4/20/2022
Getting Started with LTspice®
MARIO GONZALEZ
CHARLIE EL-KHOURY
IN PARTNERSHIP WITH ARROW
©2022 Analog Devices, Inc. All rights reserved.
LTspice
Free – Fast – Unlimited
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One Analog Guru’s Opinion on SPICE in 1996
“I hurled this computer to
its doom from atop
National’s 3-story parking
garage. As the dust settled,
I knew that computer
would never lie to me
again!”
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This was in 1996.
But simulators have
evolved immensely.
(Even Bob Pease
mellowed out about
this in later years.)
©2022 Analog Devices, Inc. All rights reserved.
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4/20/2022
LTspice – What’s the Point?
https://www.youtube.com/watch?v=x6TrbD7-IwU (play to 2:30)
►
Value of a simulator
►
Is it a good sanity check? No
►
Is it how you verify a design? No
►
The point in simulation is so you
understand your circuit better
►
Intuition is the most important part of
engineering
©2022 Analog Devices, Inc. All rights reserved.
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Goal of LTspice – Develop Circuit Intuition Through Simulation
► Simulation
techniques are an essential part of an electronic circuit design
 Non-bench discovery
► Provides





insight into the operation of a designed circuit prior to its being prototyped
Design optimization
Boundary conditions
Device tolerances
Verification of requirements
“What if” scenarios that would be difficult or impossible to undertake on a real circuit
The key to simulation is the speed with which you can understand your circuit, its
correctness, and its limitations before going into the lab to prototype and test
SPICE = Simulation Program with Integrated Circuit Emphasis
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Design Verification is Done in the Laboratory - Prototype &
Bench Test
► Verify
proper and reliable operation in the actual application
 Simulation is typical performance (production scatter and temperature behavior is never modeled)
 Printed circuit board layout may significantly affect circuit performance or reliability compared to
simulation results
There is a point of limiting return on simulation, get into the lab to
prototype and bench test sooner rather than later
Laboratory
Nirvana
Theory
5
Simulation
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Agenda
► Benefits
of LTspice
► Examples
► Using
the schematic editor
► Running
► Basic
and reference designs libraries
and probing a schematic
measurements and calculations
► Simulating
a transient response
► Homework
► Resources
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and support
©2022 Analog Devices, Inc. All rights reserved.
©2021
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What is LTspice?
► ADI’s
analog electronic circuit simulator
 Free
 No cost simulation platform designed for our customers and the engineering community
 *Not* licensed for use by semiconductor manufacturers
 Unlimited
 Draft and simulate circuits of unlimited size and content
 Unlimited hierarchy are supported
Even though LTspice is freeware, it
outperforms many pay-for options
 Fast
 Optimized macro-models for many ADI devices
 For example, switch mode power supplies simulate rapidly
©2022 Analog Devices, Inc. All rights reserved.
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How Do I Get LTspice?
► Go
to www.analog.com/LTspice
► Site
also contains useful links to:
 Demo Circuits (reference designs)
 Documentation
 Handout of shortcut keys
 Video Tutorials
 Technical Articles
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LTspice is a standalone application
that runs on your computer
©2022 Analog Devices, Inc. All rights reserved.
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How Do I Get Started Using LTspice?
► Use
one of the 1000’s of Demo Circuits available at analog.com
 Reviewed by product application engineers
► Use
a test fixture
 Provides a good starting point
► Create
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your own using the schematic editor
©2022 Analog Devices, Inc. All rights reserved.
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Demo Circuits Are Available on Product and Eval Board Pages
► Click
on “Tools & Simulations” to find reference LTspice circuit(s)
Demo Circuit
Available Models
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©2022 Analog Devices, Inc. All rights reserved.
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4/20/2022
Archive: Complete Collection of Demo Circuits
► Link
available on www.analog.com/LTspice
©2022 Analog Devices, Inc. All rights reserved.
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How Do I Get Started Using LTspice?
