MAX747

19-0171; Rev 1; 9/93 High-Efficiency PWM, Step-Down P-Channel DC-DC Controller _______________General Description The MAX747 high-efficiency, high-current, step-down controller drives external P-channel FETs. It provides 90% to 95% efficiency from a 6V supply with load currents ranging from 50mA up to 2.5A. It uses a pulse-width-modulating (PWM) current-mode control scheme to provide precise output regulation and low output noise. The MAX747’s 4V to 15V input voltage range, a fixed 5V/adjustable (Dual-Mode™) output, and a current limit set with an external resistor make this device ideal for a wide range of applications. High efficiency is maintained with light loads due to a proprietary dual-control (Idle-Mode™) scheme that minimizes switching losses by reducing the switching frequency at light loads. The low 800µA quiescent current and ultra-low 0.6µA shutdown current further extend battery life. External components are protected by the MAX747’s cycle-by-cycle current limit. The MAX747 also features a 2V ±1.5% reference, a comparator for low-battery detection or level translating, as well as soft-start and shutdown capability. The MAX746, discussed in a separate data sheet, functions similarly to the MAX747, but it drives N-channel logic level FETs on the high side. ____________________________Features o 90% to 95% Efficiency for 50mA to 2.5A Output Currents o 4V to 15V Input Voltage Range o Low 800µA Supply Current o 0.6µA Shutdown Current o Drives External P-Channel FET...