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Copyright © 2007 Linear Technology. All rights reserved.
LTspice Getting Started Guide
2LTspice Getting Started Guide
Why Use LTspice?Stable SPICE circuit simulation with
Unlimited number of nodesSchematic/symbol editorWaveform viewerLibrary of passive devices
Fast simulation of switching mode power suppliesSteady state detectionTurn on transientStep responseEfficiency / power computations
Advanced analysis and simulation optionsNot covered in this presentation
Outperforms pay-for options
Over 1100 macromodels ofLinear Technology products500+ SMPS
Over 1100 macromodels ofLinear Technology products500+ SMPS
LTspice is also a great schematic captureLTspice is also a great schematic capture
3LTspice Getting Started Guide
How Do I Get LTspice?Go to http://www.linear.comSelect “Design Support” and then “Design Simulation”Follow the instruction to install
How Do I Get Started Using LTspice?
5LTspice Getting Started Guide
How Do I Get Started using LTspice?1. Use one of the 100’s demo circuit available on linear.com
Designed and Reviewed by Factory Apps Group
2. Use a pre-drafted test fixture (JIG)Provides a good starting pointUsed in testing models during development
3. Use the graphic editor to create your own design using the macro models provided
LTspice contains models for most LTC power devices
You can also check out LTspice capabilities using the education examples available on C:\Program Files\LTC\SwCADIII\examples\Educational
You can also check out LTspice capabilities using the education examples available on C:\Program Files\LTC\SwCADIII\examples\Educational
6LTspice Getting Started Guide
How Do I Get Started using LTspice?1. Use one of the 100’s demo circuit available on linear.com
Designed and Reviewed by Factory Apps Group
2. Use a pre-drafted test fixture (JIG)Provides a good starting pointUsed in testing models during development
3. Use the graphic editor to create your own design using the macro models provided
LTspice contains models for most LTC power devices
7LTspice Getting Started Guide
Demo Circuits on linear.com
Download LTspice
Download Demo Circuit
8LTspice Getting Started Guide
Demo CircuitDesigned and Reviewed by Factory Apps Group
It remains the customer's responsibility to verify proper and reliable operation in the actual applicationComponent substitution and printed circuit board layout may significantly affect circuit performance or reliability
What if I cannot find a demo circuit?What if I cannot find a demo circuit?
9LTspice Getting Started Guide
How Do I Get Started using LTspice?1. Use one of the 100’s demo circuit available on linear.com
Designed and Reviewed by Factory Apps Group
2. Use a pre-drafted test fixture (JIG)Provides a good starting pointUsed in testing models during development
3. Use the graphic editor to create your own design using the macro models provided
LTspice contains models for most LTC power devices
10LTspice Getting Started Guide
Start with a New SchematicSelect File and New Schematic
Will open up a black layout screen
11LTspice Getting Started Guide
Add a ComponentUse Add a Component or F2
Take a moment to review all the components!
12LTspice Getting Started Guide
Selecting Model & Opening Test Fixture1. Use the “root” part to search for the model
i.e. 34112. Select “Open this macromodel’s test fixture
1. Enter 3411
2. Select
13LTspice Getting Started Guide
Pre-Drafted Test FixtureProvides a good starting point
Used in testing models during development
It remains the customer's responsibility to verify proper and reliable operation in the actual application
Printed circuit board layout may significantly affect circuit performance or reliability
It remains the customer's responsibility to verify proper and reliable operation in the actual application
Printed circuit board layout may significantly affect circuit performance or reliability
14LTspice Getting Started Guide
How Do I Get Started using LTspice?1. Use one of the 100’s demo circuit available on linear.com
Designed and Reviewed by Factory Apps Group
2. Use a pre-drafted test fixture (JIG)Provides a good starting pointUsed in testing models during development
3. Use the graphic editor to create your own design using the macro models provided
LTspice contains models for most LTC power devices
15LTspice Getting Started Guide
Use the Graphic Editor to Create Your Own DesignSelect the ModelUse the menu to design you circuit
=
Cus
tom
Des
ign
Also Great for drawing schematics
for customers
Additional ComponentsLike Sources
& Loads
16LTspice Getting Started Guide
Schematic EditingPlace Circuit Element
Place DiodePlace Inductor
Place CapacitorPlace Resistor
Label NodePlace Ground
Draw Wire
MoveDragUndo
RedoRotate
MirrorPlace Comment
Place SPICE directive
DeleteDuplicate
Paste b/t SchematicsFind
Zoom InPan
Zoom OutAutoscale
17LTspice Getting Started Guide
Editing ComponentsComponents’ attributes can be edited by pointing at the component with the mouse and right clicking
You can also edit the visible attribute and label by pointing at the text with the mouse and then right clicking
Mouse cursor will turn into a text caret
You can also edit the visible attribute and label by pointing at the text with the mouse and then right clicking
Mouse cursor will turn into a text caret
18LTspice Getting Started Guide
Component DatabaseComponents such as
Resistors, capacitors, inductors, diodes, Bipolar transistors, MOSFET transistors, JFET transistorsIndependent voltage and current sources
can access a database of know devices
19LTspice Getting Started Guide
Test Fixture Shortcut with LT MacromodelsPlace the mouse over the LT macromodel’s symbolHold down the control key, and click the right mouse buttonA dialog box will appear that will allow you to
Open the test fixtureGo to Linear website for the datasheet
How Do You Run and Probe a Circuit in LTspice?
