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Solutions Search - LTspice

LTspice IV is a high performance SPICE simulator, schematic capture and waveform viewer with enhancements and models for easing the simulation of switching regulators.  Our enhancements to SPICE have made simulating switching regulators extremely fast compared to normal SPICE simulators, allowing the user to view waveforms for most switching regulators in just a few minutes. Included in this download are LTspice IV, Macro Models for 80% of Linear Technology's switching regulators, over 200 op amp models, as well as resistors, transistors and MOSFET models.

Download LTspice IV

Please send questions or comments to ltspice@linear.com

LTspiceIV: Voltage Controlled Switches

Gabino Alonso - Strategic Marketing Apr 9th 2015
LTspice includes a large number of excellent FET models, but sometimes you need to simulate a simple switch that opens and closes at specific times or under certain conditions.To insert and configure a switch in LTspice… (example is available at \LTspiceIV\examples\Educational\Vswitch.asc) Insert the symbol for the ...

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LTC4226 Parallel MOSFETs in Hot Swap Circuits

Dan Eddleman - Applications Engineer Mar 13th 2015
The Good, the Bad, and the Ugly Introduction While it is often desirable, and sometimes absolutely critical, to use multiple parallel MOSFETs in Hot Swap™ circuits, careful analysis of Safe Operating Area (SOA) is essential. Each additional parallel MOSFET added to a circuit improves the voltage drop, power loss, and ...

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Loop Gain and its Effect on Analog Control Systems

Simon Bramble - Field Applications Engineer Jan 26th 2015
Abstract This article brings together the ideas of open loop gain, closed loop gain, gain and phase margin, minimum gain stability and shows how these parameters are interrelated in a feedback system. It examines loop gain in terms of a theoretical control system as well as practical electronic circuits, including linear regulators. Introduction Bob ...

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LTspice: Connecting the Dots

Gabino Alonso - Strategic Marketing Jan 20th 2015
Sometimes the simplest things elude us. Typically, after placing components in an LTspice schematic you select draw wires (F3), left click to start a wire, left click again to change direction or join, repeat until your circuit is complete and then right click to cancel. But did you know you can draw wires through components ...

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LTspice: Copy and Paste Between Schematics

Gabino Alonso - Strategic Marketing Dec 11th 2014
Sometimes the simplest things elude us. One feature not commonly understood in LTspice is how to copy and paste between schematics using the duplicate command. To copy objects from one schematic to another, in the source schematic, invoke the duplicate command (F6 or Ctrl + C) — the crosshair pointer changes to the duplicate ...

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LTspice: SOAtherm Tutorial

Dan Eddleman - Senior Applications Engineer Oct 8th 2014
Verifying that a Hot Swap design does not exceed the capabilities of a MOSFET is a challenge at high power levels. Fortunately, thermal behavior and SOA may be modeled in circuit simulators such as LTspice IV® . The SOAtherm-NMOS symbol included in LTspice contains a collection of MOSFET thermal models developed by Linear ...

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LTspice: Using an Intrinsic Symbol for a Third-Party Model

Gabino Alonso - Strategic Marketing Sep 9th 2014
LTspice IV can automatically create a symbol for a third-party model, or you can associate a third-party subcircuit with an LTspice intrinsic symbol, as long as the third-party .SUBCKT model and the intrinsic symbol share an identical pin/port netlist order. For example, to add an N-channel MOSFET transistor symbol to a schematic ...

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LTspice: Modeling Safe Operating Area Behavior of N-channel MOSFETs

Dan Eddleman - Senior Applications Engineer Aug 22nd 2014
Introduction Often the most challenging aspect of Hot Swap™ circuit design is verifying that a MOSFET’s Safe Operating Area (SOA) is not exceeded. The SOAtherm tool distributed with LTspice IV® simplifies this task, allowing a circuit designer to immediately evaluate the SOA requirements of an application and ...

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LTspice: Simple Steps for Simulating Transformers

Gabino Alonso - Strategic Marketing Jul 1st 2014
Here is the simple approach to simulate a transformer in LTspice IV: Draft an inductor for each transformer winding Couple them using a single mutual inductance (K) statement via a SPICE directive: K1 L1 L2 L3 1 The last entry in the K statement is the coupling coefficient, which can vary between 0 and 1, where 1 represents ...

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LTspice: Basic Steps in Generating a Bode Plot of SMPS

Gabino Alonso - Strategic Marketing Jun 3rd 2014
Determining the open loop gain from a closed loop switch mode power supply (SMPS) is best solved using Middlebrook’s method, which appears in the International Journal of Electronics, Volume 38, Number 4, 1975. This method injects test signals into the closed loop system to independently solve for the voltage and current ...

