National switching controller delivers up to 95 percent efficiency

National Semiconductor Corp. has announced the release of the LM2642 two-phase synchronous switching controller that delivers up to 95 percent conversion efficiency for line-powered systems such as STBs, home gateways, cable modems, and other industrial applications.

Most line-powered systems distribute 5V and 3.3V rails from a multi-output off-line supply that uses a half-wave rectifier, which 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 allows system architects to cut system costs and greatly increase conversion efficiency by distributing a single 5V, 12V or 20V rail and developing the required supply voltages locally," claims John Perzow, strategic marketing manager of National's Power Management Group.

The LM2642 is suited for developing either multiple voltages or a single high-current voltage. The dual synchronous solution has an input voltage range of 4.5V to 30V and uses current-mode control over this range. It drives low-cost N-channel MOSFETs and allows designers to easily sequence the two channels.

The TSSOP-28 device consists of two current-mode synchronous buck regulator controllers with a switching frequency of 300kHz. The two controllers operate 1800 out of phase to reduce 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 1.3V to 13.5V, while the power-good function combined with independent enable and soft-start pins simplifies power sequencing.

The LM2642 is priced at $2.28 each in 1,000 units.