AN3531
Simple LiPo Battery Management
Introduction
Author: Keith Curtis, Microchip Technology Inc.
Given the ubiquitous nature of battery-powered systems, battery management has become a required feature on
most new designs. The purpose of battery management is threefold;
• Control of the battery charging
• Regulation of the battery output for use by the system circuitry
• Monitoring the charge input/output to approximate the amount of remaining charge
This application note will address all three areas; charging, load regulation and battery charge/health estimation. To
simplify the design, an ASIC charger and ASIC switching regulator will be used to do the actual charging and load
regulation in the design. Two high-side current mirrors will also be used to monitor both the battery charging and
battery load currents.
© 2020 Microchip Technology Inc.
Application Note
DS00003531A-page 1
Table of Contents
Introduction.....................................................................................................................................................1
1. Design Specifications..............................................................................................................................3
2. Hardware Theory of Operation................................................................................................................4
2.1. System Hardware Blocks............................................................................................................. 4
2.2. Load Voltage Regulator................................................................................................................4
2.3. Battery Charger............................................................................................................................ 5
2.4. Current Mirrors............................................................................................................................. 5
2.5. Temperature Sensors................................................................................................................... 5
2.6. Analog Inputs............................................................................................................................... 6
2.7. Digital Inputs.................................................................................................................................6
3. Software Theory of Operation................................................................................................................. 7
3.1. Idle State...................................................................................................................................... 7
3.2. Charge State................................................................................................................................ 7
3.3. System-On State.......................................................................................................................... 7
3.4. Error State.................................................................................................................................... 8
3.5. Coulomb Counting........................................................................................................................8
3.6. Interrupts...................................................................................................................................... 8
4. Conclusion.............................................................................................................................................. 9
4.1. Enhancements............................................................................................................................. 9
The Microchip Website.................................................................................................................................10
Product Change Notification Service............................................................................................................10
Customer Support........................................................................................................................................ 10
Microchip Devices Code Protection Feature................................................................................................ 10
Legal Notice................................................................................................................................................. 10
Trademarks...................................................................................................................................................11
Quality Management System....................................................................................................................... 11
Worldwide Sales and Service.......................................................................................................................12
AN3531
© 2020 Microchip Technology Inc.
Application Note
DS00003531A-page 2