Component, Model  and Library Concepts
Summary
Article
AR0104 (v2.3) April 21, 2008
This article explains Altium Designer components, models and libraries, and their relationships. Approaches for identifying and managing component-to-library
relationships are explored, as well as the search sequence for locating models and
the options that make these searches more effective.
Components form the basic building blocks of electronic products. During the design capture and implementation process a component can be represented in different ways: as logical symbols on the s
chematic, as footprints on the PCB, as SPICE definitions for simulation, as signal integrity descriptions for analysis, and as three-dimensional descriptions for 3D component and PCB visualization. While not every one of these representations is necessary for a component, there is a minimum
definition required before a component can at least be placed into a schematic design. What makes up a starting component is established, and how adding additional properties, parameters, and models make implementing the component in various parts of the design process possible is discussed.
Components – the Basic Building Blocks
A component  is the general name given to a constituent part that can be placed into an electronic design whether it is the
schematic capture or the PCB layout. Components can have multiple representations for each of the phases of design capture, and thus may be referred to by different contextual names depending on the current implementation. Flexibility is a requirement for component definition so that all of its information and linkage can be easily adapted and transferred from one phase of design to the next.
Because electronic design begins with the schematic capture, a component has minimum requirements for placement in any schematic design – at the very least with its own name in a schematic library. It may also contain pins and graphic symbols in single or multi-part fashion, and even have alternative display options.
Once placed on the schematic design and assigned a graphical representation, the component is then more commonly called a symbol . Because it is graphical, the symbol includes drawing objects that define its physical shape and pins that define the electrical connection points, or logic . You may also hear the symbol referred to as a logical symbol  during schematic design capture.
Figure 1.  A component can have one or more component parts.
Their initial simple definition makes it easier and more flexible for components to be adapted to represent very complex electronic entities. Certain components, such as a resistor network or relay, can be drawn as a series of separate parts which can be placed independently on the
schematic. These are referred to as multi-part components  and their individual pieces are simply called parts .
The different phases of design are called domains  – these are the specific types, groups or areas of representation. In the Altium Designer environment the valid domains include PCB layout, SPICE simulation, signal integrity analysis, and 3D.
As previously mentioned, there are some distinct contextual terms used during the PCB layout and design. A footprint  describes the model that represents the component on the PCB layout. A footprint is thus a grouped set of PCB pads and component overlay shapes that define the space required to mount and connect the component on the board layout. Once mounted on a PCB, the component is then considered to be a physical  component.
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It’s worth noting that in most cases, the logical symbol also represents the physical component. When this is the case, the references for each will be the same. However, one exception is that in the case of components placed from a database library, the record in the external database represents the physical component (and the symbol is effectively a model then).
Let’s discuss in more detail the concepts of how components are defined and described, the different types of representation they can have, and how more specialized types are supported in Altium Designer.
Component, Model and Library Concepts
Component Properties
We’ve established that the symbol Array with minimal definitions and linkage
is the essential starting point for any
component in Altium Designer. This
allows for greater flexibility for the
component to be represented in
different ways later during other
parts of the design and capture
process. Altium Designer supports
different approaches to building
components that adapt to whatever
your design requirements are.
Various attributes, linkages and
descriptions can be easily defined for
any component to create unique
properties for it through the
Component Properties dialog –
allowing you to create exactly the
type of representation and
implementation needed for every
phase of your design.
Figure 2. Double-clicking on any placed component will access the Component Properties dialog where you can define specific attributes, links for libraries, graphical representations, define search locations, and much more for your components.
Component Properties dialogs will differ depending on the design editor you are using (schematic, PCB, etc.).
Component Types
Components can be built several different ways in Altium Designer. It’s worth discussing some of the standard and non-
standard types as well as multi-part components.
Common Graphic, Different Component
One Component Symbol for Each Physical Component
This type of representation is ideal for any component where the logical symbol is the same as the physical component such as
integrated circuits. The component would include the specific representation, or model (described in greater detail below) such
as the PCB footprint, simulation or 3D modelling information.
