MAX746

19-0192; Rev 1; 11/93 High-Efficiency, PWM, Step-Down, N-Channel DC-DC Controller _______________General Description The MAX746 is a high-efficiency, high-current, step-down DC-DC power-supply controller that drives external N-channel FETs. It provides 93% to 96% efficiency from a 6V supply voltage with load currents ranging from 50mA up to 3A. It uses a pulse-width-modulating (PWM) current-mode control scheme to provide precise output regulation and low output noise. The MAX746's 4V to 15V input voltage range, fixed 5V/adjustable (Dual-ModeTM) output, and adjustable current limit make this device ideal for a wide range of applications. High efficiency is maintained with light loads due to a proprietary automatic pulse-skipping control (Idle-ModeTM) scheme that minimizes switching losses by reducing the switching frequency at light loads. The low 950µA quiescent current and ultra-low 1.4µA shutdown current further extend battery life. External components are protected by the MAX746's cycleby-cycle current limit. The MAX746 also features a 2V ±1.5% reference, a comparator for low-battery detection or level translating, and soft-start and shutdown capability. The MAX747—discussed in a separate data sheet— functions similarly to the MAX746, but drives P-channel logic level FETs. ____________________________Features o 93% to 96% Efficiency for 50mA to 3A Output Currents o 4V to 15V Input Voltage Range o Low 950µA Supply Current o 1.4µA Shutdown Current o Drives External N-Chann...