LTC3541 - High Efficiency Buck + VLDO Regulator

The LTC3541 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.

The synchronous buck converter provides a high efficiency output, typically 90%, capable of providing up to 500mA of continuous output current while switching at 2.25MHz, allowing the use of small surface mount inductors and capacitors. A mode-select pin allows Burst Mode operation to be enabled for higher effi ciency at light load currents, or disabled for lower noise, constant frequency operation.

The VLDO regulator provides a low noise, low voltage output capable of providing up to 300mA of continuous output current using only a 2.2μF ceramic capacitor. The input supply voltage of the VLDO regulator (LVIN) may come from the buck regulator or a separate supply.

Features
  • High Efficiency, 500mA Buck Plus 300mA VLDO 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
Typical Application

Applications
  • PDAs/Palmtop PCs
  • Digital Cameras
  • Cellular Phones
  • PC Cards
  • Wireless and DSL Modems
  • Other Portable Power Systems
Packaging
Order Information
Part NumberPackageTempPrice(1-99)Price (1k)*
LTC3541EDD#PBF3x3 DFN-10E$2.70$1.89
LTC3541EDD#TRPBF3x3 DFN-10E$1.95
Demo Boards
Part NumberDescriptionPrice
DC970A-ALTC3541 Demo Board | 3V ≤ VIN ≤ 5.5V, Vout1 (Buck) = 1.8V or 2.5V @ 500mA, Vout2 (VLDO) = 0.8V/1.2V/1.5V/1.8V @ 300mA$100.00
Datasheet
Reliability Data
Press Release
LTspice
Related Product
LTC3541 - High Efficiency Buck + VLDO Regulator
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LTC3541 Footprints and Symbols
LTC3541 Demo Circuit - High Efficiency Buck + VLDO Regulator (4V to 2.5V @ 500mA & 1.8V @ 300mA)