Sigrity SPEED2000 Power Ground Noise Simulation模式如何进行电源地噪声分析操作指导-SODIMM
Sigrity Speed2000是时域仿真分析工具,Power Ground Noise Simulation模式可以观测器件的时域电压波形和观测电源地空间电压分布,
以下图为例进行分析
用Speed2000这个工具打开文件
2D视图
3D view
这是一个SODIMM的PCB文件,本例中仿真TOP层4个DRAM的噪声对于电源地的影响,同时观测在噪声激励下,4个DRAM电压时域波形
具体操作如下
- 切换到模式Power Ground Noise Simulation模式,点击Mode,Base Mode,Power Ground Noise Simulation
- 点击check stackup,确认层叠参数无误后,点击ok
- 点击Prepare Power Ground Nets,选择Setup P/Gnets
- 弹出如下界面P/G nets Classification Wizard界面
- 勾选参与仿真的器件,J1,U0-U7
- 点击下一页
- 软件自动识别出了电源和地网络,点击下一页
- 点击完成
- 自动切换到Net Manager界面
- 鼠标右击Enable All nets使能所有网络
- 结果如下
- 点击Assign Capacitor Modes,定义电容模型
- 自动弹出Assign model Manager 界面,定义电容模型,由于本例中电容都使用理想电容,所以直接点击x关闭该界面
- 软件自动切换到Component Manager界面
- 点击C1,点击edit
- 可以看到C1的参数,是一个100nf的电容模型,如需更改,在Definition中修改参数,本例不做修改
- 点击右下角的ok关闭页面
- 同样的,查看其它电容类型的模型,所有连接到VDD这个电源的网络电容都要被使能,使能的component前面有绿色的勾
- 点击Add Excitation,设计激励源
- 仍然自动切换到Component Manager界面
- 本例中需要将U0-U3这4个DRM设置为激励源
由于只需要将DRAM的电源设置为激励源,但是DRAM目前连接了许多非电源网络,设置激励源比较麻烦,所以需要单独创建4个只含有电源和地pin的component代替DRAM,较为简便
设置方法如下
- 回到Net Manager界面,Disable All nets,将所有网络关闭
- 然后仅使能VDD和GND网络
- 回到Layer Selection界面,只打开top层,右下角点击Component图标
- Layout界面如下,所有component都显示出来了
- 点击菜单栏上的Turn off All选项
- 点击Select pins和select图标
- 鼠标左键框选component U0
- 回到Component Manager界面,点击New
- 弹出New界面,点击New Component By Selected Nodes-Net Based,基于网络生成component,代表所有相同的网络都定义连接到同一个ckt node上,方便定义激励参数,本例选择Net Based
生成的新的component如下
如果选择的是pin base
生成的component如下
- 点击新生成的component,点击后面的E,修改component名字
- 修改名字为IN0
- 选中IN0,点击edit,定义器件参数
- 定义激励源参数为分段线性电流源波形
Definition:
I_0 1 2 pwl(0 0 1n 0 1.1n 100m 1.9n 100m 2n 0 3n 0 3.1n 100m 3.9n 100m 4n 0 5n 0 5.1n 100m 5.9n 100m 6n 0 7n 0 7.1n 100m 7.9n 100m 8n 0)
- 然后点击ok
- 弹出SPEED GENERATOR界面,点击确定
- IN0这个component就被使能了
- 同样的操作将剩余的U1,U2,U3生成IN1-IN3,且赋予相同的参数
- 回到workflow界面,点击Setup VRAM&Decaps,设置VRAM和电容参数
- 仍然是Component manager界面,点击Vsource,选中它,右击点击edit
弹出Edit Model界面
由于本例中Vsource已经定义好了只接电源和地的模型,所以不用额外再定义一次,否则类似IN0-IN3一样操作定义一个新的VRAM模型
- 在definition中输入参数如下,设置为直流1.5v的电源75pin接电源,71pin接地
Vin 75 71 1.5
由于仅仅是定义一个VRAM,所以只接一个电源和一个地pin即可
- 然后点击ok
- Vsource的模型就被使能好了
- 点击Specify Sim Time&Options,设置仿真时间
- 设置仿真时长,本例中设置为10ns,时长必须保证波形能够稳定下来,至少为3个波形周期
Timesetp是默认填充的=time/ time step
勾选以下选项,将这些影响都纳入仿真分析
Enabel plane skin effect 使能平面间趋肤效应
Enable transmission line metal loss 使能传输线的导体损耗
Enable dielectric loss and dispersion 使能介质损耗
Enable initial DC analysis 使能初始直流分析
- 点击ok
- 点击Specify Observation(Voltage),定义电压观测点
- 弹出Component Voltage view界面
- 选中IN0,设置IN0的电压观测点
- 鼠标左击VDD,鼠标右击GND
- 点击Add,添加观测点
- IN0的电压观测点就被设置好了
- 同样地给剩下的IN1-IN3和Vsource定义好电压观测点,如下,然后点击ok
注意:vsource的+和-要选择definition中连接的那两个pin,75和71
- 如果需要观测电流观测点击Specify observation(current)进行设置,本例中不观测,跳过即可
- 回到Net Manager界面,右击选择Enable All Nets,将所有网络使能
- 回到workflow界面,点击Auto Mesh Setup
- 弹出Mesh界面,自动网格设置
点击Auotomatically Generate Mesh,进行自动网格设置
- 自动设置好的界面如下,然后点击ok关闭页面
- 点击Error Check and Warning,进行错误和警告的检查
- 下方output界面如下,没有error,如果存在error需要找到位置修复错误
- 点击save,保存文件
- 弹出Speed Generator File saving界面,勾选shape processing和error checking,然后点击ok
- 然后点击start Simulation,开始仿真
- 弹出如下界面
勾选Load into SPDSIM and simulation,启动SPDSIM仿真器进行仿真
勾选Pause 3D display for max efficiency,暂停3D显示加快仿真速度
点击ok
- 弹出SPDSIM licence选择界面,点击choose all,点击close
- 仿真进行中会有一个绿色的进度条,仿真结束需要一定的时间
- 仿真结束后,电压的2D曲线图如下,展示的是所有电压观测点的电压时域波形,可以看到vsource基本上是一条直线
- 单独查看IN0的电源噪声波形,只选中IN0
- 只勾选Vsource,可以看到负载的噪声对于Vsource还是有一些影响的,只是影响非常的微弱
- 点击View-3D view查看3D电压结果
- 3D的结果如下
- 点击右下角的distribution ,在present Distributions中选择需要观测两个平面间的电压分布,下图选择panel1-top层
- 右下角选择peak,然后点击Calculate,计算峰值电压分布
- 可以看到峰值电压达到了1.974V,相比刚才dynamic状态,电压要高出许多
- 接下来查看平面间动态电压分布动画视图,点击左下角切换回layout界面
- 将所有层面全取消勾选
- 切换回distribution界面,还是只选择plane01-top,speed拉到最大,选择dynamic,点后点击play
- 动画显示plane01和top之间电压的时域变化
- 除了可以观看,也可以见3D结果保存下来,选中其中一个平面对,比如plane01-top,右击选择Set Distribution File name