► Use
one of the 1000’s of Demo Circuits available at analog.com
 Reviewed by product application engineers
► Use
a test fixture
 Provides a good starting point
► Create
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your own using the schematic editor
©2022 Analog Devices, Inc. All rights reserved.
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Test Fixtures
► These
► Good
are “test jig circuits” used to validate macro-models
initial starting point for your schematic
 Simplified schematics (front page of the datasheet)
 Components may be “ideal” or encapsulated to simplify simulation and schematic
 May highlight fault events
Users may need to modify
based on requirements
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©2022 Analog Devices, Inc. All rights reserved.
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Opening a Test Fixture
► Complete
collection is available at ..\examples\jigs
Edit menu, select
“Component”
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Search for
macromodel
Click Here
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How Do I Get Started Using LTspice?
► Use
one of the 1000’s of Demo Circuits available at analog.com
 Reviewed by product application engineers
► Use
a test fixture
 Provides a good starting point
► Create
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your own using the schematic editor
©2022 Analog Devices, Inc. All rights reserved.
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Start With a New Schematic
► To
open a new schematic in LTspice, select File > New Schematic
Empty schematic
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©2022 Analog Devices, Inc. All rights reserved.
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Drafting Using the
Schematic Editor
EXAMPLE:
SINGLE POLE FILTER USING RC
NETWORK
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LTspice
Free – Fast – Unlimited
©2022 Analog Devices, Inc. All rights reserved.
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Opening a New Schematic (Ctrl-N)
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Adding Passives and Grounds
Ctrl+R to rotate
before placement
Use R, C, and G keys to
place resistors, capacitors
& ground symbols
Ctrl+E (echo) to
mirror before
placement
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To exit a symbol, select
Esc or right click
©2022 Analog Devices, Inc. All rights reserved.
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Adding a Voltage Source and Component Library
Use the ‘V’ keyboard shortcut or
the following
Type “Voltage”
Click “OK”
Edit menu, select
“Component”
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Wire Up the Circuit
F3 or select
“Wire” button
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Wire Up the Circuit
► Wire
up the circuit
Left-Click ground
“Pull” wire up through the source
Left-Click here
to anchor
“Pull” wire through the resistor
Left-Click here
to anchor
“Pull” wire down through the capacitor
Left-Click here
to anchor & finish
Press the ESC key or
right click to stop
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©2022 Analog Devices, Inc. All rights reserved.
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Add Net Labels
F4 or select
“Label Net”
Enter net name
Place on wire
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Specify the name so an arbitrary
one isn't generated for the node
©2022 Analog Devices, Inc. All rights reserved.
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Component Values
Right-click on
symbol
Or Right-click on
value
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Units for Component Parameters
►M
= m = milli = 10-3
►K
►U
= u = micro = 10-6
► MEG
►N
= n = nano =
10-9
►P
= p = pico = 10-12
►F
= f = femto =
10-15
= k = kilo = 103
= meg = 106
►G
= g = giga = 109
►T
= t = tera = 1012
Hints
 Use MEG (or meg) to specify 106, not M
 Enter 1 for 1 Farad, not 1F
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©2022 Analog Devices, Inc. All rights reserved.
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Editing Components
► Right-Click
on the component to edit attributes
► You
can also edit the visible attribute and label by pointing at the text with the
mouse (cursor will change to a text icon) and right-clicking
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Component Database
► Available
for resistors, capacitors, inductors, diodes, bipolar transistors, MOSFET
transistors, and JFET transistors
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Voltage Source Parameters
Click
“Advanced”
Right-click source
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Voltage Source PULSE Parameters
Translates to PULSE(0 5 0 1u 1u 10m 20m 3) on schematic
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©2022 Analog Devices, Inc. All rights reserved.
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Zooming In and Out, Pan, & Autoscale
Zoom to Rectangle
or Ctrl+Z
Pan or Click Hold
Autoscale or Space
Zoom Back or Ctrl+B
Zoom In or Out -> Scroll Wheel
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©2022 Analog Devices, Inc. All rights reserved.
