NATIONAL Semiconductor, represented by Arrow Electronics, has announced the LM2657, an adjustable 200kHz to 500kHz dual-channel, voltage-mode-controlled, high-speed synchronous buck regulator controller ideal for high-current applications.
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.
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.
A unique adaptive duty cycle clamping technique is incorporated to significantly reduce peak currents under abnormal load conditions.
The two independently programmable outputs switch 180 degrees out of phase (interleaved switching), reducing the input capacitor and filter requirements.
The input voltage range is 4.5V to 28V, while the output voltages are adjustable down to 0.6V.