SIMPLIS Tutorial / 2.0 Entering the Design |

This section of the tutorial explains how to edit multi-level models. You will start with the schematic that you saved in 2.2 Edit Standard Component Values and then change more component values for this design.

In this topic:

This topic addresses the following key concepts:

- Inductors and Capacitors used in SIMPLIS can have multiple model levels. A model level represents the modeling complexity of the device; for example, a single capacitor symbol can model an ideal capacitor or represent a more complex model such as a capacitor with ESR and ESL.
- The multi-level lossy inductor model has a built-in high frequency limit. At frequencies above the corner frequency, the inductor becomes resistive.

In this topic, you will learn the following:

- How to edit symbols and change values on multi-level models.
- How to change the model level.

Both the capacitor and inductor in this design are multi-level models, where the model level determines the parasitic elements included in the model. Four model levels, 0 through 3, exist for the capacitor.

- A level 0 capacitor is ideal and no ESR, ESL or leakage is modeled.
- As the level number increases, parasitic elements are added to the model.
- To learn more about the four model levels, click the
**Help**button on the editing dialog to open the topic for the capacitor model.

This design is already set to a level 1 model. To change the output capacitor value, follow these steps:

- Double click the
**C1**symbol.**Result:**The Edit Multi-Level Capacitor dialog opens. - Change the
**Capacitance**value to**220u**as shown below. - Click
**Ok**.

The inductor used in this design is also a multi-level model. The inductor has two model levels:

- Level 0 represents a pure inductor.
- Level 1 adds an equivalent series resistance (ESR).

Both inductor model levels have a parallel shunt resistance that limits the high-frequency response of the inductor. This is important for reasons that will become apparent later in the tutorial; for now, however, remember that the inductor has a built-in upper frequency limit and, at frequencies above this limit, the inductor becomes a resistor, reflecting the real behavior of the inductor.

To automatically calculate the shunt
resistance value from the corner frequency, click on the **Calc...** button in the
editing dialog.

The inductance value for this design is 680nH. To change the inductor value, follow these steps:

- Double click the
**L1**symbol.**Result:**The Edit Multi-Level Lossy Inductor dialog opens. - Change the
**Inductor**value to**680n**as shown below. - Next you will change the inductor
**Shunt resistance**parameter. To change the shunt resistance, follow these steps:- Click on the
**Calc...**button.**Result:**The Calculate New Shunt Resistance dialog opens with the 680nH inductance value copied from the main dialog into the Calculate New Shunt Resistance dialog. The dialog has a built-in calculator function which calculates the new shunt resistance value based on the inductance and the desired frequency. You can change the**Frequency**entry and see the**Shunt Resistance**value change. - The default frequency value of 10GHz is suitable for almost all switching power
applications. This is the frequency above which the inductor will become resistive.
Click
**Ok**on the Calculate New Shunt Resistance dialog to save the value to the Edit Multi-Level Lossy Inductor dialog.**Result:**The calculated shunt resistance value of 42.7257kΩ is returned to the Edit Multi-Level Lossy Inductor dialog.

- Click on the
- Click
**Ok**.

To save your schematic, follow these steps:

- Select .
- Navigate to your working directory where you are saving your schematics.
- Save the file as
**2_my_buck_converter.sxsch**. - When prompted to overwrite the existing file, click
**Yes**.Note: You will use this schematic in the next section, 2.4 Edit Parameter-Extracted Models.