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Drag & Move
Move or F7
Draw box or
Click on Component or Wire
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F8 or Drag
(keep element wired)
Reposition and Click to Place
©2022 Analog Devices, Inc. All rights reserved.
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Edit Simulation Command – Transient Analysis
Select “Edit
simulation Cmd”
in Simulate menu
Enter in
60m
Click to place
on schematic
Click OK
►
Performs the DC analysis to establish a DC operating point, then increments the time step and
calculates the voltage and current values of the respective nodes
►
Useful for start up, stability, and transient analysis
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©2022 Analog Devices, Inc. All rights reserved.
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Completed Schematic
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©2022 Analog Devices, Inc. All rights reserved.
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Summary of Shortcuts (Toolbar is Available in Windows
Version)
Zoom In [scroll wheel]
Pan [click hold]
Zoom Out [scroll wheel]
Autoscale [space]
Delete [Del or F5]
Duplicate [Ctrl+C]
Paste b/t Schematics [Ctrl+V]
Find [Ctrl+F]
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Place Circuit Element [F2]
Place Diode [D]
Place Inductor [L]
Place Capacitor [C]
Place Resistor [R]
Label Node [F4]
Place Ground [G]
Draw Wire [F3]
Toolbar is handy but
keyboard shortcuts are
more efficient
Move [F7]
Drag [F8]
Undo [F9]
Redo [Shift+F9]
Rotate [Ctrl+R]
Mirror [Ctrl+E]
Place Comment/text [T]
Place SPICE directive [S]
©2022 Analog Devices, Inc. All rights reserved.
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4/20/2022
Running and
Probing a Schematic
EXAMPLE:
SINGLE POLE FILTER USING RC
NETWORK
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LTspice
Free – Fast – Unlimited
©2022 Analog Devices, Inc. All rights reserved.
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Running the RC Circuit Simulation
► With
the schematic window active, click on the RUN button on the toolbar
Run
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©2022 Analog Devices, Inc. All rights reserved.
RCFilterTimeDomain.asc
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Probe Voltages
► Plot
the voltage on any wire by a simple point and click
Click here for output
waveform
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©2022 Analog Devices, Inc. All rights reserved.
RCFilterTimeDomain.asc
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Measurement Cursor
► In
the waveform window, left+click the mouse on the waveform name
Click to display
measurement
cursor. Click
and drag cursor
position.
To add a second
measurement cursor,
left+click again on the
waveform name
RCFilterTimeDomain.asc
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©2022 Analog Devices, Inc. All rights reserved.
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Probe Current
► Plot
the current through any component by clicking on the body of the component
Click here for resistor
current waveform
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©2022 Analog Devices, Inc. All rights reserved.
RCFilterTimeDomain.asc
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Adding Plot Pane
► Select
► Drag
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“Add Plot Pane” under the Plot Settings pull-down menu
and drop a waveform name into the new plot pane
©2022 Analog Devices, Inc. All rights reserved.
RCFilterTimeDomain.asc
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Alternate: Right Click on Waveform Viewer to Add Plot Pane
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©2022 Analog Devices, Inc. All rights reserved.
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AC Analysis
EXAMPLE:
SINGLE POLE FILTER USING RC
NETWORK
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LTspice
Free – Fast – Unlimited
©2022 Analog Devices, Inc. All rights reserved.
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Edit Simulation Command - AC Analysis
► Performs
small signal AC analysis
linearized about the DC operating
point
► Useful
for analysis of filters,
networks, stability analysis, and
noise considerations
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©2022 Analog Devices, Inc. All rights reserved.
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Simulating AC Analysis
Set voltage source to AC
amplitude of 1
(sets magnitude to 0dB)
Right-click on .tran
command and select
“AC Analysis”
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Run & Probe Output
Click here for
Bode plot
Click here to
Measure -3db
point
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©2022 Analog Devices, Inc. All rights reserved.
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Measure the -3db Point
-3dB point: 1/(2*pi*R*C) = 159Hz
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©2022 Analog Devices, Inc. All rights reserved.
