Introduction

Switch mode power supplies are more efficient at DC-DC conversion than typical linear voltage regulators but can often be overlooked because of the higher complexity and cost related to them. Dedicated controller ICs will typically only operate with predetermined voltage ranges and switching parameters, meaning that different designs have to be used in different use cases. Implementing the switching controller using the core independent peripherals of the AVR® DB family of microcontrollers makes for a highly flexible system, adding only passive components to the bill of materials, thereby reducing the number of more expensive ICs.

This application note shows how to implement a feedback switching controller for a buck converter using the core independent peripherals of the AVR DB family of devices. After the initial set-up, the core independent peripherals are independent of the CPU, allowing the microcontroller to do any other task in parallel.

In Closed Loop Voltage Control using Core Independent Peripherals, a short overview of the feedback controller is given, as well as how to implement it using the core independent peripherals. The general design of the buck converter is covered in Component Selection - Buck Converter. Setting the output voltage of the buck converter is covered in Setting Output Voltage, while Component Selection - Error Amplifier goes over the principles for PWM generation and design of the error amplifier compensation network. Finally, some measured characteristics of an example implementation are presented in Results.

This application note does not go into detail on aspects like efficiency and time variance in current and voltage or layout considerations. Other application notes, linked below, go into more detail and can be used in conjunction with this application note to provide a deeper understanding of the subject.

• AN968 - Simple Sychronous Buck Regulator
• CIP Hybrid Power Starter Kit User's Guide

The available schematics of the CIP Hybrid Power Starter Kit can be used as a reference for layout and component selection.