LTspice Getting Started Guide
User Manual:
Open the PDF directly: View PDF 
.
Page Count: 53
| Download | |
| Open PDF In Browser | View PDF |
SwitcherCAD III/LTspice Getting Started Guide Copyright © 2008 Linear Technology. All rights reserved. 2 Benefits of Using SwitcherCAD III/LTspice Stable SPICE circuit simulation with Outperforms pay-for options LTspice is also a great schematic capture Fast simulation of switching mode power supplies (SMPS) Unlimited number of nodes Schematic/symbol editor Waveform viewer Library of passive devices Steady state detection Over 1100 macromodels of Turn on transient Linear Technology products 500+ SMPS Step response Efficiency / power computations Advanced analysis and simulation options Not covered in this presentation © 2008 Linear Technology 3 How Do You Get SwitcherCAD III/LTspice Go to http://www.linear.com/software Left click on download SwitcherCAD III/LTspice Register for a new MyLinear account to receive updates if you have not done so already © 2008 Linear Technology Getting Started Copyright © 2008 Linear Technology. All rights reserved. 5 Getting Started using SwitcherCAD III/LTspice Use one of the 100s of demo circuits available on linear.com Use a pre-drafted test fixture (JIG) Reviewed by Linear Technology’s Factory Applications Group Provides a good starting point Use the schematic editor to create your own design LTspice contains macromodels for most LTC power devices © 2008 Linear Technology 6 Demo Circuits on linear.com Go to http://www.linear.com Enter root part number in the search box (e.g. 3411) Select Simulate Tab Follow the instructions provided If you do not find a demo circuit of interest, use a pre-drafted test fixture – covered next Download LTspice Download Demo Circuit Complete list of demo circuits available at www.linear.com/democircuits © 2008 Linear Technology 7 Demo Circuit 9 Designed and Reviewed by Factory Apps Group To run a demo circuit jump to the Run and Probe a Circuit in LTspice section What if I cannot find a demo circuit? 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 © 2008 Linear Technology 8 Getting Started using SwitcherCAD III/LTspice Use one of the 100s of demo circuits available on linear.com Use a pre-drafted test fixture (JIG) Reviewed by Linear Technology’s Factory Applications Group Provides a good starting point Use the schematic editor to create your own design LTspice contains macromodels for most LTC power devices © 2008 Linear Technology 9 Pre-Drafted Test Fixture (JIG) Used for testing models during development Provides a draft starting point Not reviewed by Linear Technology’s factory applications team 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 © 2008 Linear Technology 10 Start with a New Schematic New Schematic Left click on the New Schematic symbol in the Schematic Editor Toolbar © 2008 Linear Technology 11 Add a Macromodel & Opening Test Fixture Add Component Left click on the Component symbol in the Schematic Editor Toolbar Enter “root” part to search for the model (e.g. 3411) Left click on Open this macromodel’s test fixture To run a test fixture, jump to the Run and Probe a Circuit in LTspice section © 2008 Linear Technology 12 Getting Started using SwitcherCAD III/LTspice Use one of the 100s of demo circuits available on linear.com Use a pre-drafted test fixture (JIG) Reviewed by Linear Technology’s Factory Applications Group Provides a good starting point Use the schematic editor to create your own design LTspice contains macromodels for most LTC power devices © 2008 Linear Technology Draft a Design Using the Schematic Editor Copyright © 2008 Linear Technology. All rights reserved. 14 Start with a New Schematic New Schematic Left click on the New Schematic symbol in the Schematic Editor Toolbar LTspice is also a great schematic capture © 2008 Linear Technology 15 Add a Linear Technology Macromodel Add Component Left click on the Component symbol in the Schematic Editor Toolbar Enter “root” part to search for the model (e.g. 3411) Left click on OK © 2008 Linear Technology 16 Getting the Latest Datasheet Use the macromodel’s shortcuts to download the Datasheet as a reference for your design Hold Ctrl key and right click (Ctrl – right click) over the LT macromodel’s symbol Left click on Go to Linear website for datasheet on the dialog box that appears You can also open the macromodel's test fixture as a draft starting point © 2008 Linear Technology 17 Adding Circuit Elements Place Diode Place Inductor Place Capacitor Place Resistor Rotate Mirror Left click on the desired component in the Schematic Editor Toolbar Left click on Rotate or Mirror to adjust orientation Alternate you can also use Ctrl – R and Ctrl – M key shortcuts Move the mouse to the position you want to place it Left click to place it To cancel or quit a component type, click the right mouse button © 2008 Linear Technology 18 Adding Sources, Loads & Additional Circuit Elements Left click on the Component symbol in the Schematic Editor Toolbar Search directory structure for desired circuit element (e.g. load and voltage) Left click on OK Move the mouse to the position you want to place it Left click to place it Additional Circuit Elements Like Sources and Loads © 2008 Linear Technology 19 Highlights of Additional Circuit Elements Left click on the Component symbol in the Schematic Editor Toolbar for a directory of additional