SIMPLIS Parts

SIMPLIS Zener Model

Any SPICE zener model installed in the SIMetrix library can be converted for use in SIMPLIS. When a zener is placed on a SIMPLIS schematic, a model parameter extraction routine is invoked to automatically convert the SPICE model to a SIMPLIS model. During the model parameter extraction process, SIMetrix/SIMPLIS automatically runs several SPICE simulations on the SPICE model and extracts the SIMPLIS model parameters. After the Piecewise Linear (PWL) model parameters have been extracted, the resulting zener model will run in SIMPLIS.

The extracted zener model can then be used to create a model for one of two zener configurations:

These zener configurations are more than a convenience, SIMPLIS will run faster with these models, and run into less problems with errors.

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Extracting the Zener Parameters

When you place a Zener symbol on a schematic, the Extract Zener Parameters dialog opens for you to edit the default test conditions. The default test conditions are defined using the command shell menu File ▶ Options ▶ SIMPLIS Options.... For additional information, see SIMPLIS Zener Options.

The following table describes the Extract Zener Parameters dialog test conditions.

SIMPLIS Zener Model

SIMPLIS extracts a model based on the parameters in the Extract Zener Parameters dialog. Although the zener model is internally saved as ASCII text, the following illustration shows the model in a schematic form.

Below is a schematic view of the zener model:

The Zener models this circuit element	Schematic
!R_D_POWER: Zener modeled by PWL Resistor

User-defined Models

The user-defined model uses parameters entered directly in the Edit Zener Parameters dialog without invoking the model extraction algorithms. A Zener can be switched from an extracted model to a user-defined model at any point; however the extracted parameters are by default copied over to the user-defined parameters, replacing any user-entered values. You can disable this behavior in the SIMPLIS Options by clearing the check box labeled Automatically copy extracted parameters to User-defined parameter. You can access these options from the command shell menu File ▶ Options ▶ SIMPLIS Options.... For more information, see SIMPLIS Zener Options.

User-defined model

Models these circuit elements	User-defined Schematic
!R_D_POWER: Zener modeled by PWL Resistor

Manually Generate and Customize Zener Models

You can customize or manually generate your own zener models using a parameter string with multiple PARAM_NAME=PARAM_VALUE key-value pairs. The parameter names and their functions are described in the Zener Model Parameters section below. You can interpret the SIMPLIS parameter values from device datasheet specifications and curves.

You can compose the parameter string in a text editor, spreadsheet, or script. The order of the parameter names in the parameter string and the capitalization of the parameter names are irrelevant.

You can include a PROTECTED=1 key-value pair to prevent from extracting a model and overwriting your manually generated parameters. The PROTECTED=1 key-value pair is not used in the simulation.  

Note: When you click on the device after adding the PROTECTED=1 key-value pair, the following message box appears to warn you that this is a hand-edited model.

To customize or generate your own zener model, follow these steps:

1. Create a parameter string of multiple PARAM_NAME=PARAM_VALUE key-value pairs using your preferred text editor, spreadsheet or script.
2. Add the PROTECTED=1 key-value pair to the parameter string.
3. Extract a zener model and place it on a schematic.
4. Right click on the symbol and select Edit/Add Properties....
5. Double click on the PARAM_VALUES property.
   The Edit Property dialog opens. At this point, you can change individual parameters in the Value box, or replace the entire default properties with the parameter string that you created in Step 2.
6. To replace the entire string, follow these steps:
   1. Click in the Value box and type Ctrl A to select all of the existing parameter string, and press Delete.
   2. Copy the parameter string you completed in Step 2 and paste into the Value box.
   3. Click Ok.
7. To change the name of your customized model, double click the VALUE property in the Edit Properties dialog, and change the name in the Value box.
8. To return to the schematic, click Ok.

Zener Model Parameters

The following tables detail the parameters which define the electrical behavior of the Zener model. Several other parameters in the PARAM_VALUES property have no effect on the electrical behavior of the model. These parameters are used to populate the Extract Zener Parameters dialog box.

Note: The default values are unlikely to appear in an extracted model. If these parameter values appear in your design, there has been an error in composing the parameter string.

Conduction Model

Zeners are modeled in SIMPLIS with Piecewise Linear (PWL) resistors. The PWL segments are represented by X,Y points

• The points are defined with the voltage on the X-axis and  the current on the Y-axis.
• The resistance is the inverse of the slope of any segment.
• The subscripts on IDx and VDx indicate the point pair location from lowest voltage, i.e.  reverse biased, to highest voltage, i.e. forward conduction.

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