Schematic capture or schematic entry is a step in the design cycle of
electronic design automation
Electronic design automation (EDA), also referred to as electronic computer-aided design (ECAD), is a category of software tools for designing electronic systems such as integrated circuits and printed circuit boards. The tools work togeth ...
(EDA) at which the electronic diagram, or
electronic schematic of the designed
electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electric ...
is created by a designer. This is done
interactively with the help of a schematic capture tool also known as
schematic editor.
The
circuit design
The process of circuit design can cover systems ranging from complex electronic systems down to the individual transistors within an integrated circuit. One person can often do the design process without needing a planned or structured design ...
is the first step of actual design of an electronic circuit. Typically sketches are drawn on paper, and then entered into a computer using a schematic editor. Therefore schematic entry is said to be a
front-end operation of several others in the
design flow.
Despite the complexity of modern components – huge
ball grid array
A ball grid array (BGA) is a type of surface-mount packaging (a chip carrier) used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors. A BGA can provide more interconnection pins than can be pu ...
s and tiny passive components – schematic capture is easier today than it has been for many years.
is easier to use and is available in full-featured expensive packages, very capable mid-range packages that sometimes have free versions and completely free versions that are either
open source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized so ...
or directly linked to a
printed circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...
fabrication company.
In past years, schematic diagrams with mostly
discrete components
An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are no ...
were fairly readable. However, with the newer high pin-count parts and with the almost universal use of standard letter or A4 sized paper, schematics have become less so. Many times, there will be a single large part on a page with nothing but pin reference keys to connect it to other pages.
Readability
Readability is the ease with which a reader can understand a written text. In natural language, the readability of text depends on its content (the complexity of its vocabulary and syntax) and its presentation (such as typographic aspects that ...
levels can be enhanced by using buses and superbuses, related pins can be connected into a common bus and routed to other pages. Buses don't need to be just the traditional address or data bus directly linked pins. A bus grouping can also be used for related uses, such as all analog input or all communications related pin functions.
Other considerations
After the
circuit design
The process of circuit design can cover systems ranging from complex electronic systems down to the individual transistors within an integrated circuit. One person can often do the design process without needing a planned or structured design ...
is captured in a schematic, most EDA tools allow the design to be simulated.
Schematic capture involves not only entering the circuits into the CAD system, but also generally calls for decisions that may seem more appropriate for later in the design, such as
package choice. Although you may be able to change the package later, many PCB CAD systems ask you to choose both the part and package when placing it into the schematic capture program.
This also brings into play such considerations as prototyping and assembly. In a high-volume assembly environment, there will be plenty of opportunities for
DFM analysis. However, in a
rapid prototyping
Rapid prototyping is a group of techniques used to quickly fabricate a scale model of a physical part or assembly using three-dimensional computer aided design (CAD) data.
Construction of the part or assembly is usually done using 3D printing ...
environment such as at assembly houses specializing in low-volume/high-mix and quick turnaround times, the
pick and place machines are programmed directly from the board layout files. Careful package selection during schematic capture will save time during the assembly and
debug
In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems.
Debugging tactics can involve i ...
process.
With new parts, the CAD system may not have your chosen component in its parts library, so you may need to create the parts library yourself. Again, you may at the time not be overly concerned with the package, but careful creation of the part library will save time and risk later.
See also
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Comparison of EDA software
Further reading
*
References
{{reflist
Electronic design automation