circuit elements: Lossy transmission line Arbitrary behavioral source Bipolar transistor Voltage dependent voltage Voltage controlled switch Current dependent current Lossless transmission line Voltage dependent current Uniform RC-line Current dependent voltage Independent voltage source Independent current source Current controlled switch JFET transistor Subcircuit Mutual inductance MESFET transistor MOSFET transistor …many more © 2008 Linear Technology 20 Drawing Lines and Labeling Nodes Draw Wire Place Ground Label Node Do not forget to place a ground in your design, it is required for simulation! Lines Left click on the Draw Wire in the Schematic Editor Toolbar Left click a blue box (terminal) Define the line’s path with a left click over intermediate points Left click on another blue box (terminal) © 2008 Linear Technology 21 Editing Circuit Elements Delete Duplicate Move Drag Undo Redo Left click on the desired editing option Left click on the circuit element To organize your layout, use the Drag option to move circuit elements around and to adjust lines between terminals © 2008 Linear Technology 22 Editing Circuit Elements Attributes Right click on the component symbol to modify attributes Right click on the text next to the component to edit the visible attribute and label Pointer will turn into a text caret © 2008 Linear Technology 23 Use Labels to Specify Units in Circuit Elements Attributes K = k = kilo = 103 MEG = meg = 106 G = g = giga = 109 T = t = terra = 1012 M = m = milli = 10-3 U = u = micro = 10-6 N = n = nano = 10-9 P = p = pico = 10-12 F = f = femto = 10-15 Hints Use MEG to specify 106, not M Enter 1 for 1 Farad, not 1F © 2008 Linear Technology 24 Circuit Elements Database Some components have an available database of manufacturers’ attributes Resistors, capacitors, inductors, diodes, Bipolar transistors, MOSFET transistors, JFET transistors Independent voltage and current sources To configure a component to a manufacture’s attributes Right click on the component symbol Left click on Select… or Pick New… Left click on a selected device Left click on OK © 2008 Linear Technology 25 Editing Voltage Sources and Loads Voltage Source Right click the voltage symbol Enter DC voltage value and (optional) Series Resistance Left click on OK Load (current) Right click on the load symbol Enter DC current value Left click on OK © 2008 Linear Technology 26 Summary of Schematic Editor Toolbar Place Circuit Element Place Diode Place Inductor Place Capacitor Place Resistor Label Node Place Ground Draw Wire Delete Duplicate Paste b/t Schematics © 2008 Linear Technology Find Move Drag Undo Redo Rotate Mirror Place Comment Place SPICE directive Run and Probe a Circuit Copyright © 2008 Linear Technology. All rights reserved. 28 Simulation Commands To run a simulation, specify the type of analysis to be performed There are six different types of analyses: Transient analysis Small signal AC DC sweep Noise DC transfer function DC operating point More information on simulation and dot commands are available in SwitcherCAD III/LTspice User Guide Simulation commands are placed on the schematic as text Called dot commands © 2008 Linear Technology 29 Editing Simulation Commands Left click on Simulation menu Left click on Edit Simulation Cmd As a starting point in a simulation Left click on Transient tab Enter a Stop Time You may need to adjust this again later Select OK © 2008 Linear Technology Demo Circuits and Test Fixtures have predefined Simulations Commands 30 Running a Circuit Run If model is not found please Sync Release under Help menu to update LTspice © 2008 Linear Technology 31 Probing a Circuit & Waveform Viewer Left click on any wire to plot the voltage on the waveform viewer Voltage probe cursor Left click on the body of the component to plot the current on the waveform viewer Convention of positive current is in the direction into the pin Current probe cursor © 2008 Linear Technology 32 Probing a Demo Circuit and Test Fixture Demo Circuits and Test Fixtures have INs and OUTs clearly labeled to help you quickly select them To view the waveform left click on IN and OUT Left Click Here for Input Waveform © 2008 Linear Technology Left Click Here for Output Waveform 33 Voltage Differences Across Nodes Left click and hold on one node and drag the mouse to another node Red voltage probe at the first node Black probe on the second Differential voltages are displayed in the waveform viewer © 2008 Linear Technology 34 Plot Planes Multiple plot panes can be displayed on one window to allow better separation between traces permitting different traces to be independently autoscaled Right click in the waveform pane Select Add Plot Pane Left click and hold to drag a label to a new plot pane © 2008 Linear Technology 35 Zooming In and Out in the Waveform Viewer To zoom in Left click and hold as you drag a box about the region you wish to zoom in then release To zoom out Right click and select Zoom to Fit or Zoom Back Zoom In Pan Zoom Out Autoscale © 2008 Linear Technology 36 Measuring VRipple, IRipple and Time (Frequency) Drag a box about the region you wish to measure (peak to peak over a period) Left click and hold to drag a box over the portion of interest View the lower left hand side of the screen To avoid resizing, shrink your box before you let go of the left mouse click or use the Undo command in the Edit menu To view SMPS voltage ripple you will need to zoom into a narrow section since waveform is initially compressed to full range © 2008 Linear Technology 37 Average/RMS Current or Voltage Calculations Hold down Ctrl and left click on the I or V trace label in the waveform viewer © 2008 Linear Technology 38 Instantaneous & Average Power Dissipation Instantaneous Power Dissipation Hold down the ALT key and left click on the symbol of the component Pointer will change to a thermometer Plotted in units of Watts Average Power Dissipation Hold down the Ctrl key and left click on the trace label power dissipation waveform © 2008 Linear Technology Generating a BOM and Efficiency Report Copyright © 2008 Linear Technology. All rights reserved. 