June 5, 2002 - A new two-phase synchronous switching controller from National Semiconductor (NYSE: NSM), designed to address the power regulation requirements in next-generation systems, provides accurate and cost-effective dual voltage power regulation. The input voltage range, control mode, feature set and overall architecture of National?s new LM2642 were designed from the ground up to meet the needs of line-powered systems.
Most line-powered systems distribute 5 V and 3.3 V rails from a multi-output off-line supply. This approach uses a half-wave rectifier that unnecessarily reduces overall efficiency. In addition, post-secondary regulators develop the required core voltages and are usually non-synchronous switchers. These switchers use a catch diode which forces efficiencies to as low as 70 percent. National?s LM2642 dual regulator controller overcomes these problems and enables up to 95 percent conversion efficiency for applications such as set-top boxes, home gateways, cable modems and a wide variety of industrial applications.
?National?s LM2642 allows system architects to cut system costs and greatly increase conversion efficiency by distributing a single 5 V, 12 V or 20 V rail and developing the required supply voltages locally. The LM2642?s feature set, ease of use and high performance make it a perfect solution for point-of-load regulation requirements in line-powered applications,? said John Perzow, strategic marketing manager of National?s Power Management Group.
Synchronous operation is essential for high-efficiency conversation when the output voltage is low (<3.3 V) or the duty cycle is less than 50 percent (output voltage divided by input voltage). National?s LM2642 is ideal for developing either multiple voltages or a single high-current voltage. This new 300 kHz dual synchronous solution boasts a 4.5 V to 30 V input voltage range and uses current-mode control for high performance over this range. It drives low-cost N-channel MOSFETs and allows designers to easily sequence the two channels.
National?s LM2642 consists of two current-mode synchronous buck regulator controllers with a switching frequency of 300 kHz for best conversion efficiency. The two controllers operate 180 degrees out of phase, which significantly reduces the required input capacitance and allows the device to be used as a single-output regulator for high-current applications.
Each output of the LM2642 can be set from 1.3 V to 13.5 V. Current-mode control with or without a current-sense resistor ensures superior line and load regulation over its wide input voltage range. The power-good function combined with independent enable and soft-start pins makes power sequencing easy. Wide loop bandwidth results in very fast response to load transients. These features and more make the LM2642 perfectly suited for projects that need multiple, efficient supplies, but where there is no time to waste on complex power supply design. More information is available at: http://www.national.com/pf/LM/LM2642.html
Packaging, Pricing and Availability
National Semiconductor?s LM2642 dual synchronous switching controller, housed in a TSSOP-28 package, is shipping now. It is priced at $2.28 each in 1,000 units.
About National Semiconductor
National Semiconductor is the premier analog company driving the information age. Combining real-world analog and state-of-the-art digital technology, the company is focused on the fast growing markets for wireless handsets; displays; information infrastructure, and information appliances. With headquarters in Santa Clara, California, National reported sales of $2.1 billion for its last fiscal year and has about 9,800 employees worldwide. Additional company and product information is available on the World Wide Web at www.national.com.
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