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LTspice: Simple Steps to Import Third-Party Models

Gabino Alonso - Strategic Marketing May 3rd 2014
It is possible in LTspice IV to create a new symbol from scratch for a third-party model but who has the time. Follow theses easy steps to generate a new symbol for a third-party model defined in a subcircuit (.SUBCKT statement). Open the netlist file that contains the subcircuit definitions in LTspice (File > Open or ...

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LTspice: SAR ADC Driver Interface

Kris Lokere - Signal Chain Applications Apr 3rd 2014
  High-performance SAR ADCs can offer amazing dynamic range and linearity at faster and faster sample rates. But how do you design the amplifier and interface at the analog inputs? LTspice IV can help. This video shows how to use LTspice to simulate the analog input interface of high-performance SAR ADCs. We will look ...

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LTspice IV: Extracting Switch Mode Power Supply Loop Gain in Simulation and Why You Usually Don't Need To

Mike Engelhardt - Simulation Development Mar 3rd 2014
The gain of a negative feedback loop needs to fall with frequency below unity before too much phase shift occurs unless your aim actually is to make an oscillator[1]. This idea can be applied to the stability analysis of a Switch Mode Power Supply(SMPS). Even though a SMPS is an intrinsically non-linear circuit with no small- ...

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LTspice IV: AC Analysis

Simon Bramble - Field Applications Engineer Feb 13th 2014
  Sometimes the frequency response of a circuit is more important than looking at the individual voltages or currents at a specific part of the schematic. LTspice IV can help you achieve this with its AC analysis function. This video shows you how to perform a basic AC analysis in LTspice as well as point out some capabilities ...

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LTspice IV: Integrating Noise Over a Bandwidth

Gabino Alonso Dec 19th 2013
LTspice IV can perform .noise analysis of a circuit, where the noise voltage density (V/√Hz) for 1Hz bandwidth) can easily be plotted for the output noise, input noise or for any noisy component like a resistor, diode or transistor. However, you can also easily integrate noise over a selected bandwidth in a .noise analysis. To ...

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LTspice IV: Stability of Op Amp Circuits

Kris Lokere - Signal Chain Applications Nov 6th 2013
  We all know that feedback circuits can oscillate. We may even know some tricks of how to fix it. But wouldn’t it be nice if our simulation tool could show us exactly what is happening, and why? This video illustrates how to use the .AC analysis to look at open loop gain and phase of operational amplifier ...

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LTspice IV: Computing the Average or RMS Value of a Trace

Gabino Alonso Nov 6th 2013
The LTspice IV waveform viewer can integrate a trace to produce the average or RMS value over a given region. To integrate a trace in the waveform viewer: Zoom in to the region of interest. Hold down the control key and click the label of the trace you want to integrate. Based on the physical units of the data trace, ...

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LTspice IV: Using the .STEP Command to Perform Repeated Analysis

Gabino Alonso Oct 7th 2013
There are two ways to examine a circuit in LTspice IV by changing the value for a particular parameter: you can either manually enter each value and then resimulate the circuit to view the response, or use the .step command to sweep across a range of values in a single simulation run.The .step command causes an analysis to be ...

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What Is The LTpowerCAD Design Tool and How Is It Different From LTspice?

Henry Zhang - Applications Manager, Power Products Sep 27th 2013
Today’s electronics systems require an increasing number of power rails and supply solutions, with the load range from a few mA for standby supply to over 100A for ASIC or FPGA core voltage regulators. It is important to have the appropriate solutions for the targeted applications and meet specified performance requirements, ...

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LTspice IV: Annotating Schematic & Waverform Plots

Gabino Alonso Sep 4th 2013
Adding informative comments to a schematic using text is very useful. However, there are times when adding a line, rectangle, circle or arc to a schematic can better illustrate a circuit. A classic example is highlighting a transformer core using two lines. In LTspice IV these graphical annotations are available under Draw in ...

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LTspice IV: Parametric Plots

Gabino Alonso Aug 6th 2013
Plotting results in LTspice IV is as easy as clicking on a node to show voltage, or a component to show current—the trace is then displayed in the waveform viewer. In transient analysis, the horizontal axis defaults to showing time, but you can always change the horizontal axis to show other quantities (such as current) ...

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LTspice IV: Importing & Exporting Data

Gabino Alonso Jul 18th 2013
The LTspice IV waveform viewer is a handy way to perform basic measurements, but there are times when you need to export data from, or import data into LTspice to further evaluate a circuit. To export waveform data to an ACSII text file: Click to select the waveform viewer Choose Export from the File menu. Select the traces ...