- 弹出保存界面,输入名字,比如plane01-top,然后点击保存
- 当前文件夹下方就有保存的好的DIS文件
- 保存好的DIS文件,可以加载进来,还是在distribution界面,空白处右击选择Load Distribution
注意不能加载当前存在dis文件,否则会报错
- 弹出文件选择界面,选中刚才保存好的plane01-top.DIS文件,点击打开
- 加载进来的视图如下
- 将speed拉到最大,选择dynamic,点击play,同样会以动画形式查看平面间电压的波动
- 关于为什么最后需要使能非VDD和GND的网络,是希望将这些网络对于电源地的影响考虑进去,虽然没有定义激励,不使能和使能的结果比较如下
可以看到使能后,电源的噪声幅度会更大,更接近实际情况
本例中是这个模式来观测电源的时域波形,除此之外这个模式也是可以的用来观测信号的电压时域波形的
Along with accuracy and efficiency, SPEED2000 provides an analysis flow that is particularly
valuable for design simulations that benefit from direct time domain observation. SPEED2000
can read databases from popular package and board design tools.
Chip data can also be incorporated into the same file for co-simulation. This provides an
environment for accessing the impact of noise propagation throughout the entire structure.
Circuits in the combined design are linked with SPICE circuit files.
Simulation parameters and excitation are added by the user; however, the user does not need
to create special purpose models. SPEED2000 directly provides voltage and current
waveforms.
SPEED2000 is particularly effective to be used for, but it is not limited to, the following
applications:
■ Computation of power and ground noise.
■ Determination of decoupling capacitor placement, including the number, values, and
locations of decoupling capacitors
■ Determination of frequency-dependent port parameters of packages, such as port input
impedances, S parameters, and transfer functions between different ports
■ Evaluation and design of power and ground distribution systems, including power and
ground plane arrangement, and power and ground via / pin assignment
■ Evaluation of electromagnetic coupling between different components
■ Evaluation of electromagnetic radiation from packages and printed circuit boards
■ Evaluation of signal and noise spectrum at various locations
■ Evaluation of signal and noise waveforms at various locations
■ Identification of package resonance.
SPDGEN and SPDSIM
SPEED2000 is composed of two executable modules: SPDGEN and SPDSIM.
■ SPDGEN — Provides a graphical user interface so the user can conveniently build and
modify package components and establish simulation parameters
■ SPDSIM — Provides the transient simulation engine that processes and displays the
package components. SPDSIM also provides a post processing interface so the user can
analyze, compare and print the results of package simulation
The SPDSIM simulations are entirely controlled by what the user establishes and sets up in
the SPDGEN package editor.
SPEED2000 provides powerful 3D editing functions using the SPDGEN module. Before
the.spd file (representing your package) is loaded into the SPDSIM module, the viewing and
simulation parameters need to be specified within the.spd file using the SPDGEN module.
In addition to simulation, the SPDSIM module provides a post processing interface so the
user can analyze, compare, save, export and print the results of package simulation.
■ The SPDGEN module provides the GUI-based package geometry editor and file builder,
it is used to create and edit the SPEED file (.spd) which contains package geometry and
simulation parameters
■ The SPDGEN Graphical User Interface (GUI) makes convenient “what if” analysis of a
package design possible; that is, a user can conveniently engineer a possible solution to
a problem (made apparent during the simulation) then simulate the new model to see the
results of changes made
■ The SPDSIM module loads and executes a transient simulation of the .spd file created
by SPDGEN. It should be noted that SPDSIM does not change the .spd file contents.
Use SPDGEN to select which components of a package design will be simulated