Product category: Power Supply ICs and Controllers
News Release from: National Semiconductor | Subject: LM2642
Edited by the Electronicstalk Editorial Team on 17 June 2002
Regulator raises line-powered system
efficiency
A new two-phase synchronous switching controller, designed to address the power regulation requirements in next-generation systems, provides accurate and cost-effective dual voltage power regulation.
A new two-phase synchronous switching controller from National Semiconductor, 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 the LM2642 were designed from the ground up to meet the needs of line-powered systems
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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Most line-powered systems distribute 5 and 3.3V rails from a multi-output offline 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.
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These switchers use a catch diode which forces efficiencies to as low as 70%.
National's LM2642 dual regulator controller overcomes these problems and enables up to 95% 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, 12 or 20V 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 Monika Abele, product marketing engineer Europe in the power management group at National Semiconductor.
Synchronous operation is essential for high-efficiency conversation when the output voltage is low (less than 3.3V) or the duty cycle is less than 50% (output voltage divided by input voltage).
The LM2642 is ideal for developing either multiple voltages or a single high-current voltage.
This new 300kHz dual synchronous solution boasts a 4.5 to 30V 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 300kHz 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 to 13.5V.
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.
National Semiconductor's LM2642 dual synchronous switching controller, housed in a TSSOP-28 package, is shipping now, priced at $2.28 each in 1000 units.
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