Let's try using LTspice - Let's run multiple simulations automatically with a batch file!

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When using LTspice in practice, does the simulation time become abnormally long?

In such cases, you might think, "It would be easier if we could automatically run simulations of different circuits in the middle of the night."

This time, I will introduce a method to automatically run multiple circuit simulations using the command prompt as a method to eliminate such troubles.

If you are just starting LTspice, we recommend that you look at the "basics" from the list below.

Let's use LTspice series list is here

Also, if you would like to see a video on how to write a basic circuit and how to execute it, there is an on-demand seminar that does not require you to enter personal information, so please take a look if you are interested. Detailed information about the seminar is also provided to those who fill in the questionnaire.

LTspice On-Demand Seminar - Function check with RC circuit -

Precautions before execution

LTspice_Automatically run multiple simulations with batch files_Control Panel_Automatically delete .raw files — Figure 1: Automatically delete .raw files[*] in Control Panel

If you leave the data after running the simulation, the hard disk capacity will be squeezed, so I think that there are many cases where the result file is automatically deleted after the simulation is finished. If you run a simulation using the command prompt with that setting, all the simulation results will disappear.

Therefore, when executing the simulation using the method explained here, uncheck "Automatically delete .raw files[*]" in the control panel in order to keep the simulation results.

1. Using Command Prompt

Before creating a batch file and running multiple circuit simulations, let's make sure that we can run LTspice simulations from the command prompt.

Open a command prompt and cd C:\Program Files\LTC\LTspiceXVII to move to the directory "\Program Files\LTC\LTspiceXVII" where the LTSPICE exe file is located.

LTspice_batch file to automatically run multiple simulations_change to directory with executable file — Figure 2: Change to the directory with the LTspice executable

2. Netlist generation

Generate a netlist from a circuit file (.asc). A netlist is generated by executing XVIIx64.exe -netlist "file directory" on the command prompt (Figure 3). file directory specifies the folder that contains the circuit files to run.

This time, I will use the JIG file of the LDO product called LT1117 prepared by LTspice.

On the command prompt, specify C:\Users\username\Documents\LTspiceXVII\examples\jigs\1117.asc and execute. Then, a netlist will be generated in the same folder containing the schematic file (Fig. 4).

For how to use the files prepared in the JIG folder, please refer to the article "Easy! How to draw a circuit diagram in 5 steps".

LTspice_Run multiple simulations automatically with batch file_Generate netlist — Figure 3: Netlist generation

Confirm that a netlist called 1117.net is generated in the folder containing the circuit files (Figure 4).

LTspice_Run multiple simulations automatically with a batch file_Confirm netlist — Figure 4: Check netlist

3. Run the simulation

Now try running the simulation using the netlist (.net).

By executing XVIIx64.exe -b C:\Users\username\Documents\LTspiceXVII\examples\jigs\1117.net on the command prompt, the simulation result (waveform file) 1117.raw is generated.

LTspice_Running multiple simulations automatically with a batch file_Running simulations — Figure 5: Running the simulation

Waveform data called 1117.raw is output as follows.

LTspice_Automatic execution of multiple simulations with a batch file_Simulation results (waveform data file) — Figure 6: Simulation results (waveform data file)

4. Confirmation of simulation results (waveform)

Double-click the 1117.raw file to open it with LTspice.

Then select View →Visible Traces from the toolbar to open the Select Visible Waveforms menu.

LTspice_Automatic execution of multiple simulations with a batch file_How to display simulation results — Figure 7: How to display simulation results

In this window, select the node whose waveform you want to see. Figure 10 is the circuit diagram of the simulation we ran this time. I want to check the output waveform, so I check the number of the OUT node. . When I checked with the JIG circuit file, V(n002) corresponds.

Be careful because you can't know the number of the node of the OUT pin in advance.

It is convenient to label the nodes before running the simulation so that you can easily identify the node whose waveform you want to check.

(Reference) Let's use LTspice - clean circuit diagram with "Label Net"

LTspice_Batch file automatically runs multiple simulations_LT1117 schematic — Figure 8: LT1117 schematic

From the selection list in Figure 9, select V(n002) and load current (I1) that correspond to the OUT node.

LTspice_Batch file automatically executes multiple simulations_Waveform selection — Figure 9: Waveform selection

The resulting waveform looks like this (Figure 10). I(I1) is the load current change waveform, and V(n002) is the OUT waveform.

It can be confirmed that the output voltage VOUT fluctuates due to the fluctuation of the load current I1.

LTspice_Automatic execution of multiple simulations with a batch file_Simulation results — Figure 10: Simulation results

Batch processing

Processing 1 to 5 is the method of manually executing a simulation using commands on the command prompt.

By creating this command processing in text and making it a bat file, it is possible to automatically execute multiple simulations in succession. This is useful when processing multiple time-consuming simulations while you sleep.

As a reference, I made a sample file for batch processing JIG files of LT1117 and LT1118.

Download the sample file below and try it out.

The downloaded ZIP file contains a text file called LTspice.txt.

Change the "username" part of the directory in the text to the folder name on your PC.

If you want to run it, change the extension txt to bat and run it.

* When simulating for a long time, please note that the simulation will stop when the PC goes to sleep.

sample file

At the end

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