MAX1626

19-1075; Rev 0; 6/96 NUAL KIT MA ATION SHEET A EVALU T A D WS FOLLO 5V/3.3V or Adjustable, 100% Duty-Cycle, High-Efficiency, Step-Down DC-DC Controllers ____________________________Features o Low Dropout Voltage o 100% Maximum Duty Cycle o Soft-Start Limits Start-Up Current o Efficiency >90% (3mA to 2A Loads) o Output Power >12.5W o 90µA Max Quiescent Current o 1µA Max Shutdown Current o Up to 300kHz Switching Frequency o 16.5V Max Input Voltage o Output Voltage: 5V/3.3V (MAX1626) Adjustable (MAX1627) o Current-Limited Control Scheme _______________General Description The MAX1626/MAX1627 step-down DC-DC switching controllers provide high efficiency over loads ranging from 1mA to more than 2A. A unique current-limited, pulse-frequency-modulated (PFM) control scheme operates with up to a 100% duty cycle, resulting in very low dropout voltages. This control scheme eliminates minimum load requirements and reduces the supply current under light loads to 90µA (versus 2mA to 10mA for common pulse-width modulation controllers). These step-down controllers drive an external P-channel MOSFET, allowing design flexibility for applications to 12W or higher. Soft-start reduces current surges during start-up. A high switching frequency (up to 300kHz) and operation in continuous-conduction mode allow the use of tiny surface-mount inductors. Output capacitor requirements are also reduced, minimizing PC board area and system costs. The output voltage is preset at 5V or 3.3V for the MAX1626 ...