DESCRIPTION
The LTC®3541-2 combines a synchronous buck DC/DC converter with a very low dropout linear regulator (VLDOTMregulator)andinternalfeedbackresistornetworks to provide two output voltages from a single input voltage with minimal external components. When configured for dual output operation, the LTC3541-2’s auto start-up feature will bring the 1.875V buck output into regulation in a controlled manner, prior to enabling the 1.5V VLDO output without the need for external pin control. The 1.5V VLDO/linear regulator output prior to 1.875V buck output sequencing may also be obtained via external pin control. The input voltage range is ideally suited for Li-Ion battery applications powering sub-3.3V logic from 5V or 3.3V rails.

FEATURES
■ High Efficiency, 500mA Buck Plus 300mA VLDO
   Regulator
      Auto Start-Up Powers Buck Output Prior to VLDO/
      Linear Regulator Output
■ Independent 500mA High Efficiency Buck
   (VIN: 2.7V to 5.5V)
■ 300mA VLDO Regulator with 30mA Standalone Mode
■ No External Schottky Diodes Required
■ Fixed Buck Output Voltage: 1.875V
■ VLDO Input Voltage Range (LVIN: 1.6V to 5.5V)
■ Fixed VLDO Output Voltage: 1.5V
■ Selectable Fixed Frequency, Pulse-Skip Operation
   or Burst Mode® Operation
■ Short-Circuit Protected
■ Current Mode Operation for Excellent Line and Load
   Transient Response
■ Shutdown Current: <3µA
■ Constant Frequency Operation: 2.25MHz
■ Low Dropout Buck Operation: 100% Duty Cycle
■ Small, Thermally Enhanced, 10-Lead (3mm × 3mm)
   DFN Package

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