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Running a
Simulation
and Analyzing
Circuit Performance
EXAMPLE:
DC/DC CONVERTER DEMO CIRCUIT
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LTspice
Free – Fast – Unlimited
©2022 Analog Devices, Inc. All rights reserved.
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Running a DC/DC Converter Simulation
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Viewing Voltage Waveforms
► Plot
the voltage on any wire by Left-Clicking it
 Tip: All Demo Circuits have INs and OUTs clearly labeled to help you quickly select them
Click here for
output
waveform
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Labeling - Trick
► Highlight
net from waveform viewer
 Alt-Left-Click on the label in the waveform viewer (i.e. V(n006)) and it will now highlight that
particular net on the schematic. You can also use the search function ( )
Alt-LeftClick
Net
Highlighted
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Viewing Differential Voltage Waveforms
► Left-Click
on one node and drag the mouse to another node
 Red voltage probe at the first node
 Black probe on the second
LTC3412A_DC_Load.asc
©2022 Analog Devices, Inc. All rights reserved.
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Viewing Differential Voltage Waveforms
► To
create a measurement reference node, Right-Click on the desired node and
select “Mark Reference”
 A black voltage probe is anchored to the selected node
► All
measurements in the circuit are now referenced to the node with the black
probe
► Hit
the ESC key to remove the reference mark
LTC3412A_DC_Load.asc
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©2022 Analog Devices, Inc. All rights reserved.
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Viewing Current Waveforms
► Plot
the current through any component by Left-Clicking on the body of the
component
 Current flowing into a node is defined as being positive
Click here for
inductor current
waveform
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Deleting Waveforms
► Method
#1: Right-Click on a trace label to be deleted
 Select “Delete this Trace”
 Deletes only the selected trace
LTC3412A_DC_Load.asc
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©2022 Analog Devices, Inc. All rights reserved.
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Deleting Waveforms
► Method
#2: If the plot window is active hotkey F5 is equivalent
 Cursor turns into scissors
 Left-Click on one or more trace labels to delete. ESC to quit
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Deleting Waveforms
► Method
#3: Plot the same waveform twice in succession
 Deletes all but that waveform
Click,
click
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Zooming In and Out on a Waveform
► In
the waveform window, use the mouse to zoom in and out. Click and drag a box
about the region you wish to see drawn larger
► Using
the toolbar, click on “Zoom full extents”, to zoom back out
Zoom Full Extents
LTC3412A_DC_Load.asc
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©2022 Analog Devices, Inc. All rights reserved.
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Measuring V, I and Time in the Waveform
(Measurement Using Cursors)
► Right-Click
► For
on the waveform name in the waveform window
“Attached Cursor”, select “1st & 2nd”
► Position
cursors to make desired measurements
1.
2.
3.
Result
LTC3412A_DC_Load.asc
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©2022 Analog Devices, Inc. All rights reserved.
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Measuring V, I and Time in the Waveform
(Measurement Using Zoom Window)
►
Drag a box about the region you wish to measure
 Left-Click, drag, and hold
►
View the lower left corner of the window for the status bar. The dx and dy measurement data is
displayed here.
►
Use Undo from the File menu or press “F9”
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Viewing Wire Current Waveforms
► Plot
the current through any wire by Alt+Left-Clicking on the wire
 An ammeter will appear to indicate that the wire current will be displayed
LTC3412A_DC_Load.asc
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©2022 Analog Devices, Inc. All rights reserved.
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Average & RMS Calculations
► Average
& RMS Current, Voltage, or Power Dissipation
 Calculated only for the visible area of the plot window
► Click
on inductor L1 to display the inductor current waveform
 Ctrl+Left-Click the I(L1) trace label in the waveform view
Example:
Measure average and RMS
current for inductor in
LTC3412A circuit. Zoom in
as shown for this
waveform.
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©2022 Analog Devices, Inc. All rights reserved.
