Schematic capture or schematic entry is a step in the
design cycle
A decision cycle or decision loop is a sequence of steps used by an entity on a repeated basis to Decision making, reach and implement decisions and to learn from the results. The "decision cycle" phrase has a history of use to broadly categorize v ...
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 Electronics, electronic systems such as integrated circuits and printed circuit boards. The tools wo ...
(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 Conductive trace, traces through which electric current can flow. It is a t ...
, is created by a designer. This is done
interactively with the help of a schematic capture tool also known as
schematic editor
A schematic, or schematic diagram, is a designed representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the sc ...
.
The
circuit design
In electrical engineering, 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 pl ...
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
Design flows are the explicit combination of electronic design automation tools to accomplish the design of an integrated circuit. Moore's law has driven the entire IC implementation RTL to GDSII design flows from one which uses primarily sta ...
.
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.
CAD software
Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve c ...
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 and view the source code, design documents, or content of the product. The open source model is a decentrali ...
or directly linked to a
printed circuit board
A printed circuit board (PCB), also called printed wiring board (PWB), is a Lamination, laminated sandwich structure of electrical conduction, conductive and Insulator (electricity), insulating layers, each with a pattern of traces, planes ...
fabrication company.
In past years, schematic diagrams with mostly
discrete components
An electronic component is any basic discrete electronic device or physical entity part of an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular f ...
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. The concept exists in both natural language and programming languages though in different forms. In natural language, the readability of text depends on its content ( ...
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
In electrical engineering, 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 pl ...
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 engineering, debugging is the process of finding the root cause, workarounds, and possible fixes for bugs.
For software, debugging tactics can involve interactive debugging, control flow analysis, log file analysis, monitoring at the ap ...
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
*
Comparison of EDA software
This page is a comparison of electronic design automation (EDA) software which is used today to design the near totality of electronic devices. Modern electronic devices are too complex to be designed without the help of a computer. Electronic dev ...
Further reading
*
References
{{reflist
Electronic design automation