One Symbol for Graphically Equivalent Components
Sometimes components are logically equivalent but have slightly different component specifications. An example would be a
logic gate that is available in a variety of logic families, for example a 74ACT32 and a 74HC32. In this case the symbol is drawn
once, and then another name, or alias, is defined for each equivalent component required. Component aliases are added in the
Schematic Library editor panel. Component aliases can be thought of as one component, with multiple names.
One Symbol for a Type of Component
PCB components have some special considerations with respect to component types where the component may need to be
linked to multiple PCB footprints depending on the physical layout requirements of the design. An example of this would be
discrete components such as resistors where the component has a value attribute that is defined when the component is placed
on the schematic, rather than in the library.
Common Component, Different Graphics
Altium Designer supports multiple symbols for the same component. For example, you may have one client that requires their
symbols drawn using traditional drawing shapes while another requires the symbols drawn in accordance with a specific
standard. Or you may require many different symbols for the same component. You can define additional graphical
representations for a symbol that are stored with the component by adding a new mode, either from the schematic library editor
Tools menu, or by using the Mode toolbar (Figure 3).
Component, Model and Library Concepts
Figure 3. Use the Mode feature to define multiple graphical representations of the same component. The first mode is called “Normal” while subsequent modes are titled “Alternate 1”, etc.. Any mode that is created is automatically stored with the component.
Multi-part Components
In some instances it is more appropriate to represent the one physical
component using multiple symbols, for example each resistor in a resistor
network, or the coil and contacts of a relay.
Additional parts are added or removed using the commands in the library
editor Tools menu. Each part is then drawn individually, and pins are
added accordingly.
Non-standard Component Types
Not all components are destined to be mounted on the assembled PCB, not
all components are required in the Bill of Materials (BOM), and not all items
that are mounted on the PCB need to be represented on the schematic.
Altium Designer supports non-standard component types through the
Component Type property, set in the Component Properties dialog in the
library or schematic editor.
For example, the presentation and readability of your schematic might be
enhanced by including a chassis-mounted component that is wired to the PCB. If this component was not required in the PCB BOM, then the component type can be set to Graphical. A graphical component is not included during schematic electrical verification, it is not included in the BOM, nor is it checked during schematic to PCB synchronization. In this case the Component Type is set to Graphical
.
Figure 4. Setting the component type for special
component requirements. Note here that you can also
see which part you are viewing for a multi-part
component.
Another special class of component would be a test point – this component is required on both the sc
hematic and the PCB, it should be checked during design synchronization, but is not required in the BOM. In this case the Component Type is set to Standard (No BOM).
Another example of a special component kind would be a heat sink – typically it is not shown on the schematic and is not required to be checked during schematic electrical verification, but must be included in the BOM. In this case the component type is set to Mechanical.
Component Parameters
Parameters are a way of defining and associating additional textual information to the component. This can include electrical specifications (i.e., wattage or tolerance), purchasing or stock details, designer notes, or references to component datasheets. This information is included by adding parameters to the component either during component creation in the library editor; once the component has been placed on the schematic (using a DBLink file); or automatically during placement when placing from a database library (DBLib or SVNDBLib).
Adding Parameters to an Individual Component
Adding a component parameter to an individual
component is easily done by going directly
through the Component Properties dialog for that
component:
Figure 5. You can define a name and value for a component parameter and setup the graphical properties that will determine how the parameter information appears in the workspace through Component Properties.
Any parameters defined in the Parameters section are also made available in the Match By Parameters region of the Annotate dialog. This is particularly useful if you later wish to group specific parts of a multi-part component, using a unique parameter that you have defined and included for tho
se parts.
Component, Model and Library Concepts
Adding Parameters to a Component Library
While the example above shows the manual addition of parameters to an individual library compone
nt using the Component Properties  dialog (Figure 6), you may require a more streamlined approach to add parameters to a library of components. In such instances the Parameter Manager  dialog would be the better option.
