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USB/ac battery charger for portable devices

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article image Charges and maintains a Li-Ion or Li-Polymer battery, drawing power from either a USB or an ac wall adapter.

NATIONAL Semiconductor, represented in Australia by Arrow Electronics , has released a single-chip, dual-input USB/ac battery charger and power management integrated circuit (IC) that safely charges and maintains single-cell lithium-ion (Li-Ion) and lithium-polymer(Li-Polymer) batteries.

The LM3658 has a termination accuracy of 1.5%, extending battery life and making it suitable for portable devices including personal digital assistants, MP3 players, digital still cameras, internet appliances, instrumentation and smart phones.

It charges and maintains a Li-Ion or Li-Polymer battery, drawing power from either a USB or an ac wall adapter and defaulting automatically to the ac wall adapter setting when both power sources are present. It requires few external components and has integrated PowerFETs, a current sensor, reverse-blocking protection and thermal regulation for advanced battery protection.

Safety features include LED status indicators, safety timers and continuous temperature monitoring of the battery. The battery charger IC is packaged in a thermally enhanced 10-lead LLP package that measures 3mm x 3mm.

Programmed through an external resistor, the LM3658 allows charge currents from 50mA to 1000mA when operating from an ac wall adapter. When the battery is charged using USB power, charge currents of 100mA or 500mA are pin-selectable. The termination voltage is controlled to within 1.5% of 4.2V. With an input voltage range of 2.5V to 6V, the LM3658 supports a maximum output current of 1A, and can be adjusted through an external resistor. The internal power FETs are thermally regulated to obtain the most efficient charging rate for a given ambient temperature.

The device operates in five modes, including pre-qualification mode, constant-current mode, constant-voltage mode, top-off mode and maintenance mode. Optimal battery management is obtained through thermal regulation, battery temperature measurement and multiple safety timers. The LM3658 provides two open-drain outputs for LED status indication or connection to general-purpose onput/outputs (GPIOs).

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