Particularly today's circuits are working at increasingly high frequencies, such as general digital signal processing (DSP) circuit board application frequency in the 150-200MHz is very common, CPU boards in the actual application of 500MHz or more has been not surprising, in the communications industry in the design of the Ghz circuit has been very popular. All of these PCB board design, often using multilayer board technology to achieve. In the multilayer board design is inevitable for the use of power layer design technology. And in the power layer design, often due to a variety of power supply mixing applications and make the design become very complex. So what are the problems lingering in the PCB engineers? How to define the number of PCB layers? Including the use of how many layers? How to arrange the content of each layer is the most reasonable? Such as there should be several layers of ground, signal layer and ground layer how to alternate arrangements and so on. How to design a multi-category power supply block system? Such as 3.3V, 2.5V, 5V, 12V and so on. Reasonable division of the power supply layer and **** ground is a very important factor in the stability of the PCB. How to design decoupling capacitors? The use of decoupling capacitors to eliminate switching noise is a common means, but how to determine its capacitance? Capacitor placed in what position? When to use what type of capacitors and so on. How to eliminate ground bounce noise? How does ground bounce noise affect and interfere with useful signals? How to eliminate return path noise? In many cases, the circuit design is not reasonable is the key to the circuit does not work, and the circuit design is often the engineers feel the most helpless work. How to rationally design the current distribution? Especially in the ground layer of the current distribution design is very difficult, and the total current in the PCB board if the distribution is not uniform, will directly and obviously affect the PCB board unstable work. In addition there are some common such as upstroke, downstroke, ringing (oscillation), time delay, impedance matching, burr and so on about the signal of the odd problem, but these problems and the above problems are inseparable. They are cause and effect. In general, the design of a good quality high-speed PCB board, should be from the signal integrity (SI - Signal Integrity) and power integrity (PI - Power Integrity) to consider two aspects. Although the more direct results from the signal integrity of the performance, but the cause, we must not ignore the power integrity of the design. Because power integrity directly affects the signal integrity of the final PCB. There is a very big misunderstanding exists among PCB engineers, especially those who have used traditional EDA tools for high-speed PCB design engineers. There are many engineers have asked us: "Why use EDA tools SI signal integrity tools to analyze the results and we use the actual test results of the instrument is not consistent, and often analyze the results of the more ideal?" This is a very simple question. The cause of this problem is: on the one hand, the EDA vendor's technical staff did not explain clearly; on the other hand, the PCB designer's understanding of the simulation results of the problem. We know that the current Chinese market to use more EDA tools are mainly SI (signal integrity) analysis tools, SI is not to take into account the impact of the power supply based on wiring and device models and analysis, and most of the analog devices are not even taken into account (assumed to be ideal), it can be imagined that the results of such an analysis and the actual results are certainly inaccurate. Because in most cases, the PCB board in the power integrity of the impact than the SI is more serious. At present, although some EDA vendors have been part of the provision of PI (Power Integrity) analysis function, but because of their analysis function and SI (Signal Integrity) is completely separate, the user still has no way to see and the actual test results are close to the analysis report. PI and SI are closely related, and in many cases, the main cause of signal variance is the power supply system. For example, decoupling capacitors are not well designed, the ground layer design is not reasonable, the impact of the loop is very serious, the current distribution is not uniform, the ground bomb noise is too large and so on. As PCB design engineers, in fact, very much hope to see close to the actual results of the analysis report, so that it is easy to correct and troubleshooting, to achieve the true meaning of the simulation of the design of the effect of the emergence of SPI tools to make the above discussion possible. SPI's acronym is Signal-Power Integrity, as the name implies, it is the SI signal integrity and PI As the name suggests, it is an analysis tool that integrates SI signal integrity and PI power integrity into one. SI and PI are no longer isolated from each other. APSIM-SPI is the first and only product in the industry that combines signal integrity and power integrity. With the SPI tool, PCB engineers can observe the waveforms from the simulation in a more realistic way, which is very close to the actual test with the instrument. In other words, from now on, the theoretical design and the actual test will be comparable. Previously, the SI function was an isolated analysis under the assumption that the power supply layer was ideal. Although this is a great help, it does not have an overall effect, and it is difficult for the user to rule out errors simply based on the results of the SI analysis. To make an assumption, if a PCB board, because of its VCC and GROUND line is very thin, the circuit does not work naturally at this time. With an oscilloscope and other instruments, it is also easy to find that the signal is very serious. However, for this kind of easily imaginable design, if you use the general SI analysis tool, it is impossible to simulate the odd variation of the signal. At this time, although the simulation results of the waveform is very complete, there is no odd change, but in reality, it has been odd to the point of not working. So some engineers have questioned: "Why when we will be the PCB board in the power and ground lines no matter how narrow, SI simulation of the signal waveforms have not changed? , the reason is that the SI simulation does not take into account your PI, that is to say, does not take into account your power lines and ground lines. To solve this problem, the only way is to use the SPI tool, SPI in the SI signal integrity analysis is to fully consider the ground layer, including the signal layer of the ground