5V/Adjustable Step-Up Current-Mode DC-DC Converters

The MAX731 and MAX752 are fixed and adjustable CMOS, step-up, DC-DC switch-mode regulators. The MAX731 accepts a positive input voltage between +2.5V and +5.25V and converts it to a fixed +5V at 200mA, guaranteed over temperature. Typical full-load efficien­cies are 82% to 87%. It requires a single inductor value of 22µH to function over the entire range, so no inductor­ related design is necessary. The MAX752 is an adjusta­ble version that converts a minimum of + 1.8V to any higher voltage up to +15V, at up to 200mA. Typical full-load efficiencies are 85% to 95%. A single 50µH inductor is suitable for the entire range of operating conditions, so no inductor-related design is necessary.

The MAX731/MAX752 use current-mode pulse-width modulation (PWM) controllers to provide precise output regulation and low subharmonic noise. Typical no-load supply current is 2mA. A fixed 170kHz oscillator fre­quency allows easy filtering of ripple and noise, and provides for small external components.

The MAX731/MAX752 feature cycle-by-cycle current lim­iting, overcurrent limiting, external shutdown, and pro­grammable soft-start protection.

For fixed + 12V and + 15V step-up regulators, refer to the MAX732/MAX733 data sheet. For lower-power step-up applications, refer to the MAX631/632/633 and MAX654-659 data sheets.

APPLICATIONS

* +5V-Logic Supply in +3V-Logic System

* DC-DC Converter Module Replacement

* Portable Instruments

* Laptop Computers

* Distributed Power Systems

* Cellular Phones

* Battery-Powered Equipment

* 200mA Load Currents Guaranteed with No External MOSFET

* Step-Up from a 2.5V Input

* 170kHz High-Frequency Current-Mode PWM

* 82% to 87% Typical Efficiencies at Full Load (MAX731)

* 85% to 95% Typical Efficiencies at Full Load (MAX752)

* Small Inductor - No Component Design Required

* 2mA Quiescent Current (MAX752)

* Overcurrent and Soft-Start Protection

* 8-Pin DIP, 16-Pln Wide SO Packages

* Shutdown Pin