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LTspice IV: Piecewise Linear (PWL) Functions for Voltage & Current Sources

Gabino Alonso Jun 10th 2013
Piecewise linear (PWL) functions are used to construct a waveform from a series of straight line segments connecting points defined by the user in LTspice IV. Since PWL functions are useful in creating custom waveforms, they are typically used in defining voltage or current sources. To add a PWL function to a voltage or current ...

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LTspice IV: Noise Simulations

Tyler Hutchison - Applications Engineer May 7th 2013
  LTspice IV can perform frequency domain noise analysis which takes into account shot, thermal and flicker (1/f) noise. The resulting noise density (in units of volts per square root hertz) can then be plotted to aid in circuit analysis and understanding. This video covers how to setup a .noise simulation in LTspice ...

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LTspice IV: Undocumented Shortcuts

Gabino Alonso May 1st 2013
There are several undocumented shortcuts in LTspice IV that you might find useful: Alt + left-click on a label, V(n008), in the waveform viewer to highlight that particular net in the schematic editor. To route wires at an angle, hold down Ctrl key as you draw them. Text with a preceding underscore character, e.g., “_FAULT”, ...

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LTspice IV: Keyboard Shortcuts

Gabino Alonso Apr 15th 2013
Keyboard shortcuts are an alternate way to invoke one or more commands in LTspice IV that would otherwise only be accessible by clicking through the menu or toolbar. You can view these shortcuts for the schematic editor by choosing: Tools > Control Panel > Drafting Options and clicking Hot Keys. Hot Keys can be reprogrammed ...

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Simulating Power Planes with LTspice IV

Michael Jones Apr 8th 2013
When designing Power Distribution Networks (PDN) it is common to use SPICE models to represent the planes. High-end designs use 2D/3D electronic magnetic modeling tools to extract SPICE models. However, there are times when a simple spice model will suffice, or you may not always have access to very expensive 2D/3D modeling ...

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LTspice IV: Evaluating Electrical Quantities

Gabino Alonso - Strategic Marketing Apr 19th 2012
  Utilizing LTspice IV waveform viewer to analyze a circuit and perform basic measurements is very useful. However there are times where you need to evaluate a circuit with a numerical analysis. For these circumstances .MEASURE statements can be very powerful in evaluating user-defined electrical quantities. .MEASURE ...

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LTspice IV: Stepping Parameters

Gabino Alonso - Strategic Marketing Feb 9th 2012
  Plotting voltages or currents in a LTspice IV simulation is important but so is varying a parameter in a device or model so that you can compare performance and develop your circuit intuition. There are two ways to examine a circuit by changing the value of a parameter. You can either manually enter each value then ...

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LTspice IV: Adding Third-Party Models

Gabino Alonso - Strategic Marketing Oct 5th 2011
  LTspice IV supplies many device models to include discrete like transistors and MOSFET models. Nevertheless, there are also many third-party models from manufacturers that are available that you could add to your LTspice IV circuit simulations. These third-party SPICE models are described with a .MODEL and .SUBCKT ...

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LTspice IV: Using Transformers

Gabino Alonso - Strategic Marketing Aug 25th 2011
  Transformers and coupled inductors are key components in many switching regulator designs to include flyback, forward and SEPIC converters. They perform critical function in providing an isolation barrier, enabling high step-down or step-up ratios and accommodating multiple or inverting outputs. Although it is possible ...

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LTspice IV: Waveform Viewer

Gabino Alonso - Strategic Marketing Jul 22nd 2011
  LTspice IV includes an integrated waveform viewer that in combination with the schematic editor provides an easy way to display and review simulation data. This means that if you click on an object in the schematic editor, the voltage on that wire or current through that component will be plotted on a waveform viewer ...

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LTspice IV: Schematic Editor

Gabino Alonso - Strategic Marketing Apr 28th 2011
  Unlike many schematic capture programs, LTspice IV schematic editor was written explicitly for running SPICE simulations. This means that if you click on an object, the default behavior is to plot the voltage on that wire or current through that component, not select the object for editing. Hence, the first couple ...

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LTspice IV: Overview

Gabino Alonso - Strategic Marketing Mar 4th 2011
  LTspice IV is a high performance Spice III simulator, schematic capture and waveform viewer with enhancements and models for easing the simulation of switching regulators. Our enhancements to Spice have made simulating switching regulators extremely fast compared to normal Spice simulators, allowing the user to view ...

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