Datasheet LTC3541-1 (Analog Devices)

LTC3541-1 High Efficiency Buck + VLDO Regulator
FEATURES DESCRIPTION
n
High Efficiency, 500mA Buck Plus 300mA VLDO™
The LTC®3541-1 combines a synchronous buck DC/
Regulator
DC converter with a very low dropout linear regulator n
Auto Start-Up Powers VLDO/Linear Regulator
(VLDO) to provide up to two output voltages from a single
Output Prior to Buck Regulator Output
input voltage with minimal external components. When n
Independent High Efficiency, 500mA Buck
configured for dual output operation, the LTC3541-1’s auto
(VIN: 2.7V to 5.5V)
start-up feature will bring the VLDO/linear regulator output n
300mA VLDO Regulator with 30mA Standalone Mode
into regulation in a controlled manner prior to enabling the n
No External Schottky Diodes Required
Buck regulator output without the need for external pin n
Buck Output Voltage Range: 0.8V to 5V
control. Buck output prior to VLDO/linear regulator output n
VLDO Input Voltage Range (LVIN): 0.9V to 5.5V
sequencing may also be obtained via external pin control. n
VLDO Output Voltage Range VLDO: 0.4V to 4.1V
The input voltage range is ideally suited for Li-Ion battery- n Selectable Fixed Frequency, Pulse-Skip Operation or powered applications, as well as powering sub-3.3V logic n Burst Mode® Operation from 5V or 3.3V rails. n Short-Circuit Protected The synchronous buck converter provides a high efficiency n Current Mode Operation for Excellent Line and Load output, typically 90%, capable of providing up to 500mA Transient Response of continuous output current while switching at 2.25MHz, n Constant Frequency Operation: 2.25MHz allowing the use of small surface mount inductors and ca- n Low Dropout Buck Operation: 100% Duty Cycle pacitors. A mode-select pin allows Burst Mode operation n Small, Thermally Enhanced, 10-Lead (3mm × 3mm) to be enabled for higher efficiency at light load currents, or DFN Package disabled for lower noise, constant frequency operation.
APPLICATIONS
The VLDO regulator provides a low noise, low voltage n PDAs/Palmtop PCs output capable of providing up to 300mA of continuous n Digital Cameras output current using only a 2.2μF ceramic capacitor. The n Cellular Phones input supply voltage of the VLDO regulator (LVIN) may n PC Cards come from the buck regulator or a separate supply. n L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO is a Wireless and DSL Modems trademark of Linear Technology Corporation. All other trademarks are the property of their respective n Other Portable Power Systems owners. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258.
TYPICAL APPLICATION Buck (Burst) Efficiency and Power Loss vs Load Current
100 1
LTC3541-1 Typical Application
90 VIN EFFICIENCY 2.9V TO 5.5V 80 10µF 0.1 VIN POWER LOSS (W) 70 ENBUCK ENVLDO 2.2µH MODE 60 SW POWER LOSS V 50 0.01 OUT1 VOUT2 2.5V LVIN LVOUT 1.5V 40 200mA 22pF 243k LTC3541-1 412k 300mA EFFICIENCY (%) 30 0.001 10µF BUCKFB LFB 2.2µF 20 115k PGND GND 150k 10 VIN = 3.3V VOUT = 2.5V 0 0.0001 35411 TA01a 1 10 100 1000 LOAD CURRENT (mA) 35411 TA01b 35411fb For more information www.linear.com/LTC3541-1 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Related Parts