High-Efficiency, PWM, Step-Down, N-Channel DC-DC Controller

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-Mode™) 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-Mode™) 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 cycle-by-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.

Applications

* 5V to 3.3V Green PC Applications * Battery-Powered Applications * Cell Phones * Notebook Computers * PDAs and Other Handheld Devices

* 93% to 96% Efficiency for 50mA to 3A Output Currents

* 4V to 15V Input Voltage Range

* Low 950µA Supply Current

* 1.4µA Shutdown Current

* Drives External N-Channel FETs

* Fixed-Frequency Current-Mode PWM (Heavy Loads)

* Idle-Mode PFM (Light Loads)

* Cycle-by-Cycle Current Limiting

* 2V ±1.5% Accurate Reference Output

* Adjustable Soft-Start

* Undervoltage Lockout

* Precision Comparator for Power-Fail or Low-Battery Warning