Substitution and detection method of integrated circuit

Substitution of integrated circuits

The interior of an integrated circuit is basically all semiconductors, which concentrates tens of thousands of transistors into a small device. Because of this, there are many integrated circuits that can be replaced with each other. As long as they have the same function and the same working voltage, the voltage of each pin is the same. It is generally used interchangeably (for MCU and memory, internal is also required). The procedure is the same). This feature is very useful for the replacement of some integrated circuits that are not commercially available or overpriced. In addition, the quality of integrated circuits is different from the place of origin, the quality of imported products is the best, the joint venture products are second, and the domestic products are poor, so their prices are also very different. It is not difficult to distinguish domestic integrated circuits. The model prefix is ​​“CD”, which is a domestic product.

Integrated circuit inspection

To check if the integrated circuit is normal, the following methods can be used:

(1) Logic analysis

The so-called logic analysis method means that if it is suspected that there is a problem with an integrated circuit, it can first measure whether the input signal of the integrated circuit is normal, and then measure whether the output signal of the integrated circuit is normal. If there is input without output, it can generally be judged as the integration. The circuit is damaged.

(2) DC resistance comparison method

The DC resistance comparison method compares the DC resistance value of each pin of the integrated circuit to be detected with the DC resistance value of a normal integrated circuit, thereby judging whether the integrated circuit is good or bad. Use the same multimeter and the same electrical blocking position to reduce the measurement error. The DC resistance comparison method can detect integrated circuits of different models and different structures, but must use the same type of normal integrated circuit as a reference.

(3) Exclusion method

The elimination method means that if a certain part of the circuit (including the integrated circuit) is faulty during maintenance, it can be detected whether the discrete components of the circuit are normal. If the discrete component is normal, the integrated circuit has a problem, and the integrated circuit should be considered.

This method does not require the reference material of the integrated circuit, and does not need to understand the working principle inside the circuit. This method is often used in the maintenance of liquid crystal displays.

(4) DC voltage measurement method

The DC voltage measurement method is a common method for detecting integrated circuits, and mainly measures the DC working voltage value of each pin of the integrated circuit to the ground, and then compares with the nominal value to judge whether the integrated circuit is good or bad.