ST AN2726 Application note
STw4102 single Li-Ion cell battery charger including gas gauge
1 Introduction
This application note describes the STEVAL-ISB006V1, an evaluation board specifically
designed for the STw4102 battery management integrated circuit.
This document provides:
● a brief description of the STw4102
● a description of the evaluation board
● a detailed bill of materials of the evaluation board
● the layout of the evaluation board.
Figure 1. STw4102 evaluation board
AN2726
Application note
Evaluation board user guidelines for the
July 2008 Rev 1 1/10
www.st.com
About the STw4102 AN2726
2 About the STw4102
The STw4102 is a standalone constant-current, constant-voltage (CCCV) linear charger
dedicated to Li-Ion batteries. The device has a dual charging capability that uses the main
input adaptor (wall or car adapter) or a USB cable with no external component.
The STw4102 offers a programmable fast-charge current using an external resistor. The
thermal regulation circuitry limits the charge current so that the die junction temperature
never exceeds the maximum specified value. An end-of-charge output pin indicates the
charge termination when the fast charge current drops below 10% of the programmed
current value.The STw4102 contains an accurate gas-gauge based on a 13-bit AD
converter. An external resistor is used between the battery and ground pin to sense a
charge/discharge current. With a typical 30 mΩ resistor, the current can be up to 2.5 A and
the 24-bit accumulator system provides a capacity of up to 914 mA.h.
The STw4102 has the following key features.
■ Constant-current constant-voltage (CCCV) linear charger.
■ Common or separate USB/wall adapter inputs.
■ Fast-charge current control up to 1 A for wall adapters and up to 500 mA for USB.
■ Support for currents higher than 1 A using external components.
■ Programmable charge voltage (4.1 V, 4.2 V, 4.3 V, 4.35 V) with 1% accuracy.
■ Thermal regulation.
■ Trickle-charge mode at low battery voltage.
■ Wall adapter voltage up to 13 V.
■ Battery over-voltage protection at 4.7 V.
■ Gas gauge with 13-bit AD converter.
■ Battery voltage monitor with 7- to 12-bit AD converter.
■ I²C interface for device monitoring and control.
■ Charge status output pin.
■ Power detection output pin.
■ Programmable watchdog security timer.
■ 4.7 V LDO regulator (with external power MOSFET).
Figure 2 describes the application schematics, with the typical connections and peripheral
components surrounding the charger IC.
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AN2726 About the STw4102
Figure 2. Typical application for the STw4102
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Refer to the datasheet for more detailed information on the STw4102.
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