21LTspice Getting Started Guide
Running Demo Circuit
Select run“Running Man” logo on menu
RunRun
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Current probe cursor
Waveform ViewerLTspice has an integrated waveform viewer 1. Plot the voltage on any wire by
simply point and click
2. Plot the current through any component with two connections by clicking on the body of the component
R, C, L
Convention of positive current is in the direction into the pin
Voltage probe cursor
23LTspice Getting Started Guide
Probing a Demo Circuit
All Demo Circuits have INs and OUTs clearly labeled to help you quickly select themSelect the waveform of a node by clicking on IN and OUT
Click Here for Output Waveform
Click Here for Output Waveform
Click Here for Input
Waveform
Click Here for Input
Waveform
24LTspice Getting Started Guide
Zooming In and Out on a Waveform
Using the mouse to zoom in and outDrag a box about the region you wish to see drawn larger
Right click and select “Zoom to Fit” to zoom back
25LTspice Getting Started Guide
Measuring V, I and Time in the Waveform1. Drag a box about the region you wish to measure
Hold the left click down
2. View the lower left hand side of the screen 3. Shrink your box before you let go of the left mouse click or
use the undo command on top to resize
26LTspice Getting Started Guide
Voltage Differences Across NodesClick on one node and drag the mouse to another node
Red voltage probe at the first nodeBlack probe on the second
Will provide differentially plot of the voltages
27LTspice Getting Started Guide
Average/RMS Calculations
Average & RMS Current or VoltageControl - left click the I or V trace label in the waveform view
28LTspice Getting Started Guide
Instantaneous & Average Power Dissipation
Instantaneous Power Dissipation Hold down the Alt key and left clickon the symbol of the componentPlotted in units of Watts
Average Power Dissipation Control - left click the power Dissipation trace label in the waveform view
Generating a BOM and Efficiency Report
30LTspice Getting Started Guide
BOMUnder View select Bill of Material
Displayed on DiagramPaste to Clipboard
31LTspice Getting Started Guide
Computing EfficiencyTo compute efficiency of SMPS circuits:
Check the "Stop simulating if steady state is detected" on the Edit Simulation Command editorRerun simulationUse the menu command View=>Efficiency Report
Automatic detection of steady state may not always work –criteria for steady state detection may be too strict or too lenient
Automatic detection of steady state may not always work –criteria for steady state detection may be too strict or too lenient
32LTspice Getting Started Guide
Viewing Efficiency Report
Simulate a Transient Response?
34LTspice Getting Started Guide
Current Load and Pulse FunctionYour can simulate a load with a Resistor or Current loadIn particular the Pulse function in a current load is helpful intransient response analysis
Steps a current load from one value to another
35LTspice Getting Started Guide
Edit the Current Load to a Pulse FunctionRight click on the current loadSelect PulseModify the Attributes
More Information and Support
37LTspice Getting Started Guide
Reminder to Periodically Sync Release
It is important to sync your release of LTspice once a month to get the latest
Software update and bug fixModelsSample circuits and examples
38LTspice Getting Started Guide
Built-in Help SystemSelect F1 for help menu
39LTspice Getting Started Guide
Paper ManualDownload the pdf of the help pages from:
http://LTspice.linear.com/software/scad3.pdf
40LTspice Getting Started Guide
Emailing SupportMake sure you’re using the current version with Field sync.
41LTspice Getting Started Guide
LTspice Support GroupThe group has a Files section with additional tutorials, libraries, and examplesVisit the user group
http://groups.yahoo.com/group/LTspice/
Join LTspice Yahoo GroupEmail [email protected]=Subscribe