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How to Accurately Determine Whether an Integrated Circuit in an Electronic Circuit is Working Properly?

Author: Apogeeweb
Date: 23 Aug 2018
 19973
ic test

Introduction

How to accurately determine whether the integrated circuit IC in the circuit is working is an important part of repairing TV, audio, and video equipment. This article introduces the specific judgment method, the following video shows how to test IC chips with a multimeter.

How To Test IC Chips by using Multimeter (IC 6283)

Catalog

Introduction

Catalog

I How Does IC Work?

II Two General Methods for Checking ICs in a Circuit

2.1 DC Working Voltage Measurement 

2.2 AC Voltage Measurement

III FAQ

I How Does IC Work?

An integrated circuit  (hereinafter referred to as IC ) is an advanced microelectronic device that integrates many microelectronic devices on a chip. Silicon-based materials are commonly used, N-type and P-type semiconductors and P-N junctions are formed by diffusion or permeation techniques on the device. 

 

An IC is a semiconductor integrated circuit, that is, a semiconductor material is used as a substrate, two or more components which including at least one active component and some or all of the interconnections are integrated with the substrate or on the substrate, to perform as intermediate or final products of electronic functions.

IC chip

II Two General Methods for Checking ICs in a Circuit

After understanding the working principle of the IC, it is necessary to go through the following steps to accurately determine whether the IC in the electronic circuit is working properly.

 

First, we must master the purpose of the IC in the circuit and its internal structure principle and main electrical characteristics, etc., and analyze the internal circuit schematic diagram if necessary. In addition to these, if there are DC voltage, waveform, and the forward and reverse resistance values of each pin corresponding to the ground, then it provides more favorable conditions for pre-inspection judgment.

 

Then judge the part according to the fault phenomenon, and find out the faulty component according to the location. Sometimes a variety of judgment methods are needed to prove whether the device is indeed damaged. 

 

(1) Judging the IC in the circuit when it is not soldered to the printed circuit board. In this method, it is difficult to determine the quality of the IC in the circuit without special equipment. Generally, the DC resistance method can be used to measure the forward and reverse resistance values of each pin corresponding to the ground and then compared with an intact integrated circuit. It is also possible to use an alternative method to insert a suspicious IC into the position of the same type of IC as a normal device, to determine its quality. Of course, it is more assured to use the integrated circuit tester to quantitatively check the main parameters if the condition allows.

 

(2) Online checking and judging, which means to judge the integrated circuit connected to the printed circuit board. Online judgment is the most practical method for overhauling integrated circuits in home appliances. The following is a description of several situations:

2.1 DC Working Voltage Measurement 

This method is mainly to measure the DC working voltage value of each pin corresponding to the ground, then compares with the nominal value, according to this to judge the quality of the integrated circuit. Using the voltage measurement method to judge the quality of an integrated circuit is one of the most commonly used methods in maintenance, but it is necessary to pay attention to distinguishing non-faulty voltage errors.

 

When measuring the DC working voltage of each pin of the integrated circuit, if the voltage of the individual pin is inconsistent with the voltage value indicated in the schematic or maintenance technical data, do not rush to conclude that the integrated circuit is damaged. The following factors should be excluded first.

 

(1) Check the reliability of provided nominal voltage

Because the values on some of the instructions and schematics and other data are quite different from the actual voltage, and sometimes even wrong. So, you should find more relevant data for comparison. If necessary, analyze the internal schematic diagram and peripheral circuits and then make theoretical calculations or estimates to prove whether the voltage is wrong or not.

 

(2) Distinguish the provided rated voltage and working voltage 

Because the individual pins of the integrated block change significantly with the injection signal, you can change the position of the band or the record switch at this time, and then observe whether the voltage is normal. If the voltage is normal, it means the nominal voltage is a certain operating voltage, and the working voltage is in terms of a specific condition, that is, different working states have different measured voltages.

 

(3) Pay attention to the change of the pin voltage caused by the variable components of the peripheral circuit.

When the measured voltage does not match the nominal voltage, it may be because a single pin or a peripheral circuit associated with the pin is connected to a variable potentiometer or switch.  These potentiometers and switches are located at different positions, and the pin voltages are significantly different. Therefore, when a voltage difference between a pin occurs, considering the position of the pin or the potentiometer and switch associated with the pin. Pins can be rotated or pulled to see if the pin voltage is near the nominal value.

