Quartus® Prime Pro Edition User Guide: PCB Design Tools

ID 683768
Date 4/01/2024
Document Table of Contents

1.2. I/O Model Selection: IBIS or HSPICE

The Quartus® Prime software can export two different types of I/O models that are useful for different simulation situations, IBIS models and HSPICE models.

IBIS models define the behavior of input or output buffers through voltage-current (V-I) and voltage-time (V-t) data tables. HSPICE models, or decks, include complete physical descriptions of the transistors and parasitic capacitances that make up an I/O buffer along with all the parameter settings that you require to run a simulation.

The Quartus® Prime software generates HSPICE decks, and adds preconfigured I/O standard, voltage, and pin loading settings for each pin in your design.

The choice of I/O model type is based on many factors.

Table 1.  IBIS and HSPICE Model Comparison
Feature IBIS Model HSPICE Model
I/O Buffer Description Behavioral—I/O buffers are described by voltage-current and voltage-time tables in typical, minimum, and maximum supply voltage cases. Physical—I/O buffers and all components in a circuit are described by their physical properties, such as transistor characteristics and parasitic capacitances, as well as their connections to one another.
Model Customization Simple and limited—The model completely describes the I/O buffer and does not usually have to be customized. Fully customizable—Unless connected to an arbitrary board description, the description of the board trace model must be customized in the model file. All parameters of the simulation are also adjustable.
Simulation Set Up and Run Time Fast—Simulations run quickly after set up correctly. Slow—Simulations take time to set up and take longer to run and complete.
Simulation Accuracy Good—For most simulations, accuracy is sufficient to make useful adjustments to the FPGA or board design to improve signal integrity. Excellent—Simulations are highly accurate, making HSPICE simulation almost a requirement for any high-speed design where signal integrity and timing margins are tight.
Third-Party Tool Support Excellent—Almost all third-party board simulation tools support IBIS. Good—Most third-party tools that support SPICE support HSPICE. However, Synopsys* HSPICE is required for simulations of Intel’s encrypted HSPICE models.