How many IC substitution techniques are there in PCB circuit design?
In PCB circuit design, when IC chips need to be replaced, the following is my skills in replacing IC chips, to help designers in PCB circuit design can be more perfect.
First, direct substitution
Direct substitution refers to the direct replacement of the original IC with other IC chips without any changes, without affecting the main performance and indicators of the machine after replacement.
The replacement principle is: the function, performance index, package form, pin use, pin number and interval of the replacement IC are the same. The same function of IC not only means the same function, but also the same logic polarity, that is, the polarity of output and input level, voltage and current amplitude must be the same. The performance index refers to the main electrical parameters (or the main characteristic curve) of the IC, the maximum power dissipation, the highest working voltage, the frequency range and the input and output impedance of each signal should be similar to the original IC. Small power replacement parts to increase the heat sink.
1. Replacement of IC chips of the same model
The replacement of the same type of IC chip is generally reliable, when installing integrated PCB circuit, pay attention to the direction do not make a mistake, otherwise, the integrated PCB circuit is likely to be burned when energized. Some single-row in-line power amplifier IC, although the model, function, characteristics are the same, but the direction of the pin sequence is different. For example, the two-channel power amplifier ICLA4507 has "positive" and "negative" pins, and its starting pin marks (color spots or pits) are in different directions: IC without suffix or suffix "R", such as M5115P and M5115RP.
2. Replacement of different IC models
(1) Substitution of IC with the same type prefix letter and different number. This substitution as long as the pin function between each other is the same, its internal PCB circuit and electrical parameters slightly different, can also be directly replaced with each other. For example: sound put IC LA1363 and LA1365, the latter than the former in the IC fifth foot internal increase a voltage regulator diode, the other exactly the same.
(2) Substitution of IC with different prefix letters and same digits. In general, the prefix letter indicates the manufacturer and the category of PCB circuit. The number after the prefix letter is the same, and most of them can be replaced directly. But there are also numbers, the same number, but the function is completely different. For example, HA1364 is the sound IC, while uPC1364 is the color decoding IC; 455, 8 pin is operational amplifier NJM4558, 14 pin is CD4558 digital PCB circuit; So they can't be substituted at all.
(3) Model prefix letter and number are different IC substitution. Some manufacturers introduce unpackaged IC chips, and then processing into the factory named products. Another example is to improve the product in order to improve certain parameters. These products are often named by type or distinguished by type suffixes. For example, AN380 and uPC1380 can be directly substituted; AN5620, TEA5620, DG5620 and so on can be directly substituted.
Second, indirect substitution
Non-direct substitution refers to the method of slightly modifying the peripheral PCB circuit, changing the original pin arrangement or adding or subtracting individual components of the IC that cannot be directly substituted to make it into a substitutable IC.
Substitution principle: The IC used for substitution can be different from the original IC pin function, shape is different, but the function should be the same, the characteristics should be similar; The replacement should not affect the performance of the original machine.
1. Replacement of IC chips with the same plastic but different pin functions
This kind of substitution needs to change the peripheral PCB circuit and pin arrangement, so it needs some theoretical knowledge, complete data and rich practical experience and skills.
2. PCB circuit has the same function but individual pin functions are different lC chip replacement
The replacement can be carried out according to the specific parameters and instructions of each type of IC. For example, the AGC in the TV, the video signal output has the difference of positive and negative polarity, as long as the output end is connected to the inverter can be replaced. Bioneng belongs to Qinji Group, is the leading electronic industry service platform in China, providing online components, sensor procurement, PCB customization, BOM, material selection and other electronic industry supply chain solutions, one-stop to meet the comprehensive needs of small and medium-sized customers in the electronics industry.
3. Some empty feet should not be grounded without authorization
Internal equivalent PCB circuit and application PCB circuit some of the lead out feet are not marked, encounter empty lead feet, should not be grounded without permission, these lead out feet for replacement or spare feet, sometimes also as internal connection.
4. Substitution of IC chips with different packages
The same type of IC chip, but the package shape is different, as long as the replacement of the new device pin according to the shape and arrangement of the original device pin shaping. For example, AFTPCB circuit CA3064 and CA3064E, the former is circular package, radiate pin: the latter is double in-line plastic package, the internal characteristics of the two are exactly the same, according to the pin function can be connected. Double row ICAN7114, AN7115 and LA4100, LA4102 encapsulation form is basically the same, pin and heat sink exactly 180 degrees. AN5620 with heat sink double-in-line 16-pin package, TEA5620 double-in-line 18-pin package, 9, 10 pin is located on the right side of the integrated PCB circuit, equivalent to the AN5620 heat sink, the other feet of the two are arranged the same, 9, 10 feet connected to ground can be used.