IBIS Introduction
IBIS (I/O Buffer Information Specification) provides a standard way to model the electrical specifications of common digital electrical devices. This allows a PCB designer to verify and refine a PCB (Printed Circuit Board) design using simulation tools built into modern PCB design tools. In many respects, the IBIS models complement the SPICE behavior models providing enhanced simulation capabilities for the designer.
The primary purpose of IBIS is to provide freely available models for digital semiconductors without necessarily revealing the proprietary nature of a product. Rather than providing a SPICE model with specific NMOS configurations, IBIS provides a model describing the time-dependent voltage and current for an I/O pin.
Quick link: to find an IBIS model for a particular component, please follow this link.
IBIS Components
IBIS consists of three general parts:
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The real-world components.
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The files characterizing the I/O characteristics of the real-world components.
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PCB design and simulation software that can interpret the model and provide meaningful feedback to the designer. For example, a designer may be able to observe the virtual signal on a PCB.
Tech Tip: There is a truism in the statement that all models are wrong. The suitability of any individual model is dependent on the performance of the design. As a new digital designer, you were likely content to construct a simple AND logic or a state machine. As your understanding grows, the early models are insufficient for your high-speed design as there are so many additional elements to consider. This is where IBIS can help identify the steps necessary to maintain signal integrity.
To learn more about IBIS please review the material provided by:
Best Wishes,
APDahlen
About the author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.