Figure 6. With the schematic library still open, launch the Parameter Editor dialog from Tools  » Parameter Manager. You can then fill in parameter values for multiple components much more efficiently.
Referencing Datasheets as Parameters
There may be times when you need to access your own reference material from within a design project using a component datasheet. Altium Designer provides two options for linking from a component on the schematic sheet to reference datasheets which is established through the addition of component parameters. The first option allows you to use the F1 button to access a specific referenced document. The second option allows for multiple references and uses the right-click context menu. Single Linked Document - F1 Access
If a component includes a parameter using the system-reserved name of HelpURL , then the URL will be accessed when the F1 button is pressed while the cursor is hovering over the component or its entry in the Libraries panel. The URL can actually be a web address, a text file, or a
PDF file.
The parameter’s value can point to a document and even include a specific page number in a PDF (Figure 7).
Figure 7. Here a HelpURL parameter has been added to a schematic symbol from the Component Properties dialog. Given the value of
\Help\CR0118 FPGA Generic Library Guide.pdf#page=93 results in the referenced PDF file being opened at page 93 when the F1 button is pressed when the cursor is over the placed component.
Multiple Linked Documents – Right-click Access
This second technique enables you to define and support multiple links to one or more reference documents in a right-click context menu by pairing parameters and using the system-reserved name of ComponentLinknURL :
Parameter Name Example Parameter Value 1st  parameter ComponentLink1URL C:\MyDatasheets\XYZDatasheet.pdf 2nd  parameter ComponentLink1Description Datasheet for XYZ
1st  parameter ComponentLink2URL C:\MyDatasheets\AlternateXYZDatasheet.pdf 2nd  parameter
ComponentLink2Description
Datasheet for Alternate XYZ
Component, Model and Library Concepts
Any number of links can be defined using the same parameter pair, except with the number incremented.
When you right-click on a component that uses datasheet linking, a Reference  menu entry will appear in the Context menu, in it you will find an entry for each component link,
as shown in Figure 8.
Component-to-datasheet linkage can also be used when you are browsing components in the Libraries  panel – press F1 or right-click on the component name in the panel to access the linked documents/URLs.
For more information about adding other types of component parameters, refer to the Creating Library Components  tutorial.
Figure 8. Right-click on the placed symbol to access the datasheet links.
Models – Specialized Component Representations
Remember that domains are the type, group, or area of component representation that can be captured as part of the design process in Altium Designer. A model  thus is the implementation representation of the component that is useful for a particular domain. This could be as a footprint on the PCB, as a SPICE definition for simulation, as a suitable signal integrity description for signal integrity analysis, or as a three-dimensional model for 3D visualization in either or both the legacy 3D viewer and the DirectX-based 3D visualization engine. While a component is not required to have a
model attached to it in order to be placed in a schematic alone, it cannot be implemented in any other domains until it does.
Model Libraries  are a collection of component representations, and are described in further detail in the library section below. It’s worth explaining the fundamentals of how model mapping information is stored with the component.
Fundamentals of Model Mapping Information
At the schematic stage, the design is a collection of components that have been connected logically. To test or implement the design it needs to be transferred to another modeling domain, such as simulation, PCB layout, signal integrity analysis, etc.
Each domain needs some information about the component, and also some way to map that information to the pins of the schematic symbol. Some of this domain information resides in model files, the format of which is typically predefined. Examples of these include IBIS, MDL and CKT. Some of the information does not reside in the model files, for example the SPICE pin-mapping and net listing data must be stored and managed by the system.
All of the necessary domain information is contained within the schematic component, which stores a separate interface to each model that has been added to it. In effect,
the complete model is the combination of the model mapping information stored in the
component, and the domain modeling information stored in the model library.
Figure 9. Information on how to model the component in each domain is stored in the model
files. Here we see how the symbol hooks to the individual implementation models.

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