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National Semiconductor Introduces Industry's First Emulated Current-Mode-Controlled Buck-Boost DC-DC Regulator Controller with Ultra-wide Operating Voltage Range

PowerWise Switching Regulator Provides up to 10A from a Wide 3V to 75V Input in Automotive, Telecommunications and Battery-Powered Systems

May 19, 2008

May 19, 2008 - National Semiconductor Corp. (NYSE:NSM) today introduced the industry’s first emulated current-mode-controlled buck-boost DC-DC regulator controller with a best-in-class operating voltage range of 3V to 75V for automotive, telecommunications and battery-powered systems.  The LM5118 features programmable switching frequency up to 500 kHz, ultra-low shutdown current and smooth transition between buck and buck-boost modes.  The LM5118 switching regulator features peak efficiency of 95 percent, positioning it among National’s PowerWise® family of energy-efficient products.

The simple two-switch configuration enables design engineers to easily assemble a complete power converter with ultra-wide input voltage range.  Operation below 3V to 75V makes the LM5118 well-suited for automotive applications such as powering the dashboard display, electronic controls such as anti-lock braking or fuel injection control, and the multitude of microcontrollers used in today’s cars.  These systems operate from a 12.6V battery, but with a weak battery during cold crank conditions, the battery voltage could fall momentarily down to 4V.  To ensure seamless control from electronic modules, the system must still operate at 4V or below.  The unique buck-boost control of the LM5118 makes this seamless control possible.

The control method of the LM5118 is based upon current-mode control utilizing an emulated current ramp.  The patented emulated current-mode control technology provides superior line and load transient response and low duty cycle operation that is not achievable with traditional current-mode control.  

Technical Features of National’s LM5118 Buck-Boost DC-DC Regulator
National’s LM5118 switching regulator features all of the functions necessary to implement an efficient buck-boost regulator, using a minimum of external components.  The buck-boost topology maintains output voltage regulation when the input voltage is either less than or greater than the output voltage, making the product especially suitable for automotive applications.

The LM5118 operates as a buck regulator when the input voltage is sufficiently greater than the regulated output voltage and gradually transitions to the buck-boost mode as the input voltage approaches the output.  This dual-mode approach maintains regulation over a wide range of input voltages with optimal conversion efficiency in the buck mode and a glitch-free output during mode transitions.  The LM5118 includes drivers for the high-side buck MOSFET and the low-side boost MOSFET.  The emulated current-mode control reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable control of very small duty cycles necessary in high-input voltage applications.  Additional protection features include current limit, thermal shutdown and an enable input.

The LM5118 is offered in a 20-pin thermally enhanced TSSOP package.  For more information on the LM5118 or to order samples or an evaluation board, visit http://www.national.com/pf/LM/LM5118.html

About Emulated Current-Mode Technology
Emulated current-mode control overcomes traditional current-mode control’s noise susceptibility by emulating the buck switch current signal, which is then used for current-mode control.  The emulated buck switch current signal is the sum of an emulation ramp current and the sampled diode current just before switching occurs.  Avoiding direct buck switch current measurement minimizes the effect of switching noise, while maintaining the benefits of the current-mode control.

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.

Availability and Pricing
Available now, the LM5118 is priced at $2.92 each in 1,000-unit quantities.

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