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National Semiconductor Introduces Industry’s First High-Power-Density, Self-Synchronizing Buck Regulators

10 Synchronous Buck Switching Regulators from National’s PowerWise Family Offer a Combination of Power Sequencing, Adjustable Switching Frequency and Clock Synchronization Options to Optimize Power Supply Designs.

Nov 5, 2007

November 5, 2007 - National Semiconductor Corporation (NYSE:NSM) today introduced a new line of buck switching regulators that are the first in the industry to feature high power density and self-synchronization.  These 10 full-featured, synchronous buck regulators provide high-efficiency DC-DC power conversion for point-of-load power supply designs in applications such as communication, data storage, industrial and automotive.  Part of National’s PowerWise® energy-efficient product family, the highly integrated regulators feature a variety of input voltages and output currents, and offer a combination of power sequencing, adjustable switching frequency and clock synchronization options. 

The new line of LM201xx and LM202xx synchronous buck regulators includes 2A, 3A, 4A and 5A output current devices.  Each regulator integrates two switching MOSFETs and utilizes an externally compensated peak current-mode control loop, providing superior load transient response in low duty cycle applications.  The external compensation allows the performance to be optimized for the output capacitor and inductor.  With current-mode control, just two external components are needed for compensation.  The ability of the 3A and 4A clock synchronization devices to self-synchronize when in out-of-phase operation reduces input capacitance and voltage ripple in power supply designs.

National offers a downloadable power supply design tool for the new low voltage synchronous buck regulators that eliminates the need for tedious hand calculations.  The tool, in a Microsoft Excel spreadsheet format, calculates component values based on user-specified design parameters to quickly create a complete power supply design.  The design tool allows the design engineer to quickly analyze the control loop response, thermal performance and efficiency of the design.

Technical Features of the New Low-Voltage Buck Regulators
Offered in a 16-pin thermally enhanced TSSOP package, the nine low-voltage buck regulators operate with an input voltage range from 2.95V to 5.5V and deliver up to 5A of continuous output current.  Both fixed and adjustable switching frequency versions are available.

Each buck regulator has a precise internal voltage of 1.5 percent accuracy from -40 degrees C to 125 degrees C while providing excellent line and load regulation.  They include a precision enable pin that allows accurate setting of the turn-on threshold and sequencing of the turn-on of multiple devices, eliminating the need for an external voltage supervisor chip.  Also included is a power good indicator that regulates the output voltage within tolerance and can sequence loads that have an enable input.

A tracking and soft-start feature allows the design engineer to set the output to accurately track an external supply, as well as provide a controlled voltage ramp to protect loads against in-rush current that could cause latch-up.  The monotonic start-up into pre-biased load feature prevents the possibility of latch-up in field programmable gate array (FPGA) and application-specific integrated circuit (ASIC) applications.

The buck regulators enhance system reliability by using an accurate current limit to provide robust protection for long-term hard shorts while minimizing the inductor size.  Over-voltage and under-voltage events are monitored at the output voltage.

The low-voltage LM20123, LM20124 and LM20125 buck regulators feature fixed frequencies of 1.5 MHz at 3A, 1 MHz at 4A or 500 KHz at 5A for enabling the smallest solution size.  For more information on these products, to order samples and an evaluation board, or to download the power supply design tool, visit http://www.national.com/pf/LM/LM20123.html, http://www.national.com/pf/LM/LM20124.html and http://www.national.com/pf/LM/LM20125.html.

The low-voltage LM20143, LM20144 and LM20145 buck regulators feature adjustable frequencies for maximum design flexibility.  For more information on these products, to order samples and an evaluation board, or to download the power supply design tool, visit http://www.national.com/pf/LM/LM20143.html, http://www.national.com/pf/LM/LM20144.html and http://www.national.com/pf/LM/LM20145.html.

The low-voltage LM20133 and LM20134 buck regulators provide clock synchronization for synchronization to an external clock source.  For more information on these products, to order samples and an evaluation board, or to download the power supply design tool, visit http://www.national.com/pf/LM/LM20133.html and http://www.national.com/pf/LM/LM20134.html.

The low-voltage LM20154 buck regulator features out-of-phase clock output for current sharing or out-of-phase operation.  For more information on these products, to order samples and an evaluation board, or to download the power supply design tool, visit http://www.national.com/pf/LM/LM20154.html.

Technical Features of the New High Voltage Buck Regulator
The high-voltage LM20242 buck regulator, offered in a 20-pin TSSOP package with exposed pad, operates with an input voltage range from 4.5V to 36V and delivers up to 2A of continuous output current.  The LM20242 features adjustable frequency from 250 kHz to 1 MHz for maximum design flexibility.  For more information on the LM20242 or to order samples and an evaluation board, visit http://www.national.com/pf/LM/LM20242.html

About National’s PowerWise Brand
National’s PowerWise brand reflects the company’s energy-efficient product portfolio.  It signifies products with outstanding performance-to-power at the component level, as well as products that provide an outstanding, energy-efficient solution when coupled with other National parts.  National’s PowerWise family of products features energy-efficient power management, operational amplifiers, interface and data conversion products.  For more information about National’s PowerWise brand, visit: http://www.national.com/powerwise

About National’s Power Management Products 
National solves power management design problems in space- and energy-constrained applications from feature-rich handheld devices through large line-powered systems. From the novice power designer to the power expert, National’s products, people and design tools enable customers to design green-powered systems with complex power supplies in the shortest amount of time. High-performance products include switching regulators such as National’s flagship SIMPLE SWITCHER® family, and application-specific products including white-LED drivers and Power-over-Ethernet controllers. More information about National’s power management products is available at http://www.national.com/power.

Pricing and Availability
National’s 10 new synchronous buck regulators are available now.  Prices for the products range from $2.30 to $3 in 1,000-unit quantities.

Note to editors:  To view a high-resolution downloadable photo of these products, visit National's photo gallery at http://www.national.com/company/pressroom/gallery/power.html.

About National Semiconductor
National Semiconductor, the industry's premier analog company, creates high-value analog devices and subsystems.  National's leading-edge products include power management circuits, display drivers, audio and operational amplifiers, interface products and data conversion solutions.  National's key analog markets include wireless handsets, displays and a variety of broad electronics markets, including medical, automotive, industrial, and test and measurement applications.  Headquartered in Santa Clara, Calif., National reported sales of $1.93 billion for fiscal 2007, which ended May 27, 2007.  Additional company and product information is available at http://www.national.com