LTC3541-3 Datasheet | Linear Technology

High Efficiency Buck + VLDO Regulator Features nn High Efficiency 500m A Buck Plus 300m A VLDO Regulator nn Auto Start-Up Powers VLDO/Linear Regulator Output Prior to Buck Output nn Independent 500m A High Efficiency Buck (VIN: 2.7V to 5.5V) nn 300m A VLDO Regulator with 30m A Standalone Mode nn No External Schottky Diodes Required nn Fixed Buck Output Voltage: 1.8V nn VLDO Input Voltage Range (LVIN: 1.675V to 5.5V) nn Fixed VLDO Output Voltage: 1.575V nn Selectable Fixed Frequency, Pulse-Skip Operation or Burst Mode® Operation nn Short-Circuit Protected nn Current Mode Operation for Excellent Line and Load Transient Response nn Shutdown Current: <3µA nn Constant Frequency Operation: 2.25MHz nn Low Dropout Buck Operation: 100% Duty Cycle nn Small, Thermally Enhanced, 10-Lead (3mm × 3mm) DFN Package APPLICATIONS nn Digital Cameras nn Cellular Phones nn PC Cards nn Wireless and DSL Modems nn Other Portable Power Systems DESCRIPTION The LTC®3541-3 bines a synchronous buck DC/DC converter with a very low dropout linear regulator (VLDO™ regulator) and internal feedback resistor networks to provide two output voltages from a single input voltage with minimum external ponents. When configured for dual output operation, the LTC3541-3’s auto start-up feature will bring the 1.575V VLDO/linear regulator output into regulation in a controlled manner prior to enabling the 1.8V buck output without the need for external pin control. The 300m A VLDO/linear regulator output will source only 30m A until the buck output achieves regulation. The input voltage range is ideally suited for applications powered from a Li-Ion battery and 5V or 3.3V rails. The synchronous buck converter provides a high efficiency output, typically 90%. It can provide up to 500m A of 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 efficiency at light load currents, or...