NATIONAL SEMICONDUCTOR ADAPTER INTERFACE CIRCUIT (AIC) IC OPTIMIZES SAFETY AND POWER CONTROL FUNCTIONS FOR NOTEBOOK COMPUTERS

August 28, 2000 - National Semiconductor Corporation (NYSE:NSM) today introduced the first single-chip Adapter Interface Circuit (AIC), a highly integrated LM2601 chip that identifies a notebook computer's power source and optimizes computer operation or battery charge cycles. The LM2601 AIC detects alternative power sources and - depending on the input voltage - triggers various power-saving and safety control features. Power sources include battery packs, constant-voltage output AC adapters, auto and airline adapters.

"With the increased use and greater mobility of notebook computers, more adapters are being made available to the business traveler," noted Venkatesh Shan, National's director of marketing for power products. "It follows that stronger emphasis will be given to safety precautions that guard against excessive power drain and hazardous battery conditions, particularly by the airlines."

The LM2601 replaces separate logic, comparator and reference ICs as well as several discrete components in the notebook computer's power circuit. Based on the input voltage from the battery or adapter, the IC sends power status to the notebook's microcontroller and drives MOSFET switches to electrically connect or disconnect the adapter. A low level of <12V indicates battery operation, and although the adapter is plugged in, the computer will continue to use the battery as its power source. A voltage level between 12V and 17V indicates presence of an external auto or airline adapter, ample for efficient operation, but insufficient voltage for battery charge. When the input is greater than 17V, the AIC keys the CPU to run the computer and simultaneously charge the battery.

Examples of the power management and control functions provided by the LM2601 AIC include:

• Rejects a battery charge cycle automatically when powered from an airline power adapter (<17V) for in-flight safety. 
• Prolongs battery life by passing unused power as a charge to the battery pack, even while drawing full-rated operational current from a constant-voltage adapter. 
• Detects positive current flow and closes FET when diode current exceeds 100mA. 
• Switches external FET on to completely discharge battery for calibration when plugged into an adapter, then subsequently facilitates complete battery recharge. 
• Minimizes battery drain by limiting leakage current when powered from an external power source. 
• Maintains operational state when battery is removed during calibration.

National's LM2601 works with any battery chemistry and operates from a wide input voltage range of 5V to 24V, making it compatible with virtually any notebook computer. A hysteresis of 2V for the adapter presence prevents oscillation during momentary voltage drops. Maximum current draw threshold can be programmed with a single external resistor.

Price and Availability
The LM2601MTC is currently available in a TSSOP-14 package and is priced at $1.50 each when purchased in 1,000-unit lots. For more information on the LM2601, visit National's World Wide Web site at http://www.national.com/pf/LM/LM2601.html.

About National Semiconductor
National Semiconductor provides system-on-a-chip solutions for the information age. Combining real-world analog and state-of the-art digital technology, the company's chips lead many sectors of the personal computer, communications, and consumer markets. With headquarters in Santa Clara, California, National reported sales of $2.1 billion for its last fiscal year and has about 10,500 employees worldwide. Additional company and product information is available on the World Wide Web at www.national.com.