TITLE	SIMetrix/SIMPLIS DVM Tutorial
APPLIES TO	SIMetrix/SIMPLIS DVM v6.10
KEYWORDS	dvm, tutorial, getting started, ltc3406b
DESCRIPTION	Tutorial for the SIMetrix/SIMPLIS Design Verification Module using the LTC3406B as an example.

• Intro to DVM
  
  • Supported Operations
  • Design Session Flow
  • Documentation Links
• Getting Started
  
  • Placing Basic Control
  • Creating Basic Testplan
  • Running Basic Testplan
  • Adding to the Output Report
• Intermediate Topics
  
  • Adding Input Source
  • Adding Output Load
  • Adding Bode Plot to the Output Report
• Full PowerAssist
  
  • Adding Three Terminal Output Load
  • Adding Full Power Assist Control
  • Managing Sources And Loads
  • Setting Control Parameters
  • Selecting Built-In Testplan
  • Viewing Output Report
• Miscellaneous Topics
  
  • Pre-Process Scripts
  • Post-Process Scripts
  • User-Defined Scalar and Spec Values

Intro to DVM

The SIMetrix/SIMPLIS Design Verification Module (DVM) provides the ability to run multiple user-defined simulation tests, aggregate the results and generate a simulation report, all without user intervention. DVM supports user-defined testplans allowing for the configuration of the simulation engine, analysis directives, temperature (where applicable), component values and test conditions. A properly configured schematic can also take advantage of DVM's new sensitivity and worst case analysis functions.

Supported Operations

The SIMetrix/SIMPLIS DVM testplan allows a user to specify the following on a test by test basis:

• Simulation Engine (DVM supports both SIMetrix and SIMPLIS)
• Analysis Statements (.AC, .TRAN, .POP, .DC, etc...)
• Include Files
• Pre- and Post-process Scripts
• Changes to Component Properties
• .VAR, .PARAM and .GLOBALVAR Statements for Circuit Parametrization
• Temperature (SIMetrix Only)

Design Session Flow

1. Working Schematic - DVM merely automates changes to the schematic and the execution of tests. If the schematic doesn't simulate, or if the design does not work properly, DVM may not help as it cannot debug design problems or modeling mistakes.
2. DVM Symbols - A DVM Control symbol must be placed on the schematic in order for the circuit to support DVM automation. The easiest way to get started is by using the "Basic" control. To use the built-in testplans or some specific advanced features, the "Full PowerAssist" control symbol and at least one managed DVM Source and one managed DVM Load are required.
3. DVM Testplan - A DVM Testplan is essentially a list of test definitions contained in a tab-separated text file. Each non-blank, non-comment line in the file is interpreted and executed.
4. Test Selection - A DVM Testplan can contain hundreds of tests; depending on the situation, it may not be desirable to run all of them at once. The DVM Test Selection Dialog allows the user to run any subset of the testplan.
5. Test Report - After execution of the testplan, DVM automatically generates an overview report showing the status of all the tests and linking to the individual test reports.

Documentation Links

The following links may be useful for further reading during or after the tutorial.

• testplan syntax documentation
• symbol documentation

Getting Started

This tutorial will use the LTC3406B Synchronous Rectified Buck schematic to demonstrate the features and operation of the SIMetrix/SIMPLIS Design Verification Module. This model was developed in-house solely from publicly available information found in the product's datasheet. The schematic can be found in the zip file distributed with this tutorial (download).

Starting Schematic

To start with, use SIMetrix/SIMPLIS DVM v6.1b or later to open the following schematic from the tutorial zip file.

LTC3406B/Test Ckts/LTC3406B - AC-Bode Plot.sxsch

The LTC3406B is a Sync Buck circuit and this schematic is configured to execute an Ac Analysis and generate a bode plot.

Placing Basic Control

To prepare a schematic for DVM, place a Basic DVM Control symbol on the schematic.

After placing the symbol, double click on it to edit its values. At the minimum, you should set the value for "Circuit Name" and "Description".

Creating Basic Testplan

Next, create a simple testplan file to use with the example circuit. To start with, use a header row with one analysis column to run the three basic tests, AC, Transient and POP. The testplan syntax documentation is available online and the example testplan below is included in the tutorial zip file.

support/testplan/basic.testplan

An easy way to grab the required analysis statements is to copy or cut the .AC, .TRAN and .POP directives from the F11 window.

