I <sub> Of Ddt </ Sub> Dynamic Current Test Methods,

Testing of digital circuits is an important part of the production of ICs. The research about the testing of digital circuits is of great practical value for the quality of 1C products.Traditional testing methods based on voltage testing have been widely used in practice. But there are still some defects in circuits that can not be detected by those traditional testing methods. As an enhancement of these methods, current testing can increase the fault coverage and make higher the reliability of ICs. The dynamic power supply current (IDDT) is a new window through which we can observe the switching activities in digital circuits. IDDT testing methods make possible further increasing the fault coverage.By exploring the characters of dynamic power supply currents of digital circuits using SPICE, this paper analyzed the relation between IDDT and the switching activities when a circuit changes from one logical state to another. Based on experimental results, this paper came up with a method to estimate the average dynamic power supply current by counting the weighting logical transitions in the circuit. In this way, a simple and direct relation was build up between logical transitions and dynamic current, which makes possible IDDT testing pattern generation on logical level.This paper made some improvement on a Boolean process based IDDT testing method, and implemented it using a waveform simulator. For some faults in a circuit, testing pairs was generated using this method. SPICE experiments were done to simulate the dynamic currents of both the fault circuits and fault free circuits under the function of testing pairs. The simulation results showed that there are some differences between the waveforms of currents. By comparing the average dynamic currents, these test pairs can detect some faults. All these proved the validation and feasibility of this IDDT testing method based on Boolean process theory.