Voltage diagnosis appeared earlier and is widely used

Voltage diagnosis appeared earlier and is widely used. The observation information of voltage testing is the logical output value of the tested circuit. This method obtains the corresponding logic output value of the circuit by inputting different test vectors into the circuit, and then compares the collected circuit logic output value with the expected logic output value of the circuit corresponding to the input vector, in order to achieve the goal of detecting whether the circuit can achieve the expected logic function in the actual operating environment. This method is simple but not suitable for large-scale integrated circuits with high redundancy. If the defect appears in the redundant part, it cannot be detected. Moreover, when the circuit scale is large, the set of test vectors will also grow exponentially, which directly leads to difficulties in generating test vectors and low diagnostic efficiency. In addition, voltage diagnosis cannot detect faults that only affect circuit performance rather than circuit logic functionality. Due to the fact that the voltage logic value output by integrated circuits may not necessarily be related to all nodes in the circuit, voltage testing cannot detect non functional failure faults in integrated circuits. So, in the early 1980s, diagnostic techniques based on integrated circuit power supply currents were proposed. The power current is usually directly or indirectly related to all nodes in the circuit, so current based diagnostic methods can cover more circuit faults. However, the introduction of current diagnosis technology is not intended to replace voltage testing, but to supplement it in order to improve the detection rate and coverage of fault diagnosis. Current diagnosis technology can be divided into static current diagnosis and dynamic current diagnosis. The core of static current diagnosis technology is to compare the power supply current of the tested circuit in a stable operating state with a pre-set threshold to determine whether there is a fault in the tested circuit. It can be seen that the selection of threshold is the key to determining the detection rate of this method. Early static current diagnosis techniques used fixed thresholds, but fixed thresholds were not suitable for the development of integrated circuit chips towards deep submicron technology. So, later generations continuously improved the static current detection method, and successively proposed differential static current detection technology, current ratio diagnosis method, static current detection technology based on clustering technology, etc. Dynamic current diagnosis technology was introduced in the 1990s. Dynamic current can directly reflect the frequency of internal voltage switching in a circuit during state transition. The detection technology based on dynamic current can detect faults that cannot be detected by the previous two methods, further expanding the fault coverage range. With the development and gradual maturity of intelligent technology, integrated circuit chip fault detection technology is also moving towards the trend of intelligence