WITH 0.5% REGULATION ACCURACY, NATIONAL SEMICONDUCTOR?S NEWEST LITHIUM-ION BATTERY CHARGE CONTROLLER OPTIMIZES PERFORMANCE OF SINGLE CELLS IN WIRELESS AND PC-BASED PRODUCTS

May 6, 1998 – National Semiconductor Corporation® today introduced the LM3621, a highly integrated, full-function offline controller for charge and end-of-charge control of a single-cell rechargeable Lithium-ion battery. Rated at 0.5% regulation accuracy, the device is capable of safely providing maximum battery capacity without the need for external precision resistors. The LM3621 is designed to control an isolated offline charger (flyback), DC-DC switching charger (buck) or linear charger.

"Lithium-ion batteries require more sophisticated charging and protection algorithms than nickel-based chemistry," said Venkatesh Shan, National?s director of marketing for power management products. "Battery performance can be significantly improved by taking advantage of the LM3621?s high accuracy, resulting in extended talk and standby times for cellular phones, and other one cell Lithium-ion battery-operated products. The LM3621 is simply the most comprehensive, full-featured single-cell lithium charger IC available in the market today."

The LM3621 controls five charge modes - conditioning, fast, top off, monitor and maintenance to ensure the cell is charged to 100% of its rated capacity. In the monitor mode or when AC power is removed from the charger, only one microamp current drain is placed on the battery. In addition, the LM3621 detects and flags defective cells, as well as over/under current and over/under voltage fault events to assure safe and reliable cell charges.

Several key features of the LM3621 include:

• Pin selectable 4.2V or 4.1V charge termination voltage for coke or graphite anode chemistries


• Charge current level regulation and current level detection with optional user override adjustment


• An internal 1-hour timer for 100% charge capacity


• Numerous fault detection flags for a high level of safety


• Two LED drivers for a visual indication of battery charge status

The device?s architecture is based on high-gain constant voltage, constant current (CVCC) control loops, which are well suited to pole splitting lead-lag compensation techniques. Internal circuitry includes a precision bandgap reference, an internally compensated op amp, voltage setting resistors and an NPN output driver for feedback control. The IC uses an onboard EEPROM to provide the flexibility necessary to accommodate customer-specific charge requirements.

Price and Availability
The LM3621M is currently available in a 16-pin SOIC package and is priced at $1.55 each when purchased in 1,000-unit lots.

For more information on the LM3621, visit our website at http://www.national.com/pf/LM/LM3621.html 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 www.national.com.

Editors? Note: Lithium-ion batteries are growing in popularity as an alternative to NiCd and NiMH batteries, especially for hand-held 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.