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National Semiconductor Introduces Industry's Widest Range Input-Voltage Dual Synchronous Buck Controller with Oscillator Synchronization

Jun 9, 2003

June 9, 2003 - Extending its leadership in power management for communications systems, National Semiconductor Corporation (NYSE: NSM) today launched a high-voltage, two-phase synchronous switching controller tailored for power supply designs for communications, industrial and automotive applications.  Its wide input voltage range (4.5 V to 36 Vin) makes the feature-rich device a low-cost, point-of-load (POL) regulator solution for Distributed Power Architectures (DPAs).  Shipping now, the new device is ideal for applications where multiple high current, low voltage power supplies are needed to power system loads with multiple voltages, such as FPGAs, DSPs and microprocessors.  

National Semiconductor's LM5642 is flexible, operating in two modes, providing two outputs, or in bi-phase mode for a single output with twice the load current.  The current-mode control loop can use either a discrete current sense resistor or top-side N-Channel MOSFET RDS(ON) sensing, over a broad conversion range, i.e. 36 Vin and 1.8 Vout. 

"The digital ASIC and DSP content of the systems powered by DPAs is increasing, so is the number of low voltages required at the point of load," said Paul Greenland, marketing director of National Semiconductor's power management group.  "A dual regulator is particularly useful in this environment.  Smart sequencing is also essential as the number of rails increases to prevent latch-up and misoperation of complex loads.  The LM5642 has the built-in flexibility to meet emerging requirements."

Enabling high conversion ratios with up to 95 percent efficiency, National's LM5642 controller is ideal for any of the new DPAs with bus voltages such as 5 V, 12 V, 24 V and up to 36 V.  It also can be combined with National's recently announced 100 V Push-Pull controller (LM5030) to provide secondary post-regulation in multiple output isolated DC-DC power modules.

The LM5642 oscillator frequency can be synchronized up or down between 150 and 250 kHz, allowing users to mitigate switching frequency interference.  It can run at 200 kHz where two controllers operate 180 degrees out of phase, significantly reducing the input filter capacitance in high current applications where the device is used as a single-output regulator.
Each output of the LM5642 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 a wide input voltage range.  The combination of independent channel enable and soft-start pins makes power sequencing easy.  Wide loop bandwidth results in fast response to load transients and rejection of line transients.  These features, and more others, make the LM5642 perfectly suited for projects that need multiple, efficient supplies. 

National has developed power management technology for a wide range of applications including communication infrastructure, wireless handsets and other portable devices, servers and PCs.  More information about National’s power expertise is available at http://power.national.com.

Packaging, Pricing and Availability
National Semiconductor's LM5642 dual synchronous switching controller in a TSSOP-28 package is available today.  It is priced at $1.85 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 analog-based semiconductor products, which include stand-alone devices and subsystems in the areas of power management, imaging, display drivers, audio, amplifiers and data conversion. The company targets key markets such as wireless, displays, PC and networking, and a broad range of portable applications. With headquarters in Santa Clara, California, National reported sales of $1.5 billion for its most recent fiscal year. Additional company and product information is available on the World Wide Web at www.national.com