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National buck regulator controller eyes high-current apps

Posted: 15 Feb 2005 ?? ?Print Version ?Bookmark and Share

Keywords:national semiconductor? lm2657? buck regulator controller? controller?

National Semiconductor Corp. rolled out an adjustable 200kHz to 500kHz dual-channel, voltage-mode-controlled, high-speed synchronous buck regulator controller engineered for high-current applications.

According to the press release, the LM2657 requires only N-channel FETs for both the upper and lower positions of each stage. It features line feed-forward to improve the response to input transients. And at very light loads, the user can choose between the high-efficiency pulse-skip mode or the constant frequency forced-PWM mode. Loss-less current limiting without the use of external sense resistors is made possible by sensing the voltage drop across the bottom FET, and an adaptive duty cycle clamping technique is incorporated to reduce peak currents under abnormal load conditions. Additionally, the two independently programmable outputs switch 180 degrees out of phase (interleaved switching), reducing the input capacitor and filter requirements.

The LM2657's input voltage range is from 4.5V to 28V, while the output voltages are adjustable down to 0.6V. The device includes under-voltage lockout, over-voltage/under-voltage protection and soft-start.

Housed in a TSSOP-28 package, the LM2657 is priced at $2.75 each in 1,000-unit quantities.

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