Schematic capture
Encyclopedia
Schematic capture or schematic entry is a step in the design cycle of electronic design automation
Electronic design automation
Electronic design automation is a category of software tools for designing electronic systems such as printed circuit boards and integrated circuits...

 (EDA) at which the electronic diagram, or electronic schematic
Circuit diagram
A circuit diagram is a simplified conventional graphical representation of an electrical circuit...

 of the designed electronic circuit
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...

 is created by a designer. This is done interactively with the help of a schematic capture tool also known as schematic editor
Schematic editor
A Schematic editor is a tool for schematic capture of electrical circuits or electronic circuits.Schematic editors replaced manual drawing of schematic diagrams, but they still retain the capability of outputting schematics on specially formatted sheets...

.

The circuit design
Circuit design
The process of circuit design can cover systems ranging from complex electronic systems all the way down to the individual transistors within an integrated circuit...

 is the very 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 flow (EDA)
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...

.

Despite the complexity of modern components – huge ball grid array
Ball grid array
A ball grid array is a type of surface-mount packaging used for integrated circuits.- Description :The BGA is descended from the pin grid array , which is a package with one face covered with pins in a grid pattern. These pins conduct electrical signals from the integrated circuit to the printed...

s and tiny passive components – schematic capture is easier today than it has been for many years. CAD software
Computer-aided design
Computer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...

 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 or directly linked to a printed circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

 fabrication company.

In past years, schematic diagrams with largely discrete components
Discrete device
A discrete device is an electronic component with just one circuit element, either passive...

 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
Readability is the ease in which text can be read and understood. Various factors to measure readability have been used, such as "speed of perception," "perceptibility at a distance," "perceptibility in peripheral vision," "visibility," "the reflex blink technique," "rate of work" , "eye...

 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
Circuit design
The process of circuit design can cover systems ranging from complex electronic systems all the way down to the individual transistors within an integrated circuit...

 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
Chip carrier
A chip carrier, also known as a chip container or chip package, is a container for a transistor or an integrated circuit. The carrier usually provides metal leads, or "pins", which are sturdy enough to electrically and mechanically connect the fragile chip to a circuit board. This connection may be...

. 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
Design for manufacturability
Design for manufacturability - is the general engineering art of designing products in such a way that they are easy to manufacture. The basic idea exists in almost all engineering disciplines, but of course the details differ widely depending on the manufacturing technology...

 analysis. However, in a rapid prototyping
Rapid prototyping
Rapid prototyping is the automatic construction of physical objects using additive manufacturing technology. The first techniques for rapid prototyping became available in the late 1980s and were used to produce models and prototype parts. Today, they are used for a much wider range of applications...

 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 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.

After the circuit design
Circuit design
The process of circuit design can cover systems ranging from complex electronic systems all the way down to the individual transistors within an integrated circuit...

 is captured in a schematic, then the PCB layout can begin.

Schematic Capture Tips

To make schematics easier to read there are a few tips that can increase organization and readability.
  • Schematics should read left to right, just like a book. Generally, inputs on the left, outputs on the right.
  • Naming signals / nets will dramatically increase the readability and traceability of your schematics. It will be a great help during the pcb design phase of your project.
  • No 4-way ties. A 4-way tie can cause confusion and should be avoided at all times (This 'tip' is often contended among design professionals).
  • Break the schematic into logical building blocks. This is easily accomplished with multiple pages, each having a dedicated functionality.
  • Use all capital letters as much as possible, especially for small text such as net names. This improves legibility, and is required by most drafting standards.
  • To maximize portability, net names should consist of letters, numbers, and underscores. Use of characters such as spaces, pluses or minuses, or case sensitive names (i.e. two or more names who only differ in case) is discouraged, as it can cause subtle problems when exporting a netlist for simulation or layout. For example, net names in Verilog cannot have spaces; a netlist export tool would have to "escape" these characters to allow a Verilog simulation, which could lead to confusion if there are later errors referencing these nets.

See also

  • Comparison of EDA software
    Comparison of EDA software
    Comparison of Electronic Design Automation software-Free and Open Source Software :-Proprietary software:-Comparison of EDA packages:Note: ODB++ support is drawn partly from lists by Artwork Conversion Software and Mentor Graphics...


Individual products

  • Altium – Providers of Altium Designer (formerly Protel) and P-CAD (retired June 30, 2008).
  • Autotrax
    Autotrax
    AutoTRAX EDA is a Windows XP/Vista schematic design/ PCB layout program with built in Spice simulator and 3D part and board visualization. It is not to be confused with the simple PCB CAD package originally developed by Protel in the 1980s and 1990s and which is still available as a free download...

     – EDA/DEX is a Windows XP/Vista/7 schematic capture / PCB design layout program with built in Spice simulator and 3D part and board visualization.
  • DipTrace
    DipTrace
    DipTrace is EDA software for creating schematic diagrams and printed circuit boards. The first version of DipTrace was released in August, 2004. The latest version as of September 2011 is DipTrace version 2.2. Interface has been translated to many languages and new language can be added by user....

     – mid-range Schematic Capture and PCB Layout software that has a free version.
  • Edwinxp
    Edwinxp
    EDWinXP or Electronic Design for Windows is a commercially available PCB design integrated CAD/CAE package. An electronic design engineer can use the computerized tools provided in EDWinXP to create an electronic circuit, design the PCB and fabricate PCBs...

     – Totally Integrated Schematic Capture, Simulation and PCB design software.
  • Electronics Workbench
    Electronics Workbench
    The National Instruments Electronics Workbench Group is responsible for innovating the electronic circuit design software NI Multisim and NI Ultiboard, which was previously a Canada-based company that first produced MultiSIM, and integrated ULTIboard with it....

     – Schematic Capture, Simulation and PCB design software suite.
  • Multisim – Schematic Capture and SPICE Simulation software.
  • Cadsoft EAGLE
    Eagle (program)
    EAGLE by Cadsoft is a flexible and expandable EDA schematic capture, PCB layout, autorouter and CAM program widely used since 1988.- Schematic capture :...

     – Very capable mid-range Schematic Capture and PCB Layout software that has a free version.
  • Kicad
    Kicad
    KiCad is an open source software suite for electronic design automation . It facilitates the design of schematics for electronic circuits and their conversion to PCBs design. KiCad was developed by Jean-Pierre Charras, and features an integrated environment for schematic capture and PCB layout...

     – open source schematic capture and PCB design software suite
  • OrCAD
    OrCAD
    OrCAD is a proprietary software tool suite used primarily for electronic design automation. The software is used mainly to create electronic prints for manufacturing of printed circuit boards, by electronic design engineers and electronic technicians to manufacture electronic schematics.The name...

     – Full-featured commercial Schematic Capture and PCB layout.
  • TARGET 3001!
    TARGET 3001!
    TARGET 3001! is a CAD program for EDA and PCB design, developed by Ing.-Buero Friedrich in Germany. It supports the design of electronic schematics, PCBs, and device front panels...

     – mid-range Schematic Capture software that has a free version.
  • gEDA
    GEDA
    The term gEDA refers to two things:# A set of software applications used for electronic design released under the GPL. As such, gEDA is an ECAD or EDA application suite. gEDA is mostly oriented towards printed circuit board design...

     – open source schematic capture using gschem, simulation, and PCB design software suite
  • The Electric VLSI Design System
    Electric (software)
    The Electric VLSI Design System is an EDA tool written by Steven M. Rubin.Electric is used to draw schematics and to do integrated circuit layout.It can also handle hardware description languages such as VHDL and Verilog....


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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