Power Electronics

Li-ion Charger Packs Many Features in Tiny IC

National Semiconductor’s LM3658 is a dual-input USB/ac battery charger and power management integrated circuit (IC) that safely charges and maintains single-cell Li-ion/Li-polymer batteries. The battery charger IC is packaged in a small, thermally enhanced 10-lead LLP package that measures 3 mm × 3 mm. In addition, the LM3658 features a high termination accuracy of 1.5%.

The LM3658 charges and maintains a Li-ion 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. The LM3658 requires few external components and features integrated PowerFETs, a current sensor, reverse-blocking protection and thermal regulation for advanced battery protection. Advanced safety features include LED status indicators, safety timers and continuous temperature monitoring of the battery. The LM3658 allows charge currents from 50 mA to 1000 mA when operating from an ac wall adapter. When the battery is charged using USB power, charge currents of 100 mA or 500 mA are pin-selectable. The termination voltage is controlled to within 1.5% of 4.2 V. With an input voltage range of 2.5 V to 6 V, the LM3658 supports a maximum output current of 1 A, 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 prequalification 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). Unit pricing is $1.50 in 1000-unit quantities.

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