Zhong Xin Tech-Zhong Xin Tech

" < a href =" https://www.diangon.com/wenku/rd/dianzi/ "" > electronic < / a > in the product development and maintenance. Considering the cost, or confirm a < a href = "https://www.diangon.com/wenku/rd/yuanqijian/" "> IC < / a > after damage, often want to find a consistent with the specifications of the original device, model integration block to replace. It is not easy to find a replacement with the original device specification and model, so how to find the replacement of the original integrated circuit devices, has become the key to maintenance. Understand common types of IC faults. Master the principles, methods and precautions of integrated circuit replacement. Can make the repair or replacement of integrated circuit with half the effort. 1, integrated circuit fault type we can make each piece of integrated circuits (hereinafter referred to as "components") as a < a href = "https://www.diangon.com/wenku/rd/dianyuan/" "> < / a > power supply, input, output, and has a certain function of black, It is not necessary to investigate the internal circuit structure, as long as the power supply side and understand its input, output logic relationship is correct, it is considered to be normal, otherwise indicates that the component is faulty. Component faults can be divided into two types: internal circuit faults and external circuit faults. 1. Component internal circuit fault (1) The input and output pins are unsoldered and open. (2) The input and output pins are short-circuited with the Ucc power supply or ground. (3) Short circuit between two leads other than the Ucc power supply and ground wire. (4) Component internal logic function failure 2. Component external circuit fault (1) Short circuit between Ucc power supply and ground cable and external circuit nodes. (2) A short circuit occurs between two nodes other than the Ucc power supply and ground cable. (3) Signal open. (4) the external components failure, such as inductance, < a href = "https://www.diangon.com/wenku/rd/dianrong/" "> capacitor < / a > and resistance, etc. 3. Component static parameter and static function faults To sum up, the failure types of components are no more than open circuit, short circuit and functional failure. A lot of practice has proved that the dynamic parameters (delay time, rising edge time, falling edge time) of the component have less failure, while the static parameters and static functions have more failure. Static parameters and static functions are the parameters and functions tested under dc voltage signals and low frequency signals. Generally, there are 8 kinds of functional faults. (1) The function current of the component is too large and the component is heated, which makes the component function invalid. (2) The input current of the component is too large, so that the load of the front stage is heavier, and the signal or electric flat of the front stage is pulled down. (3) The cross leakage of several input terminals is too large to cause the failure of logic function. (4) There is an open or short circuit in the input and output pins, causing the function to fail. (5) The frequency characteristic of the component deteriorates. When the operating frequency increases, the amplitude of the output level decreases (for example, the component whose operating power voltage is 5V drops to 3V), resulting in functional failure. (6) The load characteristic of the output tube inside the component deteriorates, and the low level increases to be greater than 0.8V (such as between 1V-2V), resulting in logic confusion. (7) The output current of the driver tube inside the component is too small. Cannot drive the next level load. Error logic. (8) The high and low levels do not meet the requirements, such as the low level is greater than 0.6V, the high level is less than 2.8V, such a level is generally called dangerous level or unreliable level. Components with such output levels should be removed. It is important to note that when the output of the collector open gate assembly is not matched with a resistor, the fault level can also be generated, but this is not a fault of the assembly. Should not be removed. The above fault types belong to digital integrated circuits. For other integrated circuits (such as analog circuit integrated circuit) can be used as a reference. 1. The outline specifications and lead sequence should be the same. Try to choose the same type of integrated circuit or other models that can be directly replaced. This can be done without changing the design or the lead of the original circuit. Simple and easy to meet the design requirements or restore the original performance index. There are a few integrated circuits, although the model is the same, but the overall size has to be considered. 2. The circuit structure and process type should be the same, such as TTL to TTL, CMOS to CMOS, ECL to ECL, etc. 3. The functional characteristics of the circuit should be the same. Make sure that the replacement integrated circuit is good. 4. Some of the main parameters of the circuit should be the same or similar, such as the power supply voltage, working frequency, etc. First, you should be familiar with the naming methods of integrated circuits at home and abroad, and refer to the relevant integrated circuit data replacement manual. And then decide which model to choose as a replacement. 1. The models have different letters but same numbers. For example, CD4001, TC4001, SCL4001, HCF4001, CC4001 and so on are all the same functional products, and the pin arrangement is exactly the same, and the basic principle of station replacement. In general, this is a direct substitution. Satisfactory replacement results are usually obtained, but there are exceptions where further reference to relevant information is required for confirmation when complete confidence is not achieved. 2. The model letters are the same, but numbers are different. This kind of case is the same manufacturer different series or improved product commonly, the possibility that replaces is very big. 3. Different models and letters. In this case, there are many models that can be replaced, mainly because the manufacturers copy each other, as long as the replacement table of the relevant data manual can be found. 4. Different number of pins. This may seem unlikely, but it is possible. Because the function is the same and the pins are different, the pins are generally added to the cooling foot or the common foot. 5. Different encapsulation. This happens more often than not. As a function of the product has a metal round packaging and double - in - line packaging. The packaging is different, but the electrical characteristics are exactly the same. By lengthening the pins and covering the insulation sleeve, and connecting according to the pins' functional requirements, the replacement can be completed. Of course, only when there is really no alternative. 1. The integrated circuit of the same model can be replaced directly. 2. Do not be impatient when replacing the IC on the original machine. Also do not pull, pry the pins of the integrated circuit. According to their own conditions to choose the disassembly method. 3. It has not been determined whether the peripheral circuit is faulty. And before the confirmation of the damage of the integrated circuit, do not easily replace the integrated block, otherwise the integrated block may be scrapped again. 4. Some integrated circuits, although most of the characters in the model are the same but their suffixes are different, the pin arrangement may be different, such as M5115 and M5115R, the two pin function of the order is opposite. 5. When selecting the same function but different models or different pin arrangements, attention should also be paid to: (1) as far as possible choose function, < a href = "https://www.diangon.com/diangong-112-1.html" > electric < / a > the same or similar features of manifold blocks. (2) When the pins are connected, the holes and lines on the original printing plate should be used as far as possible. The lines should be neat, and the number of signals before and after should not cross, so as to avoid the circuit interference, short circuit and other faults. (3) The supply voltage of the integrated circuit should be consistent with the typical ＆#118alue of the supply voltage of the integrated circuit. (4) the input and output impedance of each signal of the integrated circuit should match with the original circuit.