The Researches On Mixed-Signal Test And Design For Testability

With the rapid development of IC design and manufacturing technology, the complication of IC is increasing with its size decreasing, and the test of VLSI is becoming a more and more difficult problem. Specially, when entering the deep sub-micron processing technique and ultra high integrated period, vary IP cores are integrated, and the function of SOC is becoming more and more powerful, but it also brings out a series of design and testing problems. The theory and technology of testing and testable design have become an important research direction in VLSI field, and it is much more valuable in theory and practice.This paper starts with the basic testing theory and method, and then gets a more deep research into the testability of system level mixed-signal chip. First, analysis of the system level chip testability is started from the basic fault model, and a primary analysis is made on fault classification, fault simulation, test generation and algorithm. Then a deeper research is made on testability of design, including scan test, boundary scan test, build in self test and IDDQ test. An example is also proposed to demonstrate BIST based on FPGA, including modules of test pattern generator, kernel circuit under test and feature analyzer. To demonstrate the correctness and efficiency of BIST, a fault is injected into a normal circuit, and then a simulation is performed on both the normal circuit and the circuit with fault injection. A special discussion on testing the mixed signal circuit is performed, and a comparison is carried out on the simulation strategy between analog circuit and mixed signal circuit to illustrate the difficulty in designing and simulating the mixed-signal circuit. Also, an introduction to the VHDL-AMS language is made, which is used to describe mixed signal design and its simulation, and the paper is also pointed out the basic design flow using VHDL-AMS and the extended new concept of VHDL-AMS. The application of 1149.4 standard of mixed signal test bus in VLSI is also introduced. Last, the paper introduces the mixed signal test theory based on DSP, and a detailed scheme of testing DAC based on DSP is offered. The paper also presents the hardware and software design of the auto test equipment based on DSP which can be used to test integrated circuit and PCB board.In conclusion, the design method of testability for mixed-signal chip with lower cost, higher fault coverage and higher reliability is the demand of further development of system level chip.