Harmonizing Circuit Design and EMC DesignPart 11 Websites (2) Application Notes and Design Models

Hello! I’m Inagaki, at ROHM.

This 11th column is our second on websites. Systematically organizing the information obtained from ROHM’s website, we obtain something like the following.

• ・Websites can be used to learn about current events.
• ・Websites can be used to study.
• ・Websites can be used to obtain product information.
• ・Websites can be used to obtain calculation models.
• ・Calculations can be performed on websites.
• ・Products can be purchased from websites.
• ・Questions can be asked from websites.

One is not limited to mere collection of information; it is possible to actively utilize websites–learning, calculating, asking questions.

Let’s have a look at “Application Notes and Design Models“, accessed by selecting “Design Support” in the “Technical Support” menu item on the top page.

This corresponds to “obtain product information” and “obtain calculation models” in the above list. Specifically, the following structure is used. As the Document Type, the page is divided into five categories: 1. Technical Document, 2. Design Model, 3. 3D Data, 4. Symbol/Footprint, and 5. Simulation (circuit simulations); relevant documents are made available by category. Upon clicking on a document name in the index, a list of the relevant documents appears in a table. Moreover, a search function is provided, so a particular product name or a document to which a keyword applies can be found as well.

Among these documents, the SPICE* models and the IBIS models in the second of the above, Design Models, may be the resources that people are most likely to use of late.

SPICE models are files of numerical values (in a text format) used to obtain equivalent electrical characteristics by analyzing (simulating) a circuit on a computer, without even the need to perform measurements of an actual LSI. The overall operations of a SPICE simulation are the circuit analyses that can be performed by a SPICE simulator (representative commercial products include PspiceR and LTspiceR), which can be broadly categorized as direct current (DC) analyses, alternating current (AC) analyses, and transient (TRAN) analyses. In a SPICE simulator, the physical characteristics (electrical characteristics) of transistors and diodes are numerically approximated, and the formulas for these approximations are incorporated within (and cannot be changed by users). A SPICE model collects only the coefficients of these formulas, and by changing the numerical values of the coefficients, various transistors and diodes can be represented (values can be changed by users).

The formulas and formats incorporated into SPICE simulators differ slightly depending on the commercial product, and so the corresponding SPICE models also differ with the product. That, is, SPICE models also have something akin to “dialects”. For example, the SPICE models used with PspiceR and the SPICE models for use with LTspiceR are different in this way. Incidentally, SPICE simulators and SPICE models were developed by students at the University of California at Berkeley in 1973, and these are the ancestors of today’s commercial products.

*SPICE (Simulation Program with Integrated Circuit Emphasis)

Moreover, at a “Spice Community” website, there are over 5,000 SPICE models for such ROHM products as LSIs (integrated circuits), transistors, and diodes (individual semiconductors), which can easily be downloaded. They can be accessed from the following URL.

https://www.pspice.com/models/rohm

Thank you very much for your attention.