Analysis And Research Of Signal Integrity In The Design Of High Speed Digital Circuit

With the development of the microelectronics technology and computer science, they have become more and more the designs of high speed digital systems and the use of high speed devices. In this kind of design, because of quickly raised systematic clock frequency, continuously shorten signal jump edge, and increased integrated degree of circuit, the line's mutual link of printed circuit board and board layer's property have influenced more and more greatly the systematic electrical performance.For the design of low frequency circuit, the mutual link relations can be regard as lumped parameters, and the influence of line's mutual link and board layer's property can be neglected. In the design of high speed digital circuit, a segment of the conductor not only is a conductor, but also becomes a transmission line with distributed parameters. The mutual link relations must be considered as transmission line, and the electric parameter of the printed circuit board is also considered. Therefore, the design of high speed digital circuit must face the signal integrity problems, such as reflection, crosstalk, overshoot, oscillation and simultaneous switching noise, all of which are caused by the postponement of mutual link.Signal integrity's problems may cause or directly bring about signal distortion, wrongly timing, incorrect data, as well as working wrongly of the system, and even system's collapse. Improper solutions may affect seriously product's performance, and even bring immeasurable loss. Therefore, for the high speed system, the signal integrity must be taken into consideration and simulation analyses be conducted in the process of circuit design.It is an important method of solving signal integrity problems to build model and carry out simulation of circuit in reasonable way. By simulating analysis, the hidden problems of signal integrity can be discovered to the greatest extent before PCB being made, and the probability of the failure that is caused by signal integrity problems is reduced at the lowest lever in designing products, then it can be possible that products be developed only one time and succeed, so the development period is shorten and the cost is reduced.The signal integrity in the design of high speed digital circuit is analysed andresearched in detail in this paper. The main contents include: to introduce the fundamental theories of signal integrity's analysis and research in the design of high speed digital circuit, including high speed circuit theory, electromagnetic field theory and transmission line theory; to analyze the reasons of reflection, crosstalk and the simultaneous switching noise in theory; in practice, by IBIS model, to simulate the reflection and crosstalk of the circuit model using the Hyperlynx simulation software of Mentor company, and to show the waveforms of reducing reflection by using termination technique and the waveforms of the crosstalk's influence with changing the distance of transmission lines and the length of transmission lines. It summarized the solutions to reflection, crosstalk and the simultaneous switching noise, and discussed the strategy of signal integrity simulating analysis in the design of high speed digital circuit.