Using the \n character sequence to indicate a line break allows for the inclusion of the .POP directive with the AC and Transient analyses. Should any analysis-specific .OPTIONS statements be required, use the same mechanism to include them.

Running Basic Testplan

To run a testplan, select DVM > Run > Choose Testplan... from the menu.

The DVM Test Selection dialog allows the user to select any subset of tests to be run. The options that appear in the dialog are dependent on the label entry for that row in the testplan. Tests without a label are automatically, if not creatively named.

After selecting tests for execution, DVM automates the circuit and analysis configuration and then launches the simulation engine, SIMPLIS in this case. Once the simulations are completed, the user is presented with the DVM overview report. Navigate to the test report for Test 1.

Adding to the Output Report

By default, the test report does not contain much more than a few links to the saved results files. Any waveform whose name starts with "DVM" or "DVM " will be featured in the test report. To demonstrate a featured waveform, rename the existing VOUT fixed voltage probe to "DVM VOUT". For convenience, enable the "Use separate graph" option and assign the probe to the "OUTPUT" graph.

Add another fixed voltage probe (Place > Probe > Voltage Probe) to the positive terminal of V2. Name it "DVM VIN" and assign it to the "INPUT" graph.

A convenient way to rerun a subset of tests is DVM > Run > Run Last Selected Tests.

After the simulations complete, navigate again to the test report for Test 1. Notice that graphics and statistics have been created for the two featured waveforms VIN and VOUT.

Schematic Configured for Basic DVM

At this point, the schematic is properly configured for basic DVM use. An already configured version of this schematic can be found in the tutorial zip file.

LTC3406B/Test Ckts/LTC3406B - DVM BASIC.sxsch

Intermediate Topics

More complicated tests can be constructed using additional DVM symbols, the DVM Input Source and DVM Output Load.

Adding Input Source

Remove the DC voltage source V2 and replace it with a DVM Input Source (DVM > Place > Source > Input Source).

Adding Output Load

Now remove the resistor R1 and replace it with a 2-Terminal Output Load (DVM > Place > Load > 2-Terminal Output Load).

DVM Sources and Loads include voltage and current probes, so remove the existing DVM VIN and DVM VOUT voltage probes. The Source Name and Load Name properties determine the names of the built-in probes. Change the Load Name property of the DVM Load I1.

Change the Source Name property of the DVM Source V2.

Adding Bode Plot to the Output Report

To include the Bode Plot in the output report for the Ac Analysis, change the two curve labels to start with "DVM".

Now, add to the testplan. Use the same analysis column and the same three basic tests, but add additional columns to configure source, load and label. Again, the example testplan below is included in the tutorial zip file.

support/testplan/intermediate.testplan

The source and load columns allow specification of the subcircuit that will be used for their respective symbols for that simulation. For the first test, V2 is configured to be a 4.5V DC voltage source, I1 is configured as a 2.0066 Ohm resistive load. For the second test, V2 is configured to be a 5.5V DC voltage source, I1 is configured as a 500mA DC current source. For the final test, V2 is configured to be a 5V DC voltage source, I1 is configured as a 1.0033 Ohm resistive load. See the testplan syntax documentation for more details on the acceptable values for the usage with DVM sources and loads.

The label is a | separated string that determines how a test is named in the test report and how it appears in the test selection GUI. Tests are grouped together and sorted alphabetically by label in the test selection GUI, however the order of execution is determined by its position in the testplan file.

Note the order in the GUI...

...compared to the order in the overview report

Examining the test report for the Ac Analysis, note that the Bode Plot is now a featured set of waveforms (order of the graphics varies, it might be necessary to scroll down in the report to locate the image)

Schematic Configured for Intermediate DVM

At this point, the schematic is properly configured for intermediate DVM use. An already configured version of this schematic can be found in the tutorial zip file.

LTC3406B/Test Ckts/LTC3406B - DVM INTERMEDIATE.sxsch

Full PowerAssist

DVM ships with several built-in testplans, including one specifically tailored for the Synchronous Rectified Buck topology. The built-in DVM testplans all require the circuit to be setup for Full PowerAssist with managed sources and loads. Though not strictly necessary, the schematic looks much better when the Bode Plot probe and the AC voltage source are removed.

Adding Three Terminal Output Load

When using a 3- or 4- terminal DVM Output Load, the probe and AC source can be automatically inserted into the subcircuit definition. In most cases, it is better to use the 4-terminal load as it makes fewer assumptions about the circuit, however the LTC3406B example circuit works fine with the 3-terminal load.

