National Semiconductor's New Family of High-Performance Controllers Meets a Wide Range of Power Supply Switching Regulator Requirements

Business Wire, Oct 2, 2000

Business Editors/Technology Writers

SANTA CLARA, Calif.--(BUSINESS WIRE)--Oct. 2, 2000

Addressing the need for greater flexibility in high-efficiency switching power supply design, National Semiconductor Corporation (NYSE:NSM) today introduced a trio of switching controllers for general-purpose power supplies. The LM3477, LM3478 and LM3488 are the first in a family of small, versatile, solutions with a wide range of input voltages, high operating frequencies and other advanced features. The broad applicability of National's new controller family justifies it as a multi-purpose standard that shortens the qualification process and results in a low-risk, reusable solution. Typical applications include custom power supplies in high-volume systems such as DSL and cable modems, set-top boxes, desktop and notebook PCs, distributed power systems, automotive information appliances and a variety of battery-powered portable products.

National's versatile controllers can be used in traditional switching regulator topologies such as buck, boost and flyback, as well as other topologies including CUK, inverting and SEPIC. Complemented with evaluation boards, a cookbook of common circuits, and WebSim(tm)

(simulation software), the new chips have the flexibility to satisfy most high-performance power supply requirements.

"National's versatile, 'use-anywhere' controllers provide the perfect balance of size, efficiency, current handling and cost," said John Perzow, National's manager of strategic marketing for switching regulator products. "They also open new possibilities for finely tuned application-specific power supply solutions, while retaining many of the ease-of-use features and all the reliability of National's proven Simple Switcher(tm) regulators. With design support tools like WebSim(tm) on National's WebBench(tm), a library of evaluation boards and our circuit solutions cookbook, designers can be assured of a fast, easy and complete application-specific regulator solution."

National's switching controllers feature a current-mode control scheme that provides superior bandwidth, excellent transient response and cycle by cycle current limiting over a wide input voltage range. Versatility is designed in through the combination of wide input voltage range, ceramic capacitor compatibility, programmable switching frequency and multiple protection modes.

The LM3477 controller is for topologies requiring high-side N-FETs, while the LM3478 and LM3488 controllers are suitable for regulator topologies requiring low-side N-FETs. The LM3488 can also be synchronized to an external clock, and includes a 1.5% internal reference (over temperature).

The input voltage range for the LM3478/88 boost controller is 2.95V to 40V and the switching frequency for both parts can be adjusted between 100kHZ and 1MHz with a single external resistor. The LM3477 step-down controller operates from 2.95V to 35V with a fixed clock frequency of 500kHz. Efficiencies up to 95% are achievable. Other features include load regulation of 0.5%, softstart and adjustable current limit.

A power-saving shutdown mode extends battery life by reducing quiescent current to 5 microamps (LM3477 and LM3488). Protection features include thermal shutdown, undervoltage and overvoltage protection, short-circuit protection, cycle-by-cycle current limit and adjustable current limit.

Price and Availability

The LM3477MM and LM3478MM controllers are currently available in National's 8-lead Mini-S08 (MSOP-8) package, and are priced at $1.65 each when purchased in quantities of 1000. The LM3488MM controller, with external synchronization, higher accuracy, and lower shutdown current, also in National's 8-lead Mini-SO8, is $1.95 in 1000s.

For more information on National's new versatile family of switching controllers, visit our website at www.national.com/appinfo/power/, or contact National's Design Support Group at 800/272-9959.

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.

Note to Editors: National Semiconductor is a registered trademark and WebSim, WebBench and Simple Switcher are trademarks of National Semiconductor.