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Parent page: High Speed Design. With increasing device switching speeds, controlled impedance routing has become a hot topic for the digital designer. This article introduces how you can use the Signal Integrity analysis engine to match component impedances and the controlled impedance routing capabilities in the PCB editor.
There is a saying in engineering circles – there are only two kinds of electronics engineers working in digital design: those who have had signal integrity problems, and those who will.
Not so many years ago the term signal integrity was one for the specialist and you only had to deal with it on high-speed designs. However, the device switching speeds in those high-speed designs are no longer anything special, in fact, they are rapidly becoming the norm. As improving integrated circuit technology drives the size of the transistor down, the speeds at which they can switch goes up.
And it is this switching speed that affects the integrity of digital altium designer 17 highlight net free. Thankfully altium designer 17 highlight net free potential signal altium designer 17 highlight net free issues can be avoided by following good design principles and implementing the design as a controlled impedance board. Achieving this does require specific design tool capabilities – you need analysis tools that can detect nets with potential ringing and reflection issues, and board design tools that allow you to achieve the correct routing impedances.
This article will help you understand what causes signal integrity issues and if your board is likely to suffer from them. Controlled Impedance Routing: configuring the routing widths and clearances, as well as the material properties and dimensions, to deliver the required routing impedance s. As device switching speeds increase, so too do the demands продолжить чтение the printed circuit board designer and the fabricator.
As the length of the signal switching edge becomes shorter than the length of the PCB trace that carries it, altium designer 17 highlight net free trace has to be treated as part of the circuit. That trace has an impedance, which is referred to as the characteristic impedance Zo. The best way to manage the impact of these additional circuit elements is to design the trace routing so that the characteristic impedance is consistent over the length – a technique called controlled impedance routing.
The Simbeor impedance calculator calculates the width s required to achieve the specified impedance. In an ideal situation, all of Вам windows 10 home enterprise pro free download ощущение energy that comes out of a component output pin would be coupled into the connected track on the PCB, flow through the PCB routing to the load input pin at the other end, and be absorbed by that load.
If all the energy is not absorbed by the load then the leftover energy can be reflected back into the PCB routing, flowing to the source output pin. This reflected energy can interact with the original signal, adding to and subtracting from it depending on the polarity of the energyresulting in ringing.
If the ringing is large enough, it will affect the integrity of the signal, resulting in unpredictable, erroneous circuit behavior. So how do you know if this might occur? If the source pin is able to complete its edge transition before the signal reaches the load pin, the conditions exist altium designer 17 highlight net free your design to be impacted by reflected energy.
If the source pin has a 1 nSec rise time, a route longer than. If your antivirus for windows 10 have this sort of rise time and you know you will have routing of this sort of length, then you might end up with signal integrity issues on the PCB. The speed at which the electrical energy can travel along the route is altium designer 17 highlight net free as the propagation velocity, where:. How do you avoid the situation where there is energy being reflected back and forth between the source and the load?
You avoid it by matching the impedances. Impedance matching ensures that all the energy altium designer 17 highlight net free coupled from the source into the routing, and then from the routing into the load. Routing the board with regard to the impedance is referred to as controlled impedance routing or another way of saying it is that a board where impedances have been managed is called a controlled impedance PCB.
There are two distinct elements to achieving impedance matching: the first is matching the components; the second is routing the board to give the required impedance. You cannot achieve a controlled impedance PCB with routing alone. First, you must check, and if necessary, match the impedances of the components. Ideally, you want to detect nets that could have potential signal integrity issues during the design capture phase so that any additional termination components can be included before the board design process starts.
Since output pins are low impedance and input pins are high impedance, it is likely that you will need to add termination components to the design to achieve impedance matching. You can perform a signal integrity analysis on your design at the schematic capture stage.
When you run the Tools » Signal Integrity command the Errors or Warnings dialog will often appear, indicating that not all components have signal integrity models assigned.
The Signal Integrity analysis engine will automatically select default models based on the component designators, click Continue to use the defaults or Model Assignments to examine and change the models.
The Signal Integrity analysis engine will use defaults for the required impedance and average track length. It will also use default values for the signal stimulus the properties of the theoretical signal that is injected. These defaults can be configured once the Signal Integrity panel has opened, via the panel’s Menu button » Setup Options command.
Note that the Signal Integrity analysis engine requires power planes for the reference planes, it is not able to use a signal layer covered by a polygon. The Signal Integrity analysis engine installs as a System Altium designer 17 highlight net free.
If it is not currently installed, click the Configure button to install it. When the Tools » Signal Integrity command is run the design is analyzed, any potential problem nets are identified in the Signal Integrity panel, as shown below. Testing the design for potential signal integrity issues during design capture. From the panel, you can perform a reflection analysis on a selected net or nets. On the left is the analysis results for all nets in the design, select a net and click the button or double-click a net name to transfer that net to the Net field on the right of the panel, where you can perform a detailed analysis of altium designer 17 highlight net free net, including:.
The panel allows you to experiment with possible termination configurations and values. Note that the Termination region of the Signal Integrity panel shown in the image above has the Serial Res option enabled. The section of the panel below that shows a series termination resistor. This is where you define the minimum and maximum theoretical series termination resistance values that will be used for the reflection analysis disable the Suggest checkbox to enter your own values.
