MAX1734

19-1586; Rev 0; 7/00 MAX1733/MAX1734 Low-Voltage, Step-Down DC-DC Converters in SOT23 General Description The MAX1733/MAX1734 step-down DC-DC converters deliver over 250mA to outputs as low as 1.25V. These converters use a unique proprietary current-limited control scheme that achieves over 90% efficiency. These devices maintain extremely low quiescent supply current (40µA), and their high 1.2MHz (max) operating frequency permits small, low-cost external components. This combination of features makes the MAX1733/ MAX1734 excellent high-efficiency alternatives to linear regulators in space-constrained applications. Internal synchronous rectification greatly improves efficiency and eliminates the external Schottky diode required in conventional step-down converters. Both devices also include internal digital soft-start to limit input current upon startup and reduce input capacitor requirements. The MAX1733 provides an adjustable output voltage (1.25V to 2.0V). The MAX1734 provides factory-preset output voltages (see Selector Guide). Both are available in space-saving 5-pin SOT23 packages. Applications Cellular, PCS, and Cordless Telephones PDAs, Palmtops, and Handy-Terminals Battery-Powered Equipment Typical Operating Circuit Features o 250mA Guaranteed Output Current o Synchronous Rectifier for Over 90% Efficiency o Tiny 5-Pin SOT23 Package o 40µA Quiescent Supply Current o 0.01µA Logic-Controlled Shutdown o Up to 1.2MHz Switching Frequency o Fixed 1.8V or 1.5V Outputs (MA...