LTC3548

LTC3548 Dual Synchronous, 400mA/800mA, 2.25MHz Step-Down DC/DC Regulator FEATURES n High Efficiency: Up to 95% n Very Low Quiescent Current: Only 40μA n Low Output Ripple Burst Mode® Operation n 2.25MHz Constant-Frequency Operation n High Switch Current: 0.7A and 1.2A n No Schottky Diodes Required n Low RDS(ON) Internal Switches: 0.35Ω n Current Mode Operation for Excellent Line and Load Transient Response n Short-Circuit Protected n Low Dropout Operation: 100% Duty Cycle n Ultralow Shutdown Current: IQ < 1μA n Output Voltages from 5V down to 0.6V n Power-On Reset Output n Externally Synchronizable Oscillator n Small Thermally Enhanced MSOP and 3mm × 3mm DFN Packages APPLICATIONS ■ PDAs/Palmtop PCs ■ Digital Cameras ■ Cellular Phones ■ Portable Media Players ■ PC Cards ■ Wireless and DSL Modems DESCRIPTION The LTC®3548 is a dual, constant-frequency, synchronous step down DC/DC converter. Intended for low power applications, it operates from 2.5V to 5.5V input voltage range and has a constant 2.25MHz switching frequency, allowing the use of tiny, low cost capacitors and inductors with a profile ≤1mm. Each output voltage is adjustable from 0.6V to 5V. Internal synchronous 0.35Ω, 0.7A/1.2A power switches provide high efficiency without the need for external Schottky diodes. A user selectable mode input is provided to allow the user to trade-off noise ripple for low power efficiency. Burst Mode operation provides high efficiency at light loads, while pulse-skipping mode provides low...