LTC3541-2(RevA) 查看數據表（PDF） - Linear Technology

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LTC3541-2
(Rev.:RevA)

High Efficiency Buck + VLDO Regulator

Linear Technology 

LTC3541-2

High Efficiency

Buck + VLDO Regulator

FEATURES

DESCRIPTIO

■ High Efficiency, 500mA Buck Plus 300mA VLDO

Regulator

Auto Start-Up Powers Buck Output Prior to VLDO/

Linear Regulator Output

■ Independent 500mA High Efficiency Buck

(VIN: 2.7V to 5.5V)

■ 300mA VLDO Regulator with 30mA Standalone Mode

■ No External Schottky Diodes Required

■ Fixed Buck Output Voltage: 1.875V

■ VLDO Input Voltage Range (LVIN: 1.6V to 5.5V)

■ Fixed VLDO Output Voltage: 1.5V

■ Selectable Fixed Frequency, Pulse-Skip Operation

or Burst Mode® Operation

■ Short-Circuit Protected

■ Current Mode Operation for Excellent Line and Load

Transient Response

■ Shutdown Current: <3µA

■ Constant Frequency Operation: 2.25MHz

■ Low Dropout Buck Operation: 100% Duty Cycle

■ Small, Thermally Enhanced, 10-Lead (3mm × 3mm)

DFN Package

U

APPLICATIO S

■ Digital Cameras

■ Cellular Phones

■ PC Cards

■ Wireless and DSL Modems

■ Other Portable Power Systems

The LTC®3541-2 combines a synchronous buck DC/

DC converter with a very low dropout linear regulator

(VLDOTMregulator) and internal feedback resistor networks

to provide two output voltages from a single input volt-

age with minimal external components. When configured

for dual output operation, the LTC3541-2’s auto start-up

feature will bring the 1.875V buck output into regulation

in a controlled manner, prior to enabling the 1.5V VLDO

output without the need for external pin control. The

1.5V VLDO/linear regulator output prior to 1.875V buck

output sequencing may also be obtained via external pin

control. The input voltage range is ideally suited for Li-Ion

battery applications powering sub-3.3V logic from 5V or

3.3V rails.

The synchronous buck converter provides a high efficiency

output, typically 90%. It can provide up to 500mA of 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 output current

using only a 2.2µF ceramic capacitor. The input supply

voltage of the VLDO regulator (LVIN) may come from the

buck regulator output or a separate supply.

, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology

Corporation. 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 APPLICATIO

VIN

2.9V TO 5.5V

2.2µH

VOUT1

1.875V

200mA

10µF

SW ENVLDO

VIN

MODE

LTC3541-2

ENBUCK GND

VOUT

LVIN

LVOUT

PGND

VOUT2

1.5V

2.2µF 300mA

35412 TA01a

Buck (Burst) Efficiency vs Load Current

100

1

VIN = 3V

90

EFFICIENCY

80

0.1

70

60

POWER LOSS

50

0.01

40

30

0.001

20

10

0

0.0001

1

10

100

1000

LOAD CURRENT (mA) 35412 TA01b

35412fb



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