wire, as well as a large area of the ground signal padding and so on. The unstable signals or disturbances in the ground layer will be completely superimposed on the SI simulation results. This can simulate the real actual working effect, of course, the final result is close to the actual test results. It is easy for engineers to consider and correct intuitively. APSIM-SPI in order to realize the organic combination of SI and PI, whether from the internal model, calculation methods, user interface, analysis functions and simulation mechanism have made significant adjustments. The purpose is to ensure the perfection of the SPI function while making it easy for users to use. For example, in the RLGC modeling and distribution parameter extraction, the RLGC parameter extraction in SPI is much more complicated than the simple SI parameter extraction in the past. It is because the parasitic parameters of the ground layer and the connection relationship between the ground layer and the signal line must be fully considered in SPI. APSIM-SPI will fully consider the effect of the ground layer in the signal singularity analysis. Because SPI will model the parasitic parameters of the ground layer together with the parametric model of the signal wiring, and the IBIS or SPICE model of the device, the effect of the ground layer will be fully considered. Therefore, no matter the decoupling capacitors, filter capacitors, terminal resistors and other analog components in your design, or the SSO switching noise, ground bounce noise, etc. generated by the circuit in operation, they will all be reacted together in the final simulation results waveforms. The use of APSIM SPI tools, PCB engineers in the design of PCB boards can intuitively observe the signal of the odd change in the situation, and make timely adjustments. Such as when they found their own ground cloth is not wide enough, the signal will have noise, or even deformation, then you can adjust the width of the ground until satisfied to. How wide should the ground wire be in the past? Engineers can only rely on experience to debug, there is no tool to assist them in design guidance. And if the ground is not good, the probability of causing the PCB board does not work will be very large. But today's PCB board is so complex, not only the width of the ground, but also should include the ground plane filling, multi-layer ground plane design, especially the ground plane of the split technology processing, etc., for different frequencies to use different processing methods. If the limited experience alone is certainly not able to meet the design requirements. Now with the help of APSIM-SPI, PCB engineers can easily know his ground plane, ground system design is reasonable and effective. For example: when designing multilayer boards, many engineers have to consider how to arrange each layer often do not know whether to put the first signal layer or the first ground layer? Is the signal layer and ground layer alternately or centrally placed? Now engineers can be based on SPI simulation results, clearly get which method is the best results. Another example: when there are multiple power supplies on the ground layer, such as 3.3V ground, 2.5V ground, 5V ground, etc., how to divide the processing? In the past, engineers could only rely on limited experience, and could only consider the reasonableness from the boundary division. If this aspect of the design is not reasonable, the consequences are imaginable, I believe that engineers have a very deep experience. But because the ground layer is often in the middle of the PCB board, because the physical contact is not at all, debugging is very difficult to modify. In fact, in the multi-power ground layer design, not only to consider the boundary between the various territories, but also consider the filtering problem, **** ground problems and so on. With the SPI tool, engineers can easily carry out the rational design of multi-power geographic division. If it is not reasonable, then the signal will be distorted during simulation, which was not possible before. In dealing with ground bounce noise and SSO switching noise, we know the seriousness of this noise (in EDA, this noise is summarized in the scope of the PI power integrity analysis), especially high-speed PCB, often encountered unstable operating conditions, in fact, it is likely to be due to switching noise or ground bounce noise caused. Engineers must also know some simple ways to deal with. But from a quantitative point of view, it is very complex. For example: a simple effective way to eliminate SSO switching noise in the power supply and ground between the addition of filter capacitors, commonly used method is to add a number of different quality and type of electrolytic capacitors, engineers must be very easy to quantitatively determine the maximum voltage of these capacitors, (as long as the operating voltage according to the PCB board can be calculated), but how to quantitatively determine the capacitance of these capacitors (capacitance value) is often only based on Experience, or reference to other circuit design. Because to * theory to calculate will be very difficult. Especially now that the PCB circuit is so complex it is not easy to * manual calculation. Capacitor placement is also not easy to determine one of the factors. But the placement of these electrolytic capacitors and its filtering effect will be closely related. (A common method is to place them at the power inlet of the PCB). Now using the APSIM-SPI tool, engineers can easily design and verify the effect of these filter capacitors. And effectively determine the placement of these capacitors and their capacitance values. Extra capacitance is determined not to have, should have the capacitance must not be missing! APSIM-SPI also has many other features related to signal singularity and simulation design. We believe that the current high-speed PCB design must be carried out using advanced means of assistance, SPI combined with years of design experience, a collection of advanced SI and PI analysis techniques, direct and realistic simulation of the PCB board's specific operating conditions, closer to the actual test results, SPI provides a new debugging platform, so that years of empirical design methods have been transitioned to a simulation environment. SPI provides a new debugging platform, making the transition from the empirical design method to the simulation environment. Greatly improve the success rate of high-speed PCB design. SPI has gradually become the most popular and essential design and analysis tool for high-speed PCB design engineers, and is used in close collaboration with other PCB design tools in the industry.