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Charger IC keeps very close tabs

Posted: 12 Jul 2005 ?? ?Print Version ?Bookmark and Share

Keywords:national semiconductor? lm3658? battery charger ic? power management ic?

Touting high accuracy and advanced safety features, National Semiconductor Corp.'s LM3658 is a dual-input USB/AC battery charger and power management IC designed to keep close watch on single-cell lithium-ion/polymer batteries.

"Today's portable systems demand short charge times, accurate voltage termination and reliable battery supervisory functions," said Gianluca Colli, director of integrated system products for the Portable Power Products Group. "The LM3658 delivers high value to the system designer by offering a cost effective and versatile solution coupled with optimum performance in a tiny 3-by-3 mm package."

In basic operation, the chip steps through five operating modes: pre-qualification, constant-current, constant-voltage, top-off and maintenance. The LM3658 delivers a charge current from 50mA to 1A (programmed by a single resistor) when operating from an AC wall adapter. It delivers a pin-selectable 100mA or 500mA when the battery is charged from a USB source. The LM3658, working from a 2.5V to 6V input, defaults automatically to the AC wall adapter setting when both power sources are present.

The chip features high accuracy for the charge terminating voltagewithin 1.5 percent of 4.2Vto extend battery life, making it well suited for a variety of portable devices including personal digital assistants, MP3 players, digital still cameras, Internet appliances, instrumentation and smart phones. Advanced management circuitry keeps tabs on thermal regulation and battery temperature, and multiple safety timers minimize the chance for runaway conditions. The LM3658 provides two open-drain outputs for LED status indication or connection to general-purpose input/outputs (GPIOs).

The chip's product folder can be found at National's website. Already available, the LM3658, packaged in a thermally enhanced 10-lead LLP, is priced at $1.50 each in 1,000-unit quantities. An evaluation board and Pb-free package options are also available.

- Vincent Biancomano


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