SPICE (Simulation program with integrated circuit emphasis) is the most common circuit-level simulation program. Various software manufacturers provide different versions of spice software such as Vspice, Hspice, and Pspice. spice simulation algorithm.
The designer of the circuit system sometimes needs to make a detailed analysis of the relationship between voltage and current in some circuits in the system. At this time, transistor-level simulation (circuit-level) needs to be done. The circuit models used in this simulation algorithm are the most basic components. And single tube. During the simulation, the I/V relationship of each node is calculated according to the time relationship. This simulation method is the most accurate among all simulation methods, but it is also the most time-consuming.
The components in the analyzed circuit may include resistance, capacitance, inductance, mutual inductance, independent voltage sources, independent current sources, various linear controlled sources, transmission lines, and active semiconductor devices. SPICE has built-in semiconductor device models. Users only need to select the model level and give appropriate parameters.
Spice is a powerful general-purpose analog circuit emulator that has a history of decades. This program is mainly used in circuit analysis programs for integrated circuits. Spice's netlist format has become the usual analog circuit and transistor-level circuit. The first version of the described standard was completed in 1972. It was written in Fortran. It was launched in 1975 as a practical version. In 1988, it was designated as the US National Industrial Standard. It is mainly used for ICs, analog circuits, and digital-analog mixed circuits. , Power circuit design and simulation of electronic systems. Because the Spice simulation program adopts a completely open policy, users can modify it according to their needs, coupled with good practicability and rapid promotion, it has been transplanted to multiple operating system platforms. Since the advent of Spice, its version has been continuously updated. There are multiple versions such as Spice2 and Spice3. The new version mainly enhances circuit input, graphics, data structure and execution efficiency. People generally believe that Spice2G5 is the most successful and effective. Yes, future versions are only partial changes. At the same time, a variety of commercial Spice circuit simulation tools with Berkeley's Spice simulation program as the core are also produced, running on PC and UNIX platforms, many of which are based on the original SPICE 2G6 version of the source code, this is a public publication Version, they have done a lot of practical work on the basis of Spice, the more common Spice simulation software are Hspice, Pspice, Spectre, Tspice,
SmartSpice, IsSpice, etc., although their core algorithms are similar, but the simulation speed, accuracy and convergence are different, among which Hspice of Synopsys and Pspice of Cadence are the most famous. Hspice is the de facto Spice industry standard simulation software. It is the most widely used in the industry. It has the characteristics of high accuracy and powerful simulation functions. However, it does not have a front-end input environment. It needs to prepare netlist files beforehand. It is not suitable for novice users. Main applications For integrated circuit design; Pspice is the best choice for individual users. It has a graphical front-end input environment, user-friendly interface, and high cost performance. It is mainly used in PCB board and system-level design.
SPICE simulation software models and simulators are tightly integrated, so it is very difficult for users to add new model types, but it is easy to add new models, only need to set new parameters for existing model types .
The SPICE model consists of two parts: Model Equations and Model Parameters. Since the model equations are provided, the SPICE model and the algorithm of the simulator can be very closely connected, and better analysis efficiency and analysis results can be obtained.
The SPICE model has been widely used in electronic design. It can perform nonlinear DC analysis, nonlinear transient analysis and linear AC analysis on the circuit. The components in the analyzed circuit may include resistance, capacitance, inductance, mutual inductance, independent voltage sources, independent current sources, various linear controlled sources, transmission lines, and active semiconductor devices. SPICE has built-in semiconductor device models. Users only need to select the model level and give appropriate parameters.
When using the SPICE model to perform SI analysis at the PCB board level, integrated circuit designers and manufacturers are required to provide detailed and accurate descriptions of the SPICE model and manufacturing parameters of semiconductor characteristics of integrated circuit I/O unit subcircuits. Because these materials usually belong to the intellectual property rights and confidentiality of designers and manufacturers, only a few semiconductor manufacturers will provide corresponding SPICE models while providing chip products.
The analysis accuracy of the SPICE model mainly depends on the source of the model parameters, that is, the accuracy of the data, and the applicable range of the model equations. The combination of model equations and various digital simulators may also affect the accuracy of the analysis. In addition, the PCB board-level SPICE model simulation calculation is relatively large, and the analysis is time-consuming.
In order to perform circuit simulation, a model of components must be established first, that is, for various components supported by a circuit simulation program, a corresponding mathematical model must be described in the simulation program, that is, a calculation formula that can be calculated by a computer To express them. An ideal component model should not only accurately reflect the electrical characteristics of components but also be suitable for numerical solution on a computer. Generally speaking, the higher the accuracy of the device model, the more complicated the model itself, and the more the number of model parameters required. In this way, the amount of memory occupied by the calculation increases and the calculation time increases. While integrated circuits often contain a huge number of components, a small increase in the complexity of the device model will double the calculation time. On the contrary, if the model is too rough, it will lead to unreliable analysis results. Therefore, the complexity of the component model used depends on actual needs. If you need to conduct physical model research of components or single tube design, generally use a model with higher accuracy and complexity, or even use a device simulation method that solves the basic equations of semiconductor devices. Two-dimensional quasi-static numerical simulation is a representative of this method. By solving Poisson's equation, current continuity equation and other basic equations combined with precise boundary conditions and geometric and process parameters, the electrical characteristics of the device are fairly accurately given. For general circuit analysis, a simple model (Compact model) that meets certain accuracy requirements should be used whenever possible.
In addition to the device model, the accuracy of circuit simulation also directly depends on the accuracy of the given model parameter values. Therefore, it is hoped that the various parameters in the device model have a clear physical meaning, are directly related to the process design parameters of the device, or can be measured by some test method.
There are two ways to form a device model: one is to start from the electrical working characteristics of the component, treat the component as a'black box', measure the electrical characteristics of its port, and extract the device model without involving the working principle of the device. Called a behavioral model. Representatives of this model are the IBIS model and S-parameters. Its advantages are simple and convenient to model and use, save resources, and a wide range of applications. Especially in the case of high frequency, nonlinearity, and high power, behavior-level models are almost the only choice. The disadvantage is that the accuracy is poor, the consistency cannot be guaranteed, and it is affected by the test technology and accuracy. The other is based on the working principle of components, and based on the mathematical equations of the components, the obtained device model and model parameters are closely related to the physical working principle of the device. The SPICE model is the most widely used of this model. Its advantage is higher accuracy, especially with the development of modeling methods and the advancement and specification of semiconductor technology, people can already provide this model at multiple levels to meet different accuracy needs. The disadvantage is that the model is complicated and the calculation time is long.
SEPIC (single ended primary inductor converter) is a DCDC converter that allows the output voltage to be greater than, less than or equal to the input voltage. The output voltage is controlled by the duty cycle of the master control switch (transistor or MOS tube).
The biggest advantage of this circuit is the same polarity of input and output. Especially suitable for battery-powered applications, allowing the battery voltage to be higher or lower than the required input voltage. For example, the voltage of a lithium battery is 3V ~ 4.2V, if the load requires 3.3V, then the SEPIC circuit can achieve this conversion.
Another benefit is the isolation of input and output, which is achieved by the capacitor C1 on the main loop. At the same time, it has a complete shutdown function. When the switch is closed, the output voltage is 0V.
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