The images below show two graphs of the results at the input pin of the altium designer 17 highlight net free selected in the previous panel image. The first graph is the input pin in the net without termination; the second graph shows six sweeps, one for the original unterminated net, then five sweeps with the theoretical series termination resistance included at the source pin.
The five passes first pass at 20 ohms, last pass at 60 ohms are listed on the right-hand side of the graph. Clicking on each label highlights that result and displays the theoretical termination resistance value at the bottom right. For this net, a series termination resistance of 40 ohms would produce the graph selected in the image on the right.
The graph on the left shows the reflection analysis of a net altium designer 17 highlight net free potential signal integrity issues; the graph on the right is the same net with a theoretical series termination resistor of approximately 40 ohms added. To hide a floating panel, press F4 when the panel is active the caption bar is colored. Press F4 to restore the display of the panel.
The second altium designer 17 highlight net free of achieving a controlled impedance PCB is to route the board so that the tracks are a defined impedance. There are a number of factors that influence the impedance altium designer 17 highlight net free your signal routing, including the dimensions of altium designer 17 highlight net free routes and the properties of the materials used to fabricate the PCB. Simbeor’s model accuracy is validated through the use of advanced algorithms for 3D full wave analysis, benchmarking, and experimental validation.
The Simbeor engine supports all modern board structures and materials. The Simberian site also includes an extensive library of application notes and papers published by Simberian’s principal developer, Yuriy Shlepnev, as well as papers written in collaboration with other leading industry and academic researchers. Simbeor SFS is an advanced quasi-static 2D field solver based on Method of Moments, which has been validated by convergence, comparisons, and measurements.
The solver meshes dielectric and conductor boundaries and solves corresponding equations to build frequency-dependent RLGC matrices for the Telegraph equations. Simbeor SFS is not a full-wave solver as this is altium designer 17 highlight net free needed to evaluate the impedance, delay, or attenuation in PCB interconnects, because of the quasi-TEM nature of the waves propagating there. Such waves can be accurately simulated with RLGC parameters extracted with a quasi-static 2D field solver. A unique property of the Simbeor SFS solver is that it supports conductor roughness models.
Note that it does not support a multi-layered conductor model platingand the roughness is common for all conductors. The solver is quasi-static because the solution does not include the high-frequency dispersion that takes place in microstrip lines higher concentration of fields in a dielectric with higher dielectric constant at high frequencies.
Controlled Impedance routing is all about configuring the dimensions of the routes and the properties of the board materials to deliver a specific impedance. The Layer Stack Manager opens in a document editor, in the same way as a schematic sheet, the PCB, and other altium designer 17 highlight net free types do.
The trace width required to deliver a specific impedance is calculated as part of the impedance profile, configured in the Impedance tab of the Layer Stack Manager. When these are correctly configured, the impedance calculator has sufficient information to calculate the:. To improve calculation speeds, impedance profiles are calculated in separate threads when available. The calculated values are displayed in the Transmission Line section of the Properties panelwhen the Impedance tab is selected in the Layer Stack Manageras shown below.
Main article: Defining the Layer Stack. The copper and dielectric fabrication layers are configured on the Stackup tab of the Layer Stack Altium designer 17 highlight net free. A fundamental requirement for controlling the impedance is to include a signal return path below each signal path. The Simbeor SI engine supports both plane layers, and signal layers covered by a polygon. These return-path layers should be distributed through the board stackup.
Ideally, they are arranged so that there is at least one return-path layer adjacent to each signal layer that is carrying controlled impedance routing.
The adjacent return-path layer provides the signal return path, and for reasons that will not be covered here, does so regardless of the DC voltage distributed by that plane.
The return path current flowing through the plane will attempt to microsoft 2013 professional iso free download the same physical path as the route on the signal layer, so it is important to avoid introducing discontinuities, altium designer 17 highlight net free as a split or cutout in the return-path layer underneath any critical signal routing. As well as selecting a suitable order for signal and plane layers, you also need to define the material properties of each layer, including:.
These values, and the routing width, all contribute to the final impedance. Achieving the required impedance then altium designer 17 highlight net free a process of tuning all these values. Keep in mind that possible copper and dielectric thickness values may also be limited, determined by the materials available from your PCB fabricator. To configure the layer stack for controlled impedance routing, switch to the Layer Stack Manager’s Impedance tab where you can add and configure an impedance profile.
From the target impedance and target tolerance, the software calculates the Trace Width. It is not uncommon that the calculated trace width will be a value that cannot be ordered, for example 0. The fabricator will advise what material thicknesses are available and what precision they can achieve for trace widths. Then it altium designer 17 highlight net free a process of starting at the desired values, then testing the impact on the calculated impedance values when the dimensions are adjusted to what is available.
To support this process of testing and tuning the settings, the impedance calculators support forward and reverse impedance calculations. The default mode is forward enter the impedance, the software calculates the width. The icon indicates the calculated variable. To reverse the calculation and explore different trace widths for the selected layer, type in the new Width W1 value and press Enter on the keyboard.
Altium designer 17 highlight net free.Keeping the Schematics & PCB Synchronized in Altium Designer
If changes are required, they can easily be applied to both your schematic and PCB. The list of nets can be sorted by clicking on any of the column headings, including the enable Color Override checkbox column. Schematic example with a highlighted net. C , then D. Distribute selected objects equally in vertical plane. Post as a guest Name.
Altium designer 17 highlight net free
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