AN1464 Datasheet, PDF (1/27 Pages) STMicroelectronics – LOW-COST DOUBLE LI-ION BATTERY CHARGER

AN1464
APPLICATION NOTE
LOW-COST DOUBLE LI-ION BATTERY CHARGER
USING ST6255C/ST6265C MCU
by Microcontroller Division Applications
DESCRIPTION
In everyday life, more and more portable electronic appliances, such as mobile phones, are
powered by rechargeable batteries with a requirement for high capacity, small size and low
weight. Li-ion batteries have been widely used to support these kind of devices due to their su-
perior capacity for a given size and weight.
This Application Note explains how to use the ST6255C 8-bit Microcontroller in a cost-effec-
tive battery charger for Li-ion batteries, as implemented in the Li-ion Battery Charger Demon-
stration Board. The design implemented on this Board is easily scaleable to other types of Li-
ion batteries simply by changing the software parameters and primary input voltage/current.
The charger has two slots. The front one can be used to plug in a simple battery or a mobile
phone with an internal battery. The rear slot is for pluging in a stand-alone battery. A pair of
LEDs (green/red) are assigned to each slot to indicate the charge status.
The main target MCU is the ST6255C. Among other features, this microcontroller embeds an
A/D converter, a PWM signal generator and 4K bytes of program memory, which is enough to
embed the algorithm. The board also supports the ST6265C MCU, which adds 128 bytes of
internal EEPROM to the features of the ST6255C.
The evaluation board is intended to be equipped with two mobile phone batteries and an
ST62T55C OTP sample to execute the demonstration software. The software parameters are
adapted to a fixed battery capacity of 600 mAh. With minor modifications to the system, it is
possible to make the charger read the battery capacity and change its parameters accordingly
(feature not implemented on the evaluation board).
The board must be powered by an external low-voltage DC supply (6 V, 800 mA).
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