LTC3412A_DC_Load.asc
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Instantaneous & Average Power Dissipation
► Instantaneous
Power Dissipation
 Alt+Left-Click on the symbol of the LTC3412A
 Waveform is displayed in units of Watts
► Average
Power Dissipation
 Click, hold, and drag in the waveform window
to display waveform at steady state
 Ctrl+Left-Click on the Power Dissipation
Trace Label in the waveform view
 Waveform summary window will appear which
shows power dissipation in the IC
Example:
Measure the power dissipation in the
LTC3412A IC
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LTC3412A_DC_Load.asc
©2022 Analog Devices, Inc. All rights reserved.
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Simulating a
Transient Response
Demonstration
LTspice
Free – Fast – Unlimited
©2022 Analog Devices, Inc. All rights reserved.
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Current Load and Pulse Function
► You
can simulate a load with a Resistor or Current (active) load
► In
particular, the Pulse function with a current load is helpful for transient response
analysis
 Steps a current load from one load value to another load value
LTC3412APulseLoadSolution.asc
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©2022 Analog Devices, Inc. All rights reserved.
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4/20/2022
Edit the Current Load to a Pulse Function
► Edit
the .tran directive in the LTC3412A simulation to disable steady state detection
► Right-Click
on the current load
 Select “Pulse”
 Modify the attributes (see below). Click “OK”
*
65
Forces current
to be zero when
voltage is zero
©2022 Analog Devices, Inc. All rights reserved.
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Run the Simulation for Transient Response
► Run
the simulation
► Click on the OUT node to
display Vout
► Click on the output current load
to display Iout
► Notice the presence of the
pulse load
► Use the application of the pulse
load / transient response to
verify stability and modify the
compensation components, as
necessary.
LTC3412APulseLoadSolution.asc
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©2022 Analog Devices, Inc. All rights reserved.
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Homework
LTspice
Free – Fast – Unlimited
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©2022 Analog Devices, Inc. All rights reserved.
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Homework
► Design
and draft a circuit to measure the common mode rejection ratio (CMRR) of
the LTC1150 in LTspice
 LTC1150 is a ±15V Zero-Drift Operational Amplifier with Internal Capacitors
► Measure
and calculate the CMRR in dB using:
1. Nominal “ideal” resistor values
2. Randomly vary individual resistor values by 1% tolerance
► Explain
► Email
why there is a difference in CMRR measurement
your schematic file, results and questions in the next 2 days
 Mario.Gonzalez@arrow.com
 Charly.El-khoury@analog.com
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Resources and
Support
LTspice
Free – Fast – Unlimited
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©2022 Analog Devices, Inc. All rights reserved.
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LTspice Help File (F1) and Independent LTwiki.org
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©2022 Analog Devices, Inc. All rights reserved.
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EngineerZone LTspice Forum and Independent User Group
groups.io/g/LTspice
https://ez.analog.com/
Great for LTspice or ADI Model Support
(ideal for beginners)
Great community of analog engineers
(*not* ideal for beginners)
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©2022 Analog Devices, Inc. All rights reserved.
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Shortcut Keys Flyer, Getting Started Guide, Tutorials &
Technical Articles
www.analog.com/LTspice
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©2022 Analog Devices, Inc. All rights reserved.
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LTspice Examples and Demo Circuits
www.analog.com/LTspice
©2022 Analog Devices, Inc. All rights reserved.
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LTspice Technical Support on Software Bugs and ADI Models
► LTspice@analog.com
 Please provide the following details and attach your LTspice schematic file (.asc), project file (.plt),
and any non-standard model and symbol files (.asy, .lib, .txt, etc.)






Full Name:
Organization:
Phone Number:
Application:
Primary ADI Part(s):
Detailed Description:
If you have an issue with a third-party model,
please contact that vendor for support!
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©2022 Analog Devices, Inc. All rights reserved.
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4/20/2022
Happy Simulations!
MARIO.GONZALEZ@ARROW.COM
CHARLY.EL-KHOURY@ANALOG.COM
LTspice
Free – Fast – Unlimited
©2022 Analog Devices, Inc. All rights reserved.
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