 

(4) Prevent errors due to measurement

Errors may occur due to different internal resistance of the multimeter or different DC voltage levels. In general, the DC voltages are tested with test instruments with internal resistance greater than 20KΩ/V. When using the multimeter with internal resistance less than 20KΩ/V, the measured result will be lower than the originally marked voltage. In addition, it should also be noted that the voltage measured on different voltage levels will be different, especially when the large-range files are used, the deviation effect is more significant.

multimeter

 

(5) Judging the importance of the pin voltage to the normal operation of the IC

When the measured voltage of a pin does not match the normal value, in order to judge whether the IC is good or bad, the analysis should be based on whether the pin voltage is operating normally, an important influence on the change in the voltage of the IC and the corresponding other pins.

 

(6) Checking the IC pin voltage

If the voltage of each pin of the IC is normal, the IC is generally considered to be normal. If the voltage of the pin of the IC is abnormal, it should start from the maximum deviation from the normal value. And the imported pumps should check whether the external components are faulty. If there is no fault, the IC is likely to be damaged.

 

For example, in a TV set, the voltage of each pin of the IC is different when there is no signal. If the pin voltage that should not change is found to vary greatly, and the one should change is always stable, the IC can be determined to be damaged; in a video recorder, the voltage of each pin of the IC is different under different working modes. In this case, the judgment of the IC should be more cautious.

 

The above points are that the IC does not have a fault in the circuit, and the measured result is different from the nominal value for some reason. Therefore, a test condition should be specified when performing integrated block DC voltage or DC resistance test, especially when recording measured empirical data. Usually, each potentiometer is rotated to the middle position of the machine, and the signal source adopts the standard signal under a certain field strength.

 

Of course, if the position of each function switch can be recorded again, it is more representative. If the above-mentioned factors are excluded and the measured individual pin voltages are still not in the nominal value, the reason should be further analyzed, but there are two possibilities. One is caused by the failure of the integrated circuit itself. The other is caused by the peripheral circuit of the integrated block. Identifying these two sources of faults is also the key to repair IC home appliances.

2.2 AC Voltage Measurement

In order to grasp the changes of the IC AC signal, the AC operating voltage of the IC can be approximated by a multimeter with a dB plughole. When testing, the multimeter is placed in the AC voltage block, and the positive pen is inserted into the dB plughole. For a multimeter without a dB plughole, it is necessary to connect a 0.1 to 0.5 uF DC blocking capacitor in series with the positive pen. This method is applicable to ICs with relatively low operating frequency, such as video amplification stages and field scanning circuits. Since the natural frequencies of these circuits are different and the waveforms are different, the measured data is an approximation or as a presence or absence.

 AC voltage measurement principle

AC voltage measurement principle circuit diagram

 

 

III FAQ

1. What is in an integrated circuit?

An integrated circuit (IC), sometimes called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated. An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor.

 

2. How does an integrated circuit work?

Integrated circuits are a combination of diodes, microprocessors, and transistors in a minimized form on a wafer made of silicon. ... Transistors – These components are used to store voltages or circuit stabilizers. They can be utilized to amplify the given signal and used as switches working in digital circuits.

 

3. What is the main function of an integrated circuit?

The function of an integrated circuit (IC) is to be a single component that can perform high-level tasks such as amplification, signal processing, or even sophisticated digital calculations as in the case of microprocessors. Few electronic circuits do not use an IC or a chip or microchip.

 

4. What are the types of integrated circuits?

• Thin and thick film ICs.

• Monolithic ICs.

• Hybrid or multichip ICs.

 

5. What are the benefits of integrated circuits?

• The entire physical size of IC is extremely small than that of the discrete circuits.

• The weight of an IC is very less as compared to entire discrete circuits.

• It's more reliable.

• Because of their smaller size it has lower power consumption.

• It can easily replace but it can hardly repair, in case of failure.

 

6. How do you read an integrated circuit?

Read the serial number from the top side of the IC. The top side of the IC is facing up when the chip is standing on its pins. You may require a magnifying glass while reading the IC serial information. Open your Internet browser and enter the IC's serial number into either the Google or Yahoo search engines.

 

7. What is the disadvantage of an integrated circuit?

Disadvantages of ICs: If one component in an integrated circuit fails, it means the whole circuit has to be replaced. It is difficult to be achieved a low-temperature coefficient. It can be handled an only a limited amount of power.

 

8. What is the difference between analog and digital IC?

Analog Circuits and Digital Circuits are a classic way of differentiating between two types of electronic circuits based on the signals they process. To put it in simple words, Analog Circuits deal with continuous analog signals whereas Digital Circuits deal with discrete digital signals.

 

9. Where are integrated circuits used?

ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs.

 

10. Are integrated circuits digital or analog?

Integrated circuits (ICs) are generally classified as digital (e.g. a microprocessor) or analog (e.g. an operational amplifier).

 

 

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