Remove the existing DVM 2-Terminal Output Load, the Bode Plot probe, the AC source and the connectors used to measure the Bode Plot. Place a DVM 3-Terminal Output Load (DVM > Place > Load > 3-Terminal Output Load) and connect it to the appropriate node to break the loop.

Adding Full Power Assist Control

Delete the existing DVM Basic Control and replace it with a new DVM Control that supports Full PowerAssist (DVM > Place > Control > Full PowerAssist).

managing sources and loads

To configure the DVM Control to manage the schematic's DVM sources and loads, right-click on the DVM Control and choose "Edit Additional Parameters".

Choose "Configure Sources and Loads" and hit OK.

Make certain the DVM Input Source (V2) is in the list of Managed Sources.

Make certain the DVM Output Load (I1) is in the list of Managed Loads.

Setting Control Parameters

The DVM Control should then configure itself as having one input and one output. The default values for many parameters can be used for this circuit, but some of the basic values must be customized for proper operation. Double click on the DVM Control and set the values for Circuit Name, Circuit Description and Switching Frequency under the General tab.

Under the Input tab, set the values for Nominal, Minimum and Maximum Input Voltage.

Under the Output tab, set the values for Nominal Output Voltage, Maximum Output Current as well as the values for Light Load @ Input1 Min and Max.

Under the Analysis tab, check the POP tab to be certain that the POP trigger information was correctly detected when the DVM Control was placed on the schematic.

Selecting Built-In Testplan

Once the control is configured, the schematic is ready to be run through its paces. From the built-in testplans menu, select the Sync Buck testplan (DVM > Built-In Testplans > Sync Buck (1 Input, 1 Output)).

Select a few tests to run.

Viewing Output Report

DVM will now run the tests, collect the results and compare the simulation data to the specifications entered in the DVM Control. If the same tests were selected as in the example, the overview report should show a test failure.

In this case, the test that failed was a light load test, and the test report shows that the simulated phase margin was insufficient compared to the specification.

Schematic Configured for Full PowerAssist

At this point, the schematic is properly configured for DVM Full PowerAssist. An already configured version of this schematic can be found in the tutorial zip file.

LTC3406B/Test Ckts/LTC3406B - DVM ADVANCED.sxsch

Miscellaneous Topics

SIMetrix/SIMPLIS ships with a powerful scripting language (script documentation). DVM allows for users to specify pre- and post-processing scripts to be run with a test. Pre- and post-processing scripts can be assigned either in a testplan (testplan syntax documentation) or through the DVM Control (supported by both the Basic and Full PowerAssist symbols). Pre- and post-process scripts are launched with the /quiet and /noerr flags to prevent script errors from halting DVM execution.

Pre-Process Scripts

Pre-process scripts are executed immediately before the simulation is launched. If multiple scripts are assigned, the order of their execution is as follows:

1. scripts assigned in the testplan, from left to right within the test definition row
2. scripts assigned in the control symbol

Pre-process scripts should start with the following Arguments definition.

Arguments @retval label report_dir log_file controlhandle

retval is the return value for the script. The return value is logged in the test log file.

label is the label of the currently executing test.

report_dir is the base directory for simulation results.

log_file is the location of the overview log.

controlhandle is the value of the Handle property for the DVM Control Symbol on the top level schematic.

Post-Process Scripts

Post-process scripts are executed after the simulation is completed and before any waveform processing is done. If multiple scripts are assigned, the order of their execution is as follows:

1. scripts assigned in the control symbol
2. scripts assigned in the testplan, from left to right within the test definition row

Post-process scripts should start with the following Arguments definition.

Arguments @retval label report_dir log_file controlhandle

retval is the return value for the script. The return value is a string vector containing the user-defined spec and scalar values generated by the post-process script.

label is the label of the currently executing test.

report_dir is the base directory for simulation results.

log_file is the location of the overview log.

controlhandle is the value of the Handle property for the DVM Control Symbol on the top level schematic.

User-Defined Scalar and Spec Values

The format for the retval string vector to return user-defined scalar and spec values is as follows:

[ 'scalar1=value1~scalar2=value2', 'spec1=status,value1~spec2=status,value2' ]

For spec values, status should be either pass, warn or fail.

A simple example that shows two scalar values and a single spec:

The resulting test report should look something like the following: