Microchip Technology

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  • Intelligent Lithium Ion Battery Charger

  • Created: May 26, 2016

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Description

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Summary

This reference design is a simple intelligent battery charger, which can charge a single cell Li-on/Lipo (3.7V/4.1V) battery through a USB port. It uses MCP73831 linear charge management controller of Microchip that employs a constant-current and constant voltage charge algorithm with selectable preconditioning and charge termination. The MCP73831 device limits the charge current based on die temperature during high power or high ambient conditions. This thermal regulation optimizes the charge cycle time while maintaining device reliability.


In the circuit, LEDs indicate the charging status. The red LED indicates that it is still charging while green LED indicates that battery has been fully charged. The device has overcharging protection, which makes it safe for charging. The basic algorithm is to charge at constant current until the battery reaches 4.2Vpc (volts per cell), and hold the voltage at 4.2V until the charge current has dropped to 10% of the initial charge rate. The STAT pin is output for connection to an LED for charge status indication. Meanwhile, preconditioning, fast charge and termination currents are scaled by placing a resistor from PROG to VSS. The charge management controller can be disabled by allowing the PROG input to float.


This intelligent lithium ion battery charger is common in portable electronics. It can be very useful to charge batteries in mobile phones, digital cameras and clocks. This device can also be used to charge batteries for radio-controlled toys such as quadcopters and RC boats.