3.3V/5V/Adjustable-Output, Step-Up DC-DC Converters

The MAX756/MAX757 are CMOS step-up DC-DC switching regulators for small, low input voltage or battery-powered systems. The MAX756 accepts a positive input voltage down to 0.7V and converts it to a higher pin-selectable output voltage of 3.3V or 5V. The MAX757 is an adjustable version that accepts an input voltage down to 0.7V and generates a higher adjustable output voltage in the range from 2.7V to 5.5V. Typical full-load efficiencies for the MAX756/MAX757 are greater than 87%.

The MAX756/MAX757 provide three improvements over previous devices. Physical size is reduced-the high switching frequencies (up to 0.5MHz) made possible by MOSFET power transistors allow for tiny (< 5mm diameter) surface-mount magnetics. Efficiency is improved to 87% (10% better than with low-voltage regulators fabricated in bipolar technology). Supply current is reduced to 60µA by CMOS construction and a unique constant-off-time pulse-frequency modulation control scheme.

Applications

* 2-Cell and 3-Cell Battery-Operated Equipment * 3.3V to 5V Step-Up Conversion * Glucose Meters * Medical Instrumentation * Palmtop Computers * Personal Data Communicators/Computers * Portable Data-Collection Equipment

* Operates Down to 0.7V Input Supply Voltage

* 87% Efficiency at 200mA

* 60µA Quiescent Current

* 20µA Shutdown Mode with Active Reference and LBI Detector

* 500kHz Maximum Switching Frequency

* ±1.5% Reference Tolerance Over Temperature

* Low-Battery Detector (LBI/LBO)

* 8-Pin DIP and SO Packages