40 Bill of Materials (BOM) Left click on View menu Left click on Bill of Materials © 2008 Linear Technology 41 Computing Efficiency of SMPS Circuits Left click on Simulate menu Left click on Edit Simulation Cmd Left click on Stop simulating if steady state is detected Automatically detect the steady state by checking the internal state of the macromodels Rerun simulation © 2008 Linear Technology Automatic detection of steady state may not work – steady state detection may be too strict or lenient 42 Viewing Efficiency Report Left click on Simulate menu Left click on Efficiency Report © 2008 Linear Technology Simulate a Transient Response in a SMPS Advanced Topic Copyright © 2008 Linear Technology. All rights reserved. 44 Use a Pulsed Function as a Transient Response Load Insert a current source load Left click on the Component symbol in the Schematic Editor Toolbar Select load (or load2) circuit element and configure as pulsed Left click on OK Configure load as a pulsed function (covered next) Steps current from initial to pulsed value and back Run and review results © 2008 Linear Technology 45 Configuring Load as a Pulse Function Right click on the load (or load2) component Select Pulse Modify the Attributes I1 = Initial value I2 = Pulsed Value Tdelay = Delay Tr = Rise time Tf = Fall time Ton = On time Tdelay needs to be adequate so that Tperiod = Period the device is in steady state and out Ncycles = Number of cycles of startup before the load step occurs Omit for free running You may need to un-click Stop simulating if steady state is detected and specify an end time in Edit Simulation Cmd under the Simulate menu © 2008 Linear Technology Simulate a Transformer Advanced Topic Copyright © 2008 Linear Technology. All rights reserved. 47 Simulating a Transformer Draw each winding of the transformer as an individual inductor Couple inductors with a mutual inductance statement Add a SPICE directive of the form K1 L1 L2 L3 ... 1 to the schematic Left Click on Edit then SPICE Directive Inductors in a mutual inductance will be drawn with a phasing dot Start initially with a mutual coupling coefficient equal to 1 K statement coupling the windings For more information check out LTC1871 demo circuit and page 23-24 of September 2006 LT Magazine at www.linear.com 1:3 turns ration gives a 1:9 inductance ratio © 2008 Linear Technology Note: winding inductance ratio is the square of the turns ratio Additional Information and Support Copyright © 2008 Linear Technology. All rights reserved. 49 Reminder to Periodically Sync Release Update your release of LTspice to get the latest Software updates Models and examples Sign up for Linear Insider via MyLinear (www.linear.com) for email news and updates List of changes are available in the changelog.txt that is located in your LTspice root directory (C:\Program Files\LTC\SwCADIII) © 2008 Linear Technology 50 Built-in Help System Left Click on Help menu and then Help Topics To print out a hardcopy, download user guide at http://LTspice.linear.com/software/scad3.pdf © 2008 Linear Technology 51 Emailing Comments and Signing up for Linear Insider © 2008 Linear Technology 52 Customer Support Linear Technology customers can obtain support by Calling your local field applications engineer http://www.linear.com/contact/ Calling +1 (408) 432 – 1900 for factory application support Additional support (not related to Linear Technology circuits or models support) Built-in help topics & User Manual Independent LTspice users’ group (search messages) Simulation with the supplied models is fully supported All bug reports are appreciated and will be resolved © 2008 Linear Technology 53 Independent LTspice Users’ Group The group has a section of files and messages with additional tutorials, libraries, and examples http://groups.yahoo.com/group/LTspice/ Join LTspice Users’ Group Email LTspice-subscribe@yahoogroups.com © 2008 Linear Technology Subject=Subscribe
Source Exif Data:
File Type : PDF File Type Extension : pdf MIME Type : application/pdf PDF Version : 1.4 Linearized : Yes Tagged PDF : Yes XMP Toolkit : Adobe XMP Core 4.0-c316 44.253921, Sun Oct 01 2006 17:14:39 Producer : Acrobat Distiller 8.1.0 (Windows) Creator Tool : Acrobat PDFMaker 8.1 for PowerPoint Modify Date : 2008:03:12 15:13:11-07:00 Create Date : 2008:03:12 15:13-07:00 Metadata Date : 2008:03:12 15:13:11-07:00 Format : application/pdf Creator : Gabino Alonso Title : LTspice Getting Started Guide Document ID : uuid:88a5a487-b097-4849-afa8-9cd0bba01f6b Instance ID : uuid:585387b9-7179-4191-a2f4-8e134b5e9919 Company : Page Count : 53 Page Layout : SinglePage Author : Gabino AlonsoEXIF Metadata provided by EXIF.tools