DESCRIPTION
The LTC®3541 combines a synchronous buck DC/DC converter with a very low dropout linear regulator (VLDO) to provide up to two output voltages from a single input voltage with minimal external components. When configured for dual output operation, the LTC3541’s auto start-up feature will bring the Buck output into regulation in a controlled manner prior to enabling the VLDO regulator output without the need for external pin control. VLDO/linear regulator output prior to Buck output sequencing may also be obtained via external pin control. The input voltage range is ideally suited for Li-Ion battery-powered applications, as well as powering sub-3.3V logic from 5V or 3.3V rails.

FEATURES
■ High Efficiency, 500mA Buck Plus 300mA VLDOTM
   Regulator
   Auto Start-Up Powers Buck Output Prior to
   VLDO/Linear Regulator Output
■ Independent High Efficiency, 500mA Buck
   (VIN: 2.7V to 5.5V)
■ 300mA VLDO Regulator with 30mA Standalone Mode
■ No External Schottky Diodes Required
■ Buck Output Voltage Range: 0.8V to 5V
■ VLDO Input Voltage Range (LVIN): 0.9V to 5.5V
■ VLDO Output Voltage Range VLDO: 0.4V to 4.1V
■ Selectable Fixed Frequency, Pulse-Skip Operation or
   Burst Mode® Operation
■ Short-Circuit Protected
■ Current Mode Operation for Excellent Line and Load
   Transient Response
■ Constant Frequency Operation: 2.25MHz
■ Low Dropout Buck Operation: 100% Duty Cycle
■ Small, Thermally Enhanced, 10-Lead (3mm × 3mm)
   DFN Package

APPLICATIONS
■ PDAs/Palmtop PCs
■ Digital Cameras
■ Cellular Phones
■ PC Cards
■ Wireless and DSL Modems
■ Other Portable Power Systems