LM2657 Datasheet | National Semiconductor

Description The LM2657 is an adjustable 200k Hz-500k Hz dual channel voltage-mode controlled high-speed synchronous buck regulator controller ideally suited for high current applications. The LM2657 requires only N-channel FETs for both the upper and lower positions of each stage. It features line feedforward to improve the response to input transients. At very light loads, the user can choose between the highefficiency Pulse-skip mode or the constant frequency Forced-PWM mode. Lossless 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˚ 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. Standard supervisory and control features include Soft-start, Power Good, output Under-voltage and Over-voltage protection, Under-voltage Lockout, and chip Enable. Features n n n n n n n n n n n n n n n Input voltage range from 4.5V to 28V Synchronous dual-channel interleaved switching Forced-PWM or Pulse-skip modes Lossless bottom-side FET current sensing Adaptive duty cycle clamp High current N-channel FET drivers Low shutdown supply current Reference voltage accurate to within ± 1.5% Output voltage adjustable down to 0.6V Power Good flag and Chip Enable Under-voltage lockout Over-voltage/Under-voltage protection Soft-start Switching frequency adjustable 200k Hz-500k Hz TSSOP-28 package Applications n Low Output Voltage High-Efficiency Buck Regulators Typical Application (Channel 2 in parenthesis) © 2005 National Semiconductor Corporation DS201347 .national. Typical Application (Channel 2 in parenthesis) Connection Diagram (Continued) Top View Ordering...