Datasheet LTC3541-3 (Analog Devices)

LTC3541-3 High Efficiency Buck + VLDO Regulator
FEATURES DESCRIPTION
n
High Efficiency 500mA Buck Plus 300mA VLDO
The LTC®3541-3 combines a synchronous buck DC/DC
Regulator
converter with a very low dropout linear regulator (VLDO™ n
Auto Start-Up Powers VLDO/Linear Regulator
regulator) and internal feedback resistor networks to
Output Prior to Buck Output
provide two output voltages from a single input voltage n
Independent 500mA High Efficiency Buck
with minimum external components. When configured
(VIN: 2.7V to 5.5V)
for dual output operation, the LTC3541-3’s auto start-up n
300mA VLDO Regulator with 30mA Standalone Mode
feature will bring the 1.575V VLDO/linear regulator output n
No External Schottky Diodes Required
into regulation in a controlled manner prior to enabling the n
Fixed Buck Output Voltage: 1.8V
1.8V buck output without the need for external pin control. n
VLDO Input Voltage Range (LVIN: 1.675V to 5.5V)
The 300mA VLDO/linear regulator output will source only n
Fixed VLDO Output Voltage: 1.575V
30mA until the buck output achieves regulation. The input n Selectable Fixed Frequency, Pulse-Skip Operation voltage range is ideally suited for applications powered or Burst Mode® Operation from a Li-Ion battery and 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 smal 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 (LV n Cellular Phones IN) may come from the buck regulator 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 n owners. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258. Other Portable Power Systems
TYPICAL APPLICATION Buck (Burst) Efficiency vs Load Current LTC3541-3 Typical Application
100 1 VIN = 3V 90 VIN EFFICIENCY 3V TO 5.5V 80 10µF 0.1 V POWER LOSS (W) IN 70 ENBUCK ENVLDO 60 VOUT1 2.2µH POWER 1.8V SW MODE 50 0.01 LOSS 200mA LTC3541-3 40 V EFFICIENCY (%) OUT 30 VOUT2 0.001 LVIN LVOUT 1.575V 20 300mA 10 10µF 2.2µF PGND GND 0 0.0001 1 10 100 1000 35413 TA01a LOAD CURRENT (mA) 35413 TA01b 35413fd For more information www.linear.com/LTC3541-3 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