Rev. 0.1 7/06

Copyright © 2006 by Silicon Laboratories

AN294

AN294

1. Introduction

The Frequency Compensation Simulator (FCS) enables the user to easily design and optimize closed-loop

frequency compensation for buck converters based on the Silicon Labs Si8250 digital power controller. The FCS

simulates both the controller and power stages providing a single simulation of the entire system. The intuitive user

interface generates frequency response gain and phase graphs, and automatically generates filter coefficient

values for the Si8250 in both decimal and hex formats.

2. Features

System compensation design and optimization in a single intuitive simulation environment.

Directly generates compensation loop filter coefficients for the Si8250 digital controller.

Greatly reduces design and system verification time.

3. User Interface

The default FCS GUIs are shown in Figures 1 and 2. The Bode Plot GUI of Figure 1 illustrates the closed-loop

magnitude and phase response for the Si8250-based buck converter. This GUI displays the response plots with

loop bandwidth, and gain and phase margin data in real time, and includes a cursor function to facilitate plot

measurement at any point. The Real Time Compensation data entry GUI shown in Figure 2 consists of multiple

user interfaces, each with its own selection tab (the Setup GUI is shown). The user specifies power stage and

controller parameters using this set of GUIs. (For example: power stage parameters such as output filter L and C

values; Si8250 control parameters such as ADC LSB size and sampling frequency, PWM frequency, etc).

Figure 1. Default Bode Plot GUI

Relevant Devices

This application note applies to the Si8250/1/2 Digital Power Controller and Silicon Laboratories Single-phase POL

Reference Design.