NATIONAL SEMICONDUCTOR ANNOUNCES COMPACT CHARGE CONTROLLER FOR SINGLE-CELL OR DUAL-CELL LITHIUM-ION BATTERY PACKS IN HANDHELD COMMUNICATIONS AND COMPUTING PRODUCTS
July 28, 1998 - National Semiconductor Corporation® today introduced a highly integrated, low-cost controller for charge and end-of-charge control of single-cell and dual-cell lithium-ion battery packs for handheld communications and computing products. The LM3620, rated at 1.2% regulation accuracy, precisely controls charge voltage from a current-limited DC-DC switching charger or linear charger. Housed in an SOT23-5 package, the part has the smallest application footprint of any device in its class. Moreover, National's safely provides maximum battery capacity without the need for external precision resistors.
"Designers are currently required to produce complex application circuits that perform the same task the LM3620 can do easily," said Venkatesh Shan, National's director of marketing for power management products. "With the LM3620, only four inexpensive external components are required to perform charge control functions, resulting in significant reductions in printed circuit board space and cost. To date, similar applications have required a dozen parts or more," he added.
In its simplest form, an application circuit using National's charge controller consists of a capacitor, diode, a transistor and a resistor. The external PNP or PMOS transistor, controlled by the LM3620, provides charge current to the battery from an external DC power source. When the power source is disconnected from the LM3620 controller, a switch opens in the LM3620, reducing current drain from the battery back into the LM3620 to 10 nA.
The LM3620 operates from a wide range of DC sources from 4 volts to 30 volts. In addition, the LM3620 offers pin-selectable charge termination voltages for either coke (4.2V) or graphite (4.1V) anode chemistry.
Internal circuitry of the LM3620 includes an operational transconductance amplifier, a bandgap voltage reference, a NPN driver transistor and precision voltage setting resistors. The output of the amplifier will drive an external power transistor if higher drive currents are required.
Price and Availability
The LM3620M is currently available in a SOT23-5 package and is priced at $0.75 each when purchased in 1,000-unit lots.
For more information on the LM3620, visit our website at http://www.national.com or contact National's Customer Response Group at 1-800-272-9959.
National Semiconductor Corporation produces system on-a-chip silicon solutions for the information highway, based on its leadership in analog and mixed signal technologies. National is headquartered in Santa Clara, California, and focuses on the communications, personal systems and consumer markets. National has annual sales of approximately $2.5 billion and 13,000 employees worldwide. Additional company and product information is available on the World Wide Web at http://www.national.com
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Editors' Note: Lithium-ion batteries are growing in popularity as an alternative to NiCd and NiMH batteries, especially for handheld and portable devices where size, weight and operating time are important considerations. Lithium-ion batteries have half the weight and occupy 70% of the volume of comparable NiCd and NiMH batteries. In addition, Lithium-ion batteries do not suffer from memory effect and are environmentally safe.
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