LTC3541 データシートの表示（PDF） - Linear Technology

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LTC3541

High Efficiency Buck + VLDO Regulator

Linear Technology 

FEATURES

nn High Efficiency, 500mA Buck Plus 300mA VLDO™

Regulator

nn Auto Start-Up Powers Buck Output Prior

to VLDO/Linear Regulator Output

nn Independent High Efficiency, 500mA Buck

(VIN: 2.7V to 5.5V)

nn 300mA VLDO Regulator with 30mA Standalone Mode

nn No External Schottky Diodes Required

nn Buck Output Voltage Range: 0.8V to 5V

nn VLDO Input Voltage Range (LVIN): 0.9V to 5.5V

nn VLDO Output Voltage Range VLDO: 0.4V to 4.1V

nn Selectable Fixed Frequency, Pulse-Skip Operation or

nn Burst Mode® Operation

nn Short-Circuit Protected

nn Current Mode Operation for Excellent Line and Load

Transient Response

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 PDAs/Palmtop PCs

nn Digital Cameras

nn Cellular Phones

nn PC Cards

nn Wireless and DSL Modems

nn Other Portable Power Systems

LTC3541

High Efficiency

Buck + VLDO Regulator

DESCRIPTION

The LTC®3541 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 ca-

pacitors. 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.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO is a

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.

TYPICAL APPLICATION

Buck (Burst) Efficiency and Power Loss vs Load Current

VIN

2.9V TO 5.5V

VOUT1

2.5V

200mA

10µF

LTC3541 Typical Application

10µF

2.2µH

VIN

ENVLDO ENBUCK

SW

LVOUT

LVIN LTC3541

22pF 243k

LFB

BUCKFB

MODE

115k PGND

GND

412k

VOUT2

1.5V

300mA

2.2µF

150k

3541 TA01a

100

1

90

EFFICIENCY

80

0.1

70

60

50

POWER LOSS

0.01

40

30

20

10 VIN = 3.3V

0 VOUT = 2.5V

1

10

100

LOAD CURRENT (mA)

0.001

0.0001

1000

3541 TA01b

3541fb

For more information www.linear.com/LTC3541

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