.3v 5% 82.5m
Switching Power Supply
Electrolytic Bulk Capacitors
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February 1, 2012
February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
SIwave仿真DC问题
电流分布
电压分布
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DC分析的问题
• 设计趋势
– – – – 电压越来越小 电流越来越大 功率越来越高 平面越来越破碎
• 设计目标
– 如何使接收端的接收电压在可允许的范围之内
– 如何避免电源地平面上存在电流密度过大点导致的热可靠性问题
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2A
Target Impendence is the goal that designer should hit !!!
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February 1, 2012
-20dB/decade
1 nH
ESL
5 nH
C 20 nF
100 nF
ESR
0.16 Ω 0.01 Ω
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February 1, 2012
February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
SSO
• Worst Case PD noise (timing)
V=VCC+DV
DI=DI1+ DI2+ …DIn
Common Power Supply
DI1
H L 1 H L 2
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February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
谐振分析
去耦电容优化
Resonant Mode Analysis
*
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Add C2 56pF
February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
去耦电容优化
resonance
Imped ance
C ES LESR
Capac Induc itive tive
+20dB/decade
(Equivalent Series Resistance)
February 23, 2009 Release 14.0 Inventory #002593
CPS回路电感提取
Package Layout
Vdd Vdd CPM
PCB
Vss
Zin Vss
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ANSYS PI 仿真介绍
14. 0 Release
Chapter 1.1: Introduction 褚正浩
Introduction to ANSYS HFSS
高级应用工程师 Zhenghao.chu@ansys.com
What Is Power Integrity?
• 电源完整性分析的主要目标就是能够给芯片电路提供 干净的电源，消除电源噪声对芯片输出信号的影响。

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February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
DI2
H L n
Din
L
Parasitic Inductance (due to Pins, Bond-wire, etc.)
去耦电容优化
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February 1, 2012
Murata
February 23, 2009 Release 14.0 Inventory #002593
去耦电容优化
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February 1, 2012
Murata
February 23, 2009 Release 14.0 Inventory #002593
0.9304 GHz 0.5115 GHz
Board Center at Voltage peak/dip for these modes!
0.3907GHz 0.46696 GHz
0.78147 GHz
Board Center at Voltage node for these modes!
0.2577 GHz
0.8223 GHz
0.64369 GHz
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0.7674 GHz
0.86118 GHz
February 23, 2009 Release 14.0 Inventory #002593
去耦电容优化

Target Impedance Simulations
Target Impedance Specifications Met !
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典型PDS
• Power Delivery System (PDS)
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February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
去耦电容优化
Resonant Mode Analysis
*
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Add C3
February 1, 2012
2.2nF
February 23, 2009 Release 14.0 Inventory #002593
February 23, 2009 Release 14.0 Inventory #002593
PDS impedance composing
Mag. of Z
Z target
|Z|
f
1KHz
1MHz
100MHz
High Frequency Ceramic Capacitors
GH z
Power/Ground Planes
PI要解决的问题
• DC
– 直流压降过大 – 电流密度过高导致温度过高
• AC
– 阻抗谐振分析
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February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
February 23, 2009 Release 14.0 Inventory #002593
去耦电容优化

Built in Capacitor library Select by Vendor and Part number ESR, ESL included Examine component plot and properties
February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
去耦电容源自文库化
Resonant Mode Analysis
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去耦电容优化
Resonant Mode Analysis
*
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Add C1
February 1, 2012
0.33nF
February 23, 2009 Release 14.0 Inventory #002593
VR
Circuits
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February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
February 1, 2012
February 23, 2009 Release 14.0 Inventory #002593
去耦电容优化设计
• 良好的滤波电路至关重要
V=Z*I
电源回路的阻抗
芯片工作时的变化电流
添加去耦电容可以降低电源回路的 阻抗 • 电容如何选型 • 电容如何摆放
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去耦电容优化
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February 1, 2012
Murata
February 23, 2009 Release 14.0 Inventory #002593