In the PCB circuit design will meet the need to replace the IC chip, the following will say that I replace the IC chip skills, to help designers in the PCB circuit design can be more perfect.

First, direct substitution

Direct replacement is to use other IC chip without any changes and directly replace the original IC, replacement does not affect the main performance and indicators of the machine.

The replacement principle is: the replacement IC function, performance index, package form, pin use, pin number and interval and other aspects are the same. The same IC function not only refers to the same function, but also should pay attention to the same logic polarity, that is, the output input level polarity, voltage, current amplitude must be the same. Performance index refers to the IC main electrical parameters (or the main characteristic curve), the maximum dissipated power, the highest operating voltage, frequency range and the signal input, output impedance and other parameters to be close to the original IC. Low power substitute to increase the heat sink.

1, the same type of IC chip replacement

The same type of IC chip replacement is generally reliable, the installation of integrated PCB circuit, should pay attention to the direction of not mistaken, otherwise, power when the integrated PCB circuit is likely to be burned. Some single in-line power amplifier IC, although the model, function, characteristics are the same, but the direction of the pin arrangement order is different. For example, dual channel power amplifier ICLA4507, the pin has "positive", "negative" points, its starting pin annotation (color points or pits) direction is different: no suffix and suffix for "R", IC, such as M5115P and M5115RP.

2. Replacement of different types of IC

(1) Replacement of IC with the same prefix letters and different numbers. As long as the pin function of each other is exactly the same, its internal PCB circuit and electrical parameters are slightly different, it can also be directly substituted with each other. Such as: the accompanying sound put IC LA1363 and LA1365, the latter than the former in the IC fifth foot internal increased a voltage regulator diode, other exactly the same.

(2) Model prefix letters are different, the same number of IC substitution. In general, prefix letters indicate manufacturers and PCB circuit types. The numbers after prefix letters are the same, and most of them can be directly substituted. But also count, although the number is the same, but the function is completely different. For example, HA1364 is a sound IC, while uPC1364 is a color decoding IC; 4558-pin is operational amplifier NJM4558, 14-pin is CD4558 digital PCB circuit; So they're not interchangeable at all.

(3) Model prefix letters and numbers are different IC substitution. Some manufacturers introduce IC chips without packaging, and then processed into products named by our factory. Another example is to improve the product in order to improve certain parameters and indicators. These products are often named by different models or distinguished by model suffixes. For example, AN380 and uPC1380 can be directly substituted; AN5620, TEA5620, DG5620 can be directly substituted.

Second, indirect substitution

Non-direct substitution refers to the IC that can not be directly substituted to slightly modify the PCB circuit, change the arrangement of the original pin or add or subtract individual components, so that it becomes a substitutable IC method.

Substitution principle: the IC used for substitution can be different from the original IC pin function, different shape, but the function should be the same, the characteristics should be similar; The performance of the original machine should not be affected after the replacement.

1, the same as plastic but the pin function of different IC chip replacement

This kind of substitution needs to change the PCB circuit and pin arrangement, so it needs certain theoretical knowledge, complete data and rich practical experience and skills.

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

The replacement can be carried out according to the specific parameters and instructions of each type IC. For example, the AGC and video signal output in the television set have the difference of positive and negative polarity, so long as the output end of the inverter can be replaced.

3, some empty feet should not be grounded without authorization

Internal equivalent PCB circuit and application PCB circuit some lead feet are not marked, when encountering empty lead feet, should not be grounded without authorization, these lead feet are replacement or spare feet, sometimes also as internal connection.

4, different packaging IC chip substitution

The same type of IC chip, but the package shape is different, as long as the pin of the new device according to the shape and arrangement of the original device pin shaping. For example, AFTPCB circuit CA3064 and CA3064E, the former is circular package with radial pin, while the latter is double in-line plastic package. The internal characteristics of the two are exactly the same, and can be connected according to the pin function. Double row ICAN7114, AN7115 and LA4100, LA4102 packaging form is basically the same, pin and heat sink are exactly 180 degrees difference. The aforementioned AN5620 with heat sink dual-row in-line 16-pin package and TEA5620 dual-row in-line 18-pin package, pins 9 and 10 are located on the right side of the integrated PCB circuit, equivalent to the heat sink of AN5620. The other pins of the two are arranged in the same way, and pins 9 and 10 can be used by connecting them to ground.