National Semiconductor Corp. has introduced a cascaded pulsewidth-modulated (PWM) DC/DC controller with integrated functions that allow it, according to the company, to step down a 48V input to a sub-1V input without the timing problems encountered by other controllers.
National's LM5041 integrates a fully synchronous buck converter and push-pull controller on the same die. This eases design of PWM power systems that use DC/DC converters, as well as design of embedded power systems on communications motherboards, according to Don Ashley, strategic marketing manager for high-voltage power IC products at National, Santa Clara, Calif.
"Not many companies have done what we've done," Ashley said. "We've doubled the level of integration."
The controller chops the 48V input through the synchronous buck converter, then steps it down to the low voltage required by the load. This cascaded approach achieves high power-conversion efficiency by keeping chip propagation delays under 100ns, minimizing switching losses, according to Ashley.
Chip functions include a start-up bias regulator with a range of 15 to 100V, user-programmable soft-start circuitry, and a 1MHz oscillator with external clock synchronization capability.
The integrated design eliminates external parts such as a feedback regulator, high-voltage start-up regulator, and output filter inductors, minimizing the controller's susceptibility to electromagnetic radiation, according to National.
The company offers a companion pair of mating half-bridge power MOSFET drivers, the LM5101 and LM- 5102, both of which are rated up to 100V. The drivers enable designers to size external MOSFETs to the power delivery needs of the DC/DC converter. The LM5102 adds programmable rise-time control.
National's controller comes in an LLP-16 package that has tiny leads but no traditional lead frame, which lowers thermal impedance and improves heat dissipation, Ashley said.
In quantities of 1,000, the LM5041 is priced at $2.55. The LM5101 and LM5102 MOSFET drivers are priced at $1.75 and $1.79, respectively, in the same quantities.
Samples will be available in April, with volume production scheduled to begin in the third quarter at National's fabs in Arlington, Texas, and Greenock, Scotland.