One, direct substitution

Direct substitution refers to the use of other IC without any changes to replace the original IC, the replacement does not affect the machine's main performance and indicators.

The replacement principle is: replace the IC function, performance indicators, package form, pin use, pin number and interval, etc. are the same. Which IC function is the same function not only the same, but also pay attention to the same logic polarity, that is, the output input level polarity, voltage, current amplitude must be the same. Performance indicators refer to the IC's main electrical parameters (or the main characteristic curve), the maximum power dissipation, the maximum operating voltage, frequency range and the signal input, output impedance and other parameters to the original IC similar. Power of small parts to increase the heat sink.

1, the same type of IC replacement

The same type of IC replacement is generally reliable, the installation of integrated PCB circuit, we should pay attention to the direction of not wrong, otherwise, when the integrated circuit PCB is likely to be burned. Some single in-line amplifier IC, although the model, function, the same characteristics, but the direction of the order of the pin is different. For example, the two-channel amplifier ICLA4507, the pin has "positive", "anti" points, the starting footnote (color point or pit) in the same direction: no suffix and suffix "R", IC, M5115P and M5115RP.

2, the same type of prefix letters, the number of different IC replacement

This substitution as long as the pin function is exactly the same, the internal PCB circuit and electrical parameters slightly different, but also directly replace each other. Such as: sound put ICLA1363 and LA1365, the latter than the former in the IC 5 feet to increase a regulator diode, the other exactly the same.

Under normal circumstances, the prefix letter is that the manufacturer and the PCB circuit category, prefix letters followed by the same number, most can be directly replaced. But also a few exceptions, although the same number, but the function is completely different. For example, HA1364 is a sound IC, and uPC1364 is color decoding IC; digital is 4558, 8 feet is the op amp NJM4558, 14 feet is CD4558 digital PCB circuit; so the two can not replace. So it must also look at the pin function.

Some manufacturers introduce unencapsulated IC chips, and then processed into products named by the factory, as well as to improve the performance of certain parameters to improve the product. These products are often named with different models or with the model suffix to distinguish. For example, AN380 and uPC1380 can be directly replaced, AN5620, TEA5620, DG5620, etc. can be directly replaced.

Second, non-direct substitution

Non-direct substitution means that ICs that can not be directly replaced can modify the peripheral PCB circuit, change the arrangement of the original pin or increase or decrease the individual components, etc., making it a replaceable IC method.

Substitution principle: Replace the IC with the original IC pin function is different from the shape of different, but the function should be the same, the characteristics should be similar; replacement should not affect the original performance.

1, different packaging IC replacement

The same type of IC chip, but the package shape is different, as long as the replacement of the new device pins as the original device pin shape and arrangement of plastic. For example, AFTPCB circuit CA3064 and CA3064E, the former is a circular package, radial pin: the latter is a dual in-line plastic package, both internal features exactly the same, according to the pin function can be connected. Double row ICAN7114, AN7115 and LA4100, LA4102 package form is basically the same, the pin and the heat sink is a difference of 180 degrees. The front of the AN5620 with heat sink dual inline 16-pin package, TEA5620 dual inlaid 18-pin package, 9,10 feet in the integrated PCB circuit on the right, the equivalent of AN5620 heat sink, the other other feet arranged the same, Will be 9,10 feet connected to the ground can be used.

2, PCB circuit function is the same but the individual pin function of different lC replacement

Substitution can be based on the specific parameters of each model IC and instructions. Such as the TV in the AGC, video signal output is positive and negative polarity difference, as long as the output side of the adapter can be replaced after the adapter.

3, the same type of plastic pin function of different IC replacement

This replacement needs to change the peripheral PCB circuit and pin arrangement, which requires a certain theoretical knowledge, complete information and rich practical experience and skills.

4, some empty feet should not be grounded

Internal equivalent PCB circuit and application of some of the PCB circuit leads to the pin is not marked, encountered empty lead pin, should not be grounded, these lead feet for the replacement or spare feet, and sometimes as an internal connection.

5, combined substitution

Combination of replacement is the same type of multi-block IC internal damage to the PCB part of the circuit, re-combined into a complete IC, to replace the bad IC method. Can not buy the original IC case is very applicable. But requires the use of IC internal integrity of the PCB circuit must have an interface lead foot.

The key to non-direct substitution is to find out the basic electrical parameters of the two ICs that are interchangeable, the internal equivalent PCB circuit, the function of each pin, and the connection between IC components. Please pay attention to the actual operation.

(1) integrated PCB circuit pin number order, not wrong;

(2) to adapt to the characteristics of the replacement of the IC, connected with the external PCB circuit components to be a corresponding change;

(3) the power supply voltage and the replacement of the C after the match, if the original PCB circuit power supply voltage is high, should try to buck; voltage is low, depends on whether the replacement IC work;

(4) after the replacement of the IC to measure the static current, such as the current is much greater than the normal value, then the PCB circuit may produce self-excited, then be decoupled, adjusted. If the gain and the original difference, you can adjust the feedback resistance resistance;

(5) after the replacement of the IC input and output impedance to match the original PCB circuit; check its drive capability;

(6) in the change to make full use of the original PCB circuit board on the hole and lead, external wire requirements neat, to avoid the front and rear cross, in order to check and prevent PCB circuit self-excited, especially to prevent high frequency self-excited;

(7) in the power supply before the power supply Vcc circuit is best connected in series with a DC ammeter, buck resistance resistance from large to small observation of integrated PCB circuit changes in the total current is normal.

6, with discrete components replacement IC

It is sometimes possible to replace the damaged parts of the IC with discrete components to restore them. Before replacing the IC should understand the internal functional principle, the normal voltage of each pin, the waveform and the composition of the PCB components with the external working principle. Also consider:

(1) whether the signal can be removed from the workpiece C connected to the external PCB circuit input:

(2) The signal processed by the peripheral PCB circuit can be connected to the next level inside the integrated PCB circuit for reprocessing (signal matching at connection should not affect its main parameters and performance). Such as IC damage IC, from the typical application of PCB circuit and internal PCB circuit, by the sound in the release, frequency and frequency amplification stage into the available signal input method to find the damaged part, if the audio amplification part of the damage, you can use discrete components instead.