In the speech of people associated with electronics, there is a phrase: “You need to look at the datasheet.” What did you mean and where can I get the notorious datasheet?
The word is borrowed from English and is originally written as datasheet. If you translate it into Russian, it literally turns out to be “a sheet of information.” The document is compiled on various devices and electronic components. Therefore, it is correct to say that a datasheet is technical documentation prepared by the manufacturer.
Features of reading circuits
In circuit diagrams, conductors (or tracks) are indicated by lines.
This designates conductors that intersect, but they do not have a common connection and are not electrically connected to each other. And this is what they look like if there is a connection between them. The black dot is a node in the circuit. A node is a connection of several conductors or parts together. They are electrically connected to each other.
Common point
Beginner radio amateurs often have a question: what is this symbol on the diagram?
This is the common point (GND, ground). Previously, it was called the common wire. This is how a single power wire is designated. Usually this is a minus of nutrition. Previously, in the diagrams they could make the common wire and the power plus. In this case, the diagram without a common point would look like this:
A common point with unipolar power supply looks visually better and more compact than if you simply make a single line between them.
It is also called a common point because any other points on the diagrams can be measured relative to it. For example, place the multimeter probe on a common point, and with the second probe you can check any part of the circuit in the diagram.
Why can it be called ground (GND)? Previously, the chassis of the device body could be used as a common wire. This has caused confusion between grounding and earth. It is interpreted in the context of the schema. The circuit that was discussed above - the common point (ground) is simply a minus of the power supply. Another thing is bipolar current sources and grounding.
Bipolar power supply and common point
In a bipolar supply, the common point is the middle contact between plus and minus.
Grounding
An example of grounding would be a filter in computer power supplies.
From the capacitor filter, noise goes to the power supply housing. This is grounding. And from the power supply they must go into the outlet if you have a ground connection, otherwise the body of the power supply itself may be energized. The currents there are not large, they are not life-threatening. This is done to reduce impulse noise in the power supply and safety.
Sometimes in power supplies, instead of the housing, noise from the capacitor goes to a common point. It all depends on the design and circuitry. In this case, there will be more interference than with grounding.
In general, there are different grounding connections on the diagrams. For example, in digital technology, analog ground is separated from digital ground. so as not to disrupt the operating modes of the circuit. Pulse noise can affect the analog part of the circuit.
Contents of the document
Quite often, users ask about the datasheet: “What is it and how to read it?” While the first issue has been addressed, the second remains to be explored.
Electronics engineers refer to the following sections of this document.
- Basement.
It describes the purpose of each pin of the chip or transistor. The designer is interested in contacts marked Vcc and GND. The first is intended for supplying power voltage (usually +5 V), the second is for connecting the ground. Microcontrollers can have many of these pins. Their location depends on the housing type (PDIP / TQFP / MLF).
- Block diagram
Shows the internal contents of a component. For example, for a microcontroller, the memory, clock, and I/O ports are shown.
- Schematic electrical diagram).
Defines the typical connection of the device. In practice, the circuits differ from those given in the documentation, since in each specific case a microcircuit or transistor is part of a complex electronic device in which all its components must be taken into account.
- Temperature and electrical parameters.
These values are presented in the form of graphs showing the dependence of one parameter on another.
Ratings of radio components
In general, there are disagreements in this regard. According to GOST at the moment, the nominal values of parts are not indicated on circuit diagrams. This is done in order not to clutter the diagram with information.
The circuit diagram is accompanied by a list of parts, wiring and structural diagrams, as well as a printed circuit board.
There is another generally accepted standard. The diagrams indicate the ratings of some parts and their operating voltages.
For example, in this circuit there are two resistors.
By default, resistance without a prefix is written only as a number. R2 has a resistance of 220 Ohms. And R3 has a letter after the number. The resistance of this resistor reads 2.2k ohms (2,200 ohms).
Consider two capacitors in the diagram.
In this case, C5 is a non-polar capacitor with a capacitance of 0.01 µF. Microfarads can be designated either uF or uF. And capacitor C6 is polar and electrolytic. This is indicated by the plus sign near the UGO. Capacitance C6 is 470 μF. The rated operating voltage is indicated in volts. Here for C6 it is 16 V.
Nanofarads are denoted as nF.
If there is no microfarad (uF) or nanofarad (nF) prefix on the circuit, then the capacitance of this capacitor is measured in picofarads (pF, pF). This condition is not common, so carefully study the diagram you are about to read or assemble. There are few capacitances in farads (F), so µF, nF and pF are used.
What is a datasheet and why is it needed?
Datasheet is a technical specification that provides complete information about a radio component. All technical information, basic connection diagram, parameters and types of housings are indicated in this document.
Datasheets come in different languages, mostly in English. There are also translated versions.
Documentation for the NE555 chip. The body and appearance of the part are drawn.
The microcircuit, its parameters and operating conditions are described in detail here.
Such documentation is available for any detail. This is very convenient and informative, especially when searching for analogues. And with the help of the Internet, searching for analogue parts or diagrams has become even easier.
The datasheet also allows you to identify an unknown part or microcircuit. Just write its name in a search engine, add the word datasheet, and all the documentation will be in the search results.
Search datasheets for electronic components
It may become clear what the chip datasheet is after it is opened. But the question is: “Where can I get it?”
In the Soviet Union, documentation was standardized. If you needed to find information about a transistor or microcircuit, you needed to get the appropriate manual. Today there is no need for reference books. They have been replaced by search engines - just type in the word datasheet and indicate the name of the required device. The second option to get a datasheet is to go to the site where the documentation is collected and conduct a search on it.
Component specifications are provided as pdf files. You can open them directly in the browser.
How to learn to read circuit diagrams
There are really only a few ways. This is theory and practice. If you learn the designation of radio components, this does not mean that you have learned circuit design. It's like learning your ABC's, but without grammar and practice you won't learn the language.
Theory is circuit design, books, a description of the principle of operation of the circuit. Practice involves assembling devices, repairing and soldering.
For example, a simple amplifier circuit with one transistor.
Input X1 plus (left or right channel), X2 minus. The sound signal is sent to electrolytic capacitor C1. It protects transistor VT1 from short circuiting, since transistor VT1 is constantly open using a voltage divider across R1 and R2. The voltage divider sets the operating point at the base of transistor VT1, and the transistor does not distort the input signal. Resistor R3 and capacitor C2, which are connected to the emitter of transistor VT1, perform the function of thermal stabilization of the operating point as the temperature of the transistor increases. Electrolytic capacitor C3 accumulates and filters the supply voltage. The BF1 dynamic head serves as an audio signal output.
Is it possible to understand this only by learning the designations of radio components without circuit design and theory? Unlikely.
The situation is even more complicated with digital technology.
What kind of microcontroller is this, what functions does it perform, what firmware and what fuses are installed in it? And the second microcircuit, what amplifier is it? Without datasheets and a description of the circuit, it will not be possible to understand its operation.
Study circuit design, theory and practice. Simply learning the names of the parts will not help you understand the circuitry. The designation of radio components can be learned on its own with practice and accumulation of knowledge. It all depends on the chosen industry. Signalmen have one circuit design, mobile equipment repairmen have another. And those who deal with sound will not really understand electricians. As well as vice versa. To understand another industry, its circuitry and operating principles, you need to immerse yourself in it.
Circuit diagrams are a kind of language that has different dialects.
Therefore, one should not create illusions. Study circuit design and assemble circuits.
Schematic diagrams help to assemble devices, and when studying the theory, to understand the operation of the device. Without knowledge and experience, a diagram is just a diagram.
First page of the datasheet
Once the document has been downloaded to your computer, you need to open the spreadsheet. What does it contain, what should you look for first?
You should start from the first page. It contains information that highlights the uniqueness of a particular device, for example, wide frequency range, low power consumption, low dark current.
The technical specifications home page contains:
- pin configuration in the form of a table or diagram).
- description (description/general description);
- properties of components (characteristics);
It should be noted that the information provided is not always sufficient, so you should not trust it completely. Answers to emerging questions should be sought in the relevant sections of the document. The purpose of the first page is to give an introduction, that is, to tell what it is about.
The transistor passport is small compared to a similar document for microcircuits, so information about its parameters and connections is immediately indicated on the first page.
