ST ST7260E2, User Manual

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UM0497 Getting started
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This LED glows HIGH whenever the supply current increases from 500 mA. In the
evaluation board, the current limiter is used only to show the status of whether the current
limit is crossed or not, but it is not used to cut off the power supply.
1.2.3 Precision supply for the charger
Figure 2 shows circuit for the precision supply for the charger system. Here TL1431AI,
which provides 0.25% accurate reference voltage, is used to generate a precise voltage
supply for the charger system.
Figure 2. Reference voltage generation for the charger
With the help of this precision supply, we can easily achieve the 1% accuracy target which is
mandatory for Li-Ion charger systems.
1.2.4 Preferential power selector circuit
Figure 3 shows a preferential power selector circuit which is used to select the source power
supply for the USB controller.
Figure 3. Power selector circuit
This selector circuit works as follows. Whenever the USB supply (VBUS) is available, it is
used as the source supply. Battery power is only used when the USB supply is not available.