Multiple-Battery Charger IC Tackles Larger Portable Products

Feb. 2, 2006
Larger portables need lots of power, and Maxim's MAX8730 is up to the job. This precision constant-current,-constant-voltage charger IC charges three or four lithium-ion cells in series at charge currents greater than 3.5 A. It also can charg

Larger portables need lots of power, and Maxim's MAX8730 is up to the job. This precision constant-current,-constant-voltage charger IC charges three or four lithium-ion cells in series at charge currents greater than 3.5 A. It also can charge nickel-metal-hydride and nickel-cadmium cells.

The device can be hardwired or controlled by a microprocessor to set the charging current or voltage. Battery-voltage regulation is accurate to 0.5%, which increases battery capacity and minimizes charging time. A hysteretic comparator detects the presence of an ac power adapter and automatically selects the appropriate power source.

The charge current and input current-sense amplifiers have low-input offset errors, allowing the use of small-value sense resistors. For light loads, the MAX8730 operates in discontinuous conduction mode for improved efficiency. At higher charging currents, this switches to continuous-conduction mode, with inductor current never crossing zero. Analog inputs control input current limit, charge current, and voltage.

The MAX8730's dc-dc converter drives a p-channel MOSFET and uses an external freewheeling Schottky diode. A fold-back feature reduces the Schottky requirement at low battery voltages. An integrated 3.3-V low-dropout can supply over 20 mA to external circuitry or ICs, such as a keyboard controller.

Packaged in a 5- by 5-mm, 28-pin QFN, the MAX8730 costs $5.04 in 1000-unit quantities.

Maxim Integrated Products
www.maxim-ic.com

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