ADI LTC3541EDD#PBF

The TC3541 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 efficiency 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.

• 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: 0.81 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

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