Datasheet LTC3541-2 (Analog Devices)

LTC3541-2 High Efficiency Buck + VLDO Regulator
FEATURES DESCRIPTION
n
High Efficiency, 500mA Buck Plus 300mA VLDO
The LTC®3541-2 combines a synchronous buck DC/
Regulator
DC converter with a very low dropout linear regulator n
Auto Start-Up Powers Buck Output Prior to VLDO/
(VLDOTM regulator) and internal feedback resistor networks
Linear Regulator Output
to provide two output voltages from a single input volt- n
Independent 500mA High Efficiency Buck
age with minimal external components. When configured
(VIN: 2.7V to 5.5V)
for dual output operation, the LTC3541-2’s auto start-up n
300mA VLDO Regulator with 30mA Standalone Mode
feature wil bring the 1.875V buck output into regulation n
No External Schottky Diodes Required
in a controlled manner, prior to enabling the 1.5V VLDO n
Fixed Buck Output Voltage: 1.875V
output without the need for external pin control. The 1.5V n
VLDO Input Voltage Range (LVIN: 1.6V to 5.5V)
VLDO/linear regulator output prior to 1.875V buck output n
Fixed VLDO Output Voltage: 1.5V
sequencing may also be obtained via external pin control. n Selectable Fixed Frequency, Pulse-Skip Operation The input voltage range is ideally suited for Li-Ion battery n or Burst Mode® Operation applications powering sub-3.3V logic 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%. It can provide up to 500mA of output Transient Response current while switching at 2.25MHz, allowing the use of n Shutdown Current: <3µA small surface mount inductors and capacitors. A mode- n Constant Frequency Operation: 2.25MHz select pin allows Burst Mode operation to be enabled for n Low Dropout Buck Operation: 100% Duty Cycle higher efficiency at light load currents, or disabled for lower n Small, Thermally Enhanced, 10-Lead (3mm × 3mm) noise, constant frequency operation. DFN Package The VLDO regulator provides a low noise, low voltage
APPLICATIONS
output capable of providing up to 300mA of output current using only a 2.2µF ceramic capacitor. The input supply n Digital Cameras voltage of the VLDO regulator (LVIN) may come from the n Cellular Phones buck regulator output or a separate supply. n PC Cards L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO is a n Wireless and DSL Modems trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258. n Other Portable Power Systems
TYPICAL APPLICATION Buck (Burst) Efficiency vs Load Current
V 100 1 IN VIN = 3V 2.9V TO 5.5V 10µF 90 EFFICIENCY VIN 80 ENBUCK ENVLDO 0.1 POWER LOSS (W) V 70 OUT1 2.2µH 1.875V SW MODE 60 200mA LTC3541-2 POWER LOSS 50 0.01 VOUT V 40 OUT2 LV EFFICIENCY (%) IN LVOUT 1.5V 30 300mA 0.001 10µF 2.2µF PGND GND 20 10 35412 TA01a 0 0.0001 1 10 100 1000 LOAD CURRENT (mA) 35412 TA01b 35412fc For more information www.linear.com/LTC3541-2 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 Operation Applications Information Package Description Revision History Related Parts