science

Schematic capture

Schematic capture is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Schematic capture rather than just read about it. In short: Schematic capture or schematic entry is a step in the design cycle of electronic design automation (EDA) at which the electronic diagram, or electronic schematic of the designed electronic circuit, is created by a designer. This is done interactively with the help of a schematic capture tool also known as schematic editor.

Key takeaways

Schematic capture belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Schematic capture to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Schematic capture from memory before moving on to harder problems.

Reference excerpt

Schematic capture or schematic entry is a step in the design cycle of electronic design automation (EDA) at which the electronic diagram, or electronic schematic of the designed electronic circuit, 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 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 arrays and tiny passive components – schematic capture is easier today than it has been for many years. CAD software 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 fabrication company. In past years, schematic diagrams with mostly discrete components 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 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 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 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.

Worked examples

Example 1 — a first encounter with Schematic capture

Start with the simplest possible case. Write down what Schematic capture claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Schematic capture before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Schematic capture ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Schematic capture

In research: Schematic capture appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Schematic capture in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Schematic capture is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electronic design automation, so understanding it makes those chapters shorter.
In everyday life: Look for Schematic capture outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Schematic capture in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Schematic capture means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Schematic capture out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Schematic capture in simple terms?

Why does Schematic capture matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Schematic capture?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Schematic capture.