High accurate SPICE models that can more accurately simulate the transient characteristics of power devices
Environments surrounding SPICE models for discrete power devices
In recent years, information and telecommunications equipment and industrial equipment not only require high-value-added products with enhanced functionality, miniaturization and weight reduction, but also require environmentally conscious products with energy saving. Performance of electric circuits and power devices installed in circuits is greatly related to reducing the power consumption of these devices. Conventionally, in designing electric circuits, components are actually mounted on circuit boards to evaluate circuit characteristics such as power conversion efficiency and response speed of voltage or current during switching. However, if similar evaluations can be realized with high accuracy and in a short time by circuit simulation, development efficiency will be improved by reducing the number of prototypes of boards and shortening the development period, thereby contributing to higher performance of equipment. From this background, circuit simulators are also being actively used in electrical circuit design.
On the other hand, in the power electronics and automotive fields such as automobiles, there is a strong demand for preliminary predictions based on circuit simulations of the noise emitted from the entire system and the power dissipation of the entire system. Therefore, there is a growing demand for SPICE model for power semiconductors that can predict power conversion efficiencies, EMI (Electro-Magnetic interference) noises, and other factors of the circuitry installed in the system with high accuracy. Toshiba Device & Storage Co., Ltd. has been promoting the development of SPICE models compatible with discrete power devices. In addition to SPICE model (G0 model) which emphasizes computational speed rather than accuracy, we have also begun providing a high accurate SPICE model (G2 model) which can reproduce transient characteristics more accurately.
Type of SPICE model
In modeling the behavior of semiconductor elements used in circuit design, there are multiple types of representation methods.
| Mathematical model | Table look-up model | Compact model | Macro model | |
|---|---|---|---|---|
| Features of the model | Model that is formulated using fitting functions for all electrical characteristics of the device. | Model that create a database of the tables created for target numeric data such as measured values. | Modeling method for semiconductor devices with generalized device structures, such as MOSFET and BJTs, based on the physical formula of semiconductors. | Model that combines multiple compact models to match the structure of the target element. |
| Advantage | High accrate SPICE model can be made by using appropriate mathematical formulas. | It is possible to make a very high accurate model, because the measured data is made into a database as it is. | Because it is built into the circuit simulator of each EDA vendor, the user can select an appropriate model from the compact model built into the circuit simulator and proceed with the circuit design work. | Even with a new device structure, it is easy to develop and create a model that follows a relative device structure. |
| Disadvantage | The mathematical formula used to increase the reproduction accuracy tends to be complicated, and as a result, convergence and calculation speed may get lowered. | In order to predict unintentional behavior during switching, it is necessary to obtain data at all operating points at sufficiently fine intervals, so a very large number of man-hours are required for preparing a SPICE model beforehand. | Since the developer of each compact model is limited to nonprofit organizations such as universities and research institutes, etc., and there are restrictions on development, so the reproduction accuracy of electrical characteristics may get lowered in the element structure which is not assumed. | The number of nodes of the whole circuit tends to increase by complicating the model configuration in order to improve the reproducibility of electrical characteristics, and as a result, the convergence and calculation speed of the circuit simulation may get reduced. |
※SPICE: Simulation Program with Integrated Circuit Emphasis
※MOSFET: Metal Oxide Semiconductor Field Effect Transistor
※BJT: Bipolar Junction Transistor
※EDA: Electronic Design Automation
Features of TOSHIBA CORPORATION's high accurate SPICE model (G2 model)
Toshiba’s high accurate SPICE model (G2 model) for discrete power device is created by macro model format, so G2 model can represent the electrical characteristics with a few non-linear element and a continuous arbitrary function. As a result, it has advantage of limiting the demerits of macromodel as much as possible, which are degradation in circuit simulation convergence and calculation speed due to increase in number of nodes. While the G0 model which has a faster calculation speed and is suit for function checking, the G1 and G2 model enable high accurate switching simulations that are closer to actual measurements by improving the voltage-dependent characteristics of the parasitic capacitance. Furthermore, the G2 model improves the reproducibility of the high-current-domain characteristics of ID-VDS curve.
| SPICE Model grades | ID-VDS | Crss-VDS | Coss-VDS | Ciss-VDS |
|---|---|---|---|---|
| G0 (RMS error criterion) |
○ (15％ or less) |
× (Not applicable) |
× (Not applicable) |
○ (Not applicable) |
| G1 (RMS error criterion) |
○ (15％ or less) |
○ (2％ or less) |
○ (2％ or less) |
○ (2％ or less) |
| G2 (RMS error criterion) |
○ (5％ or less) |
○ (2％ or less) |
○ (2％ or less) |
○ (2％ or less) |
※RMS error: The RMS error used as the basis for modeling (Root Mean Square: square root). RMS errors do not guarantee simulation errors.
※For more information on the grades of our SPICE models, please refer to the application note.