Analyzing Your Design Using Circuit Simulation

Now reading version 23. For the latest, read: Analyzing Your Design Using Circuit Simulation for version 24

Mixed-Signal Circuit Simulation

The main purpose of simulating the function of an electronic device is to represent and analyze the performance of the design. It is impossible to imagine the design of even the simplest device without the capabilities that simulation offers. Using simulation software makes it possible to analyze all modes of the device being designed without possible damage, to determine parameters and characteristics that are difficult to measure in real conditions, and to perform measurements that might otherwise require the use of expensive measurement equipment.

SPICE (Simulation Program with Integrated Circuit Emphasis) was developed as an open-source software package, which has led to its broad popularity and continued development. Altium Designer's Mixed Simulation (MixedSim) technology uses an improved core based on SPICE algorithms and is designed to simulate analog, digital or mixed analog-to-digital device electrical circuits. It is a true mixed-signal simulator, meaning that it can analyze circuits that include both analog and digital devices. It is fully SPICE3f5 compatible, as well as providing support for a range of PSpice® and LTSpice® device models.

To learn more about which SPICE models are supported by the simulation engine in Altium Designer, refer to the Supported Spice model Knowledge Base article.
For a quick start with simulation in Altium Designer, you can find a set of simulation examples in the Shared Documents folder (C:\Users\Public\Documents\Altium\AD<Version>\Examples\Simulation Quick Start for default installation). Each example demonstrates a real-world use case of simulation, complete with information on setting up the simulator and interpreting the results.
Altium Designer can import schematics in various formats, including OrCAD®, LTSpice and KiCad®. These are imported using the Import Wizard, with each file type being handled by an extension installed in Altium Designer. Learn more about Interfacing with Other Design Tools.

The simulation process in Altium Designer can be split into the following stages:

  • Verifying & Preparing a Project for Simulation – the design to be simulated should be verified and adequately prepared so you can receive the proper simulation results. This includes placing components with simulations models, setting signal sources and defining points of interest in the circuit using probes. The verification process gives feedback if something is wrong with the schematic to be analyzed.
  • Configuring & Running a Simulation – simulations are performed directly from the schematic and can also be re-run as you analyze the simulation waveforms. Quickly configure the required analysis type and the output expressions to be plotted, then run the simulation.
  • Working with Simulation Results – simulation results are displayed in the SimData editor. This is a feature-rich environment where you can quickly and efficiently analyze simulation results, enabling you to assess, debug and ultimately emerge confident in the operation of your design.

Mixed Simulation – Example Guide

The collapsible section below takes you through the process of creating a simulation-ready schematic of a filter circuit, which is then used to run some circuit simulation analyses.

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The features available depend on your Altium product access level. Compare features included in the various levels of Altium Designer Software Subscription and functionality delivered through applications provided by the Altium 365 platform.

If you don’t see a discussed feature in your